Réalisations refrigeration Co2

Réalisations refrigeration Co2

LE GROUPE CSC IMPLANTE AU IGA DES SOURCES CAP‐ROUGE SON SYSTÈME DE

RÉFRIGÉRATION ÉCOLOGIQUE UNIQUE AU MONDE
Les émissions de GES du tout nouveau Eco2‐System sont de 3900 fois inférieures à celles des
technologies actuelles sur le marché
Les Côteaux (Québec), le 25 novembre 2009 – Le propriétaire du supermarché IGA des

Sources Cap‐Rouge, M. Alain Gagné, ainsi que le président du Groupe CSC, M. Serge Dubé,

ont inauguré le 18 novembre dernier le tout nouveau supermarché IGA des Sources Cap‐

Rouge, doté du système de réfrigération écologique, l’Eco2‐System. Unique au monde, lesystème développé par le Groupe CSC utilise le CO2 en tant que réfrigérant et permet une

forte réduction des émissions de gaz à effet de serre jusqu’à 3900 fois inférieures aux

émissions des technologies actuelles sur le marché.

L’immense établissement, d’une superficie de 42 800 pieds carrés construit au coût de

quinze millions de dollars présente un concept hautement innovateur, grâce entre autres à

de toutes nouvelles configurations des rangées d’épicerie permettant une circulation

facilitée du client. Le nouveau concept du magasin prévoit également des emplacements de

boutiques repensés afin de diversifier l’expérience d’achat du consommateur.

« Nous sommes très heureux d’être partie intégrante de l’ouverture de ce supermarché, qui

à l’image de l’Eco2‐System, redéfinira les façons de faire de l’industrie pour les années à

venir. Notre équipe ainsi que celle de M. Gagné avons cru fermement dans les avantages

qu’offraient le CO2 en tant que réfrigérant, soit une meilleure performance de réfrigération

sans émettre de gaz à effet de serre et en récoltons aujourd’hui les dividendes », s’est réjoui

M. Dubé.

De son côté, M. Gagné ne cachait pas son enthousiasme, « nous voulions construire une

épicerie au concept révolutionnaire. Une telle vision impliquait nécessairement de nouvelles

approches à tous les niveaux du projet, que ce soit la configuration des rangées, le choix des

matériaux ou le design des lieux. Toutefois, l’impact de nos activités sur l’environnement

revêtait une importance capitale. Nous sommes donc très fiers d’offrir à nos clients un

système de réfrigération totalement non polluant ».

D’autres parts, les équipes de Messieurs Dubé et Gagné ont compté sur SD Réfrigération

pour assurer l’installation de l’Eco2‐System au IGA des Sources à Cap‐Rouge. L’ntreprise,

partenaire d’ffaires du Groupe CSC pour la région de Québec, possède les compétences

techniques ainsi que le réseau nécessaires pour assurer la vente et l’mplantation de ce

système unique fonctionnant au CO2 dans les supermarchés et autres établissements

commerciaux.

Écologique et meilleure efficacité énergétique
Le nouveau système développé par le Groupe CSC utilise le CO2, un gaz qu’on associe

généralement au réchauffement de la planète, mais qui devient par l’entremise de la

technologie innovatrice de la Société, un véritable ami de l’environnement en permettant

une réduction marquée des GES. En effet, le CO2 utilisé en tant que réfrigérant a un impact

sur le réchauffement climatique très inférieur aux réfrigérants synthétiques. De plus, un

système de réfrigération utilisant le dioxyde de carbone contient une moins grande quantité

de réfrigérant en raison de sa capacité volumétrique qui est de 6 à 8 fois supérieure à celle

des réfrigérants synthétiques tout en assurant une conservation et une fraîcheur optimale

des aliments.

L’équivalent de deux millions d’automobiles de moins sur nos routes
Par ailleurs, l’Eco2‐System comporte un procédé de récupération de la chaleur permettant

aux détaillants en alimentation d’liminer le besoin de recourir à un système de chauffage

conventionnel pour tout leur établissement. De ce fait, si les 6500 détaillants en

alimentation existant au Canada qui utilisent des systèmes de réfrigération conventionnels,

responsables d’mportantes émissions de gaz à effet de serre, remplaçaient ces systèmes par

l’Eco2‐System, nous pourrions observer une baisse des quantités d’émissions équivalant au

retrait de plus de deux millions d’automobiles sur nos routes.

À propos du Groupe CSC

Fondée en 1982, le Groupe CSC est une entreprise spécialisée dans le développement de

systèmes de réfrigération destinés aux détaillants en alimentation ainsi qu’au secteur

industriel. Au fil des années, l’entreprise a mis au point différents systèmes pour répondre

aux besoins variés de ses clients, en s’appuyant sur sa plateforme technologique brevetée

SMARTREFMC. Dans le domaine de l’alimentation, la Société s’est positionnée comme un

leader en Amérique du Nord, grâce à sa grande capacité d’innovation ainsi que par la

qualité, la performance et la fiabilité de ses produits. Basée à Les Côteaux, la Société

compte, par l’entremise de ses différentes unités affiliées, quelque 130 employés.

Co2A colorless, odorless, incombustible gas, CO₂, formed during respiration, combustion, and organic decomposition and used in food refrigeration, carbonated beverages, inert atmospheres, fire extinguishers, and aerosols. Also called carbonic acid gas. Carbon dioxide (CO2) is not new to refrigeration systems. Alexander Twining proposed using CO2 as a refrigerant in a British patent granted him in 1850. Thaddeus S.C. Lowe, perhaps best known for his experimentation with CO2 military balloons, designed an ice machine using CO2 in 1867. Lowe also developed a machine for marine transportation of frozen meat.The use of CO2 became more and more prevalent, peaking in the period from 1920 to 1940, and waning thereafter due to technical problems with the high pressures and leaks. Then DuPont began successfully marketing CFC refrigerants.In the 1990s there was renewed focus on the advantages of CO2. Concerns with ODP (ozone depletion potential) and GWP (global warming potential) began to result in restrictions on the use of CFCs and HFCs and in restrictive charge limits for large ammonia systems
A single-stage, subcritical CO2 system is simple but it has the disadvantages of high pressure and a limited temperature range.Transcritical (supercritical) CO2 systems are interesting for specific smaller applications - less than 3 TR - where the high system pressures can be safely engineered at reasonable cost. The automobile industry is concluding a number of air-conditioning research projects and is preparing for introduction of the technology in few years. Commercial applications are being investigated, and the components needed are currently being developed, based on many years of research. Focus is presently on hot water heat pumps and commercial sales equipment.Hybrid systems are the most common designs used in industrial refrigeration because the pressure can be limited to a level where the requirements for components like compressors, controls, and valves differ only slightly from those of traditional industrial refrigeration plants.CO2 systems can be designed in different configurations: direct expansion (DX), pump circulating, secondary brine, and combinations of these. Descriptions of some common industrial systems follow.

CO2 In Industrial Systems

Figure 3 shows a low-temperature refrigeration system (-40 degrees) that uses CO2 as a phase-change refrigerant in a cascade system with ammonia on the high-pressure side.

Figure 3. A typical R-717/CO2 cascade system.

The CO2 system is a pump circulating system where liquid CO2 is pumped from the receiver to the evaporator, where it is partly evaporated before it returns to the receiver. The evaporated CO2 is compressed in a CO2 compressor, and condensed in the CO2-NH3 heat exchanger. The heat exchanger acts as an evaporator in the NH3 system.Figure 4 shows the same system as in Figure 3, but includes a CO2 hot gas defrosting system. Figure 5 shows a low temperature refrigeration system (-40 degrees) using CO2 as a brine system with ammonia on the high-pressure side.

Figure 4. A typical R-717/CO2 cascade system with hot gas defrost.

Figure 5. A typical R-717/CO2 brine system.

The CO2 system is a pump circulating system, where the liquid CO2 is pumped from the receiver to the evaporator. Here it is partly evaporated before it returns to the receiver. The evaporated CO2 is then condensed in the CO2/NH3 heat exchanger. The heat exchanger acts as an evaporator in the NH3 system.Figure 6 shows a mixed configuration with both flooded and DX subsystems. Mixed systems are found in applications like supermarkets, where two temperature levels are required.

Design Pressure

Figure 6. A typical CO2 cascade system with two temperature levels.

There are two important factors to take into consideration when determining the design pressure of a CO2 system: high off-cycle pressure and defrost pressure when hot gas defrost is used.Off-cycle pressure can be very high. This challenge can be met in several ways:· A small, separate refrigeration system can be used to keep the liquid temperature at levels where saturated pressure is less than design pressure. This is the most common solution for industrial refrigeration applications.· The system expansion vessel can be of a volume that prevents the pressure from exceeding the design pressure.· The system can be designed to withstand the saturated pressure at the design temperature (approximately 1,160 psig).Defrosting pressure during hot gas defrosting must also be taken into consideration.No single defrost method predominates. Natural, water, electrical and CO2 hot gas defrosting are all used, depending on the system and on the availability of suitable compressors and other components.Of the various defrost strategies, CO2 hot gas is the most efficient, especially at low temperatures, but it also has the highest pressure demand. With a design pressure of Psat = 725 bar, it is possible to reach a defrosting temperature of 48 degrees to 50 degrees. The saturated pressure at 48 degrees is 636.7 psig. By adding 10 percent for the safety valves and approximately 5 percent for pressure peaks, the requirement is for pressure Psat of approximately 725 psig.

Efficiency

CO2/NH3 cascade systems re-quire a heat exchanger. Introducing exchangers creates a loss in system efficiency due to the necessity of having a temperature differential between the fluids. But compressors running with CO2 have greater efficiency and heat transfer is greater. The overall efficiency, therefore, of a CO2/NH3 cascade system is not lower when compared to that of a traditional NH3 system. Next Month: In the second article in this series on CO2 as a refrigerant, the authors will discuss system compatibility considerations including oils, water effects, leak potential, and safety with regard to CO2 refrigeration systems. Vestergaard is R&D manager for Danfoss Industrial Refrigeration; Robinson is in technical communications in the Air-Conditioning & Refrigeration Division, Danfoss Inc. Publication date: 10/06/2003

The U.S. with its huge consumption of fossil fuels, (the U.S. produces nearly 25% of man-made carbon dioxide emissions worldwide). also is experiencing the greatest increase in CO2. Actually, CO2 accounts for 80-85% of the heat trapping (greenhouse) gases contributing to global warming.

The idea that is now called the “Greening Theory” holds that all this extra CO2 is good. It will result in increased plant growth and thus in resulting increases in food supplies. There is some merit to this theory but there are numerous downsides too.

Before you assume this is another boring article on new refrigerants, what if I told you that air, water, and other everyday compounds can run your air-conditioner or refrigerator quite well? That’s a thermodynamic fact, and one of those everyday chemicals is so common that it constitutes what we all exhale—carbon dioxide (CO2).

The use of CO₂ as a refrigerant dates back more than a century, but it fell out of favor in the air-conditioning and refrigeration industry with the development of chlorofluorocarbons (CFCs) in the 1930s. Shortly thereafter, hydrochlorofluorocarbons (HCFCs) such as HCFC-22 were developed, and HCFC-22 eventually became the primary refrigerant for stationary air-conditioning systems. However, when concerns about the depletion of the stratospheric ozone layer emerged in the 1970s, national and international agreements were enacted to phase out CFCs and HCFCs. At first, the phaseout of chlorine-containing refrigerants such as CFCs and HCFCs led the industry toward another class of fluorocarbon refrigerants, hydrofluorocarbons (HFCs) that did not contain chlorine and thus did not harm the ozone layer. However, in the 1980s, scientists identified global warming as a major environmental threat, and the global warming impact of HFCs came under scrutiny, leading many researchers and manufacturers to reconsider “natural” refrigerants such as CO₂, hydrocarbons, and ammonia, because these substances have negligible direct global-warming impact and ozone-depletion potential. The signing and ratification by many countries of the Kyoto Protocol has provided greater impetus to look for alternatives to fluorocarbon refrigerants; several European countries have already begun restricting their use and are planning for an eventual phaseout. Carbon dioxide is non-flammable and non-toxic in contrast to other natural refrigerants—hydrocarbons (flammable) and ammonia (flammable and toxic). Furthermore, it is inexpensive, widely available worldwide from numerous suppliers, and not subject to venting restrictions. The high operating pressures of CO₂ also provide a potential opportunity for system size and weight reduction. The major challenge, however, is to design a cost-effective, efficient, reliable system that accommodates the unique characteristics of CO₂, most significantly, five times the typical system operating pressure and a low critical temperature that requires cooling a supercritical fluid rather than condensing a two-phase mixture. The application areas attracting the most interest today for CO₂ are those where current system refrigerant leakage rates are high enough to attract regulatory attention, as well as in high-temperature heat-pump applications and in military cooling systems because of special logistics considerations. Centralized refrigeration systems used in supermarkets are prone to leakage due to the large number of refrigerant line joints, long runs of refrigerant piping, and frequent thermal cycling. Carbon Dioxide can be used efficiently in these systems, and some leakage can be tolerated. The same is true for vehicular air-conditioning, where considerable engineering effort has been expended by the major automobile manufacturers to develop prototype CO₂-based air-conditioners for cars and trucks. (Another potential advantage of the CO₂ cycle for vehicles is a heat-pump mode that delivers instant heat in winter.) In Japan, CO₂-based heat-pump water heaters have been commercialized, and design efforts are underway in the U.S. These heat pumps take advantage of the high-temperature heat rejection from the transcritical CO₂ cycle. However, there is a downside to using CO₂ as a refrigerant. Many studies, both theoretical and experimental, have demonstrated that the thermodynamic efficiency of transcritical CO₂ cycles is lower than that of conventional fluorocarbon-based vapor compression systems, particularly at high ambient temperatures. This decrease in system efficiency could negate part or all of the environmental advantage of the CO₂ system by increasing its indirect contribution to global warming due to the higher energy consumption. Furthermore, it would likely be unacceptable from a marketing or regulatory standpoint to introduce new air-conditioning and refrigeration systems with lower efficiencies than existing units. Therefore, an approach to improving the efficiency must be found in order to spur commercialization. Fortunately, such an opportunity exists by recovering the losses that occur during the expansion process as the refrigerant leaves the high-pressure gas cooler and enters the evaporator. In theory, recovery of energy lost during the expansion process in a vapor compression cycle is of interest for any refrigerant. However, the relatively large expansion losses attributable to the high operating pressures of CO₂ make a work-recovery device particularly important. Design studies at my company have found that a reasonably efficient CO₂ expander based on scroll technology can improve the efficiency of a CO₂-based system to parity with fluorocarbon-based equipment while achieving the aforementioned environmental benefits described. With these potential benefits, why aren’t we seeing more research or accelerated efforts by manufacturers to get CO₂ on the market sooner? The answer, of course, is that history has shown us that introducing new refrigerants is never easy. However, expect to see systems that accommodate the unique characteristics of CO₂ as a “green” refrigerant in the years ahead.

Dick Topping

Dick Topping is director of Appliance Research at TIAX LLC (www.tiaxll.com). He can be reached by phone at 617/49..., by fax at 617/498-7206, or e-mail at Topping.R@tiaxllc.com. From the Top appears bimonthly in APPLIANCE ENGINEER®.

By Jorgen Bargsteen Møller, manager of special projects, training, & education, Danfoss A/S(Nordborg, Denmark) and Max Robinson, Technical Communications, Danfoss Inc. (Baltimore).This article was fi rst published in The air condition - heating - refrigeration magazine The NEWSthe 8th of December 2003 - www.achrnews.com.CO2 is keeping Supermarkets CoolIn two recent articles, the background and attributes of carbondioxide (CO2, R-744) as a refrigerant and its application in cascadesystems for industrial refrigeration were discussed. (See “CO2 inRefrigeration Applications,” Oct. 6, 2003, and “CO2 in IndustrialRefrigeration,” Nov. 3, 2003.) The following article presents a casestudy of a cascade system in a commercial application where everyevaporator operates with CO2. This system has been in operationfor two years in a 21,500-square-foot supermarket in suburbanCopenhagen.The store has 18 low- and 36 medium- and high-temperaturefi xtures. There are now 10 such installations in Europe, all circuitsoperating with subcritical CO2 cycles. There are an additional 10 to12 stores with CO2 used for low-temperature fi xtures and R-404Aused for medium- and high-temperature fi xtures.Bitzer Octagon-K compressors are used for the CO2 cycle, the low stage in thecascade.The store’s inside ambient temperature is controlled to 69.8°F(21°C) during daytime open hours, and to 64.4°F (18°C) at night.Outdoor ambient temperature ranges during the year from 14°F to86°F. Fresh air ventilation is completely suffi cient for cooling duringthe summer months, and in winter the store is warmed entirely byheat reclaim, although in some other similar installations wherewinter ambients are low, auxiliary heat must be used because of theCO2 system’s high effi ciency.In Europe, meeting the requirements of the Kyoto Protocol hasbecome increasingly important. CO2 has absolutely zero ozonedepletion eff ect, and its global warming potential is negligible inthe amounts used for industrial and commercial refrigeration. Thereis a decided trend away from HFC refrigerants.HFCs are being used, but in restricted amounts. Heavy taxes on HFCs,equivalent to $35 to $59 per 2.2 pounds, add considerable urgencyto the trend toward natural refrigerants. Natural refrigerants likeCO2 (and the hydrocarbons), with no environmental consequences,are tax free, and they are increasingly being looked upon as a longtermsolution.Because CO2 is a high-pressure refrigerant, normal commercialrefrigeration systems have to be of a cascade design, with anotherrefrigerant being used in the high stage. Hydrocarbons have beenevaluated for use as the high-stage refrigerant, but they are not currentlybeing used in large supermarket installations.Because of the taxes on HFCs and the lower cost of CO2 installations,an increasing number of smaller markets and supermarkets are beinginstalled using natural refrigerants in Germany, Luxembourg,Denmark, and other European countries.A Danfoss Case Study Examines a CascadeSystem Using CO2 and R-404A.Fig 1. A detailed representation of the cascade system, including the electronic and mechanical Danfoss controls used.Article - CO Page 1 of 3 2 is keeping supermarkets cool - 20031208

CO2 Refrigeration Systems

The use of carbon dioxide as a refrigerant has seen increasing interest in recent years. As a result, there is also a lack of familiarity with this refrigerant among the general industry. The use of CO2 in conventional refrigeration systems presents several interesting properties that must be addressed. The pressure/temperature relationship of this refrigerant is one of the primary concerns.

For an example of the pressure/temperature relationship of CO2 as vapor pressure curves see IP units or SI units (PDF files). The pressures observed with the use of CO2 are much higher than those normally found in ammonia refrigeration systems. Due to the higher pressures found with the use of carbon dioxide it becomes necessary to implement certain principles to limit the pressure increases at higher temperatures. Some of these design guidelines are used to allow standard refrigeration components to be utilized in CO2 refrigeration systems.A cascade refrigeration system is one method to provide this capability. In this process a separate refrigeration system uses a different refrigerant to condense the CO2. The CO2 is maintained at relatively low pressures by the low temperatures created by the separate refrigeration system. With this type of system configuration, standard refrigeration components are used in the CO2 refrigeration system.It is common to find ammonia (NH3 or R-717) being used as the higher temperature refrigerant to condense the CO2 used in the lower temperature refrigeration system. Below is an example of a typical CO2/NH3 cascade system in a basic configuration.

It is also important to be aware of other concerns in the event of power outages, or intermittent operation of CO2 systems. If the ammonia system is not able to provide cooling of the CO2, the resulting pressure increase in the CO2 system may cause relief valves to lift. This can release CO2 to the atmosphere and result in loss of the operating refrigerant charge. In order to maintain the pressure of the CO2 system below the maximum allowable design pressure of the CO2 system other design requirements may become necessary.According to the safety and environmental regulations in the USA refrigeration systems having a threshold quantity of ammonia greater than 10,000 pounds have specific criteria to meet for compliance. The use of CO2 for these low temperature applications provide one means of limiting the total ammonia inventory.Please Contact Us if you would like to learn more about the use of CO2 as a refrigerant. Read more about industrial refrigeration systems and specific properties of commonly used refrigerants.

CO2 Refrigeration systems

Even though Hydrofluoro compounds (HFC) are widely used as refrigerants because of their environment friendly nature (no damage to ozone layer), CO2 is also a popular choice as refrigerant. Some of the advantages of CO2 as a refrigerant are:

widely available;
high volumetric cooling capacity and heat transfer;
no recovery or recycling required;
non inflammable and non toxic;
environment friendly;
the compressors are compact in size

Some of the difficulties is using CO2 as refrigerant are: high working pressure and large pressure difference (3 to 5 times conventional refrigerants); low theoretical efficiency with normal refrigeration systems. Hence it requires advanced technology compressor and refrigeration system. The hoses need to be strong as well as the evaporators and gas coolers are used instead of condensers as there is no phase change of the refrigerant. They are widely used in vending machines.

One of the difficulties of CO2 as a refrigerant is its detection and level control.Chemical sensor elements cannot reliably measure CO2 levels. Other alternate detectors include infrared sensors.Infrared sensors can measure CO2 levels across a wide range of sensitivity. Infrared sensors are available for measuring 0ppm to 3000ppm up to 100% by volume.

In a typical electronic CO2 level control system, when the sensor detects the CO2 refrigerant level is below a threshold value, it sends a signal to the control system. The control system actuates a valve that lets in CO2 from a storage tank.The supply is stopped when the sensor detects that the CO2 level has reached the upper limit. Carbon dioxide systems have a higher likelihood of leakage than traditional refrigerant systems.As there is less charge in a vapor compression system using carbon dioxide as the refrigerant, a leak has a greater influence on system performance. Hence CO2 level control systems play an important role in operation of the refrigerant system.

Copyright 2008-2009 - Teklab S.r.l. - Via Emilia Ovest INTRODUCTION The effects of refrigerants on the environment are well documented. Supermarkets contribute both directly and indirectly to global warming. Directly, greenhouse gas emissions occur through the leakage f HFC refrigerants used in refrigeration systems for refrigeration of food. These refrigerants have very high global warming potential with GWP’s in excessof 1000. However, supermarkets also indirectly produce CO2 as they are large consumers of electricity, consuming as much as 15 000 GWh (54000TJ) per annum and approximately 40% of this is consumed by refrigeration equipment. Over the last 20 years, legislation has prohibited the use of many ozone-depleting refrigerants including CFCs and HCFCs, however, the use of HFC refrigerants is still legal and commonplace. In recent years natural refrigerants have been proposed as an environmentally friendly solution for the refrigeration industry. These refrigerants which include ammonia, hydrocarbons and carbon dioxide, do not contribute to ozone depletion and have low global warming potentials. Carbon dioxide offers a long-term solution suitable for many applications in refrigeration and heating, from domestic applications utilizing heat pumps, to providing hot water and heating to commercial applications for supermarket refrigeration. The technology is future proof requiring no further retrofitting to the next refrigerant “solution” promoted commercially.To investigate the performance of R-744 refrigeration, a prototype system was constructed and tested to demonstrate proof of principle. Advance Proof. Private to membersCopyright © 2007 The Institute of RefrigerationNo publication or reprinting without authority The authors would like to thank Tesco StoresLimited for their permission to publish this paper. Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas commonly added to water to make soda water. Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas -sublimation- in normal atmospheric conditions without going through a wet liquid stage. Therefore it gets the name "dry ice."As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. This sublimation continues from the time of purchase, therefore, pick up Dry Ice as close to the time needed as possible. Bring an ice chest or some other insulated container to hold the Dry Ice and slow the sublimation rate. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice. It is best not to store Dry Ice in your freezer because your freezer's thermostat will shut off the freezer due to the extreme cold of the Dry Ice! Of course if the freezer is broken, Dry Ice will save all your frozen goods. Commercial shippers of perishables often use dry ice even for non frozen goods. Dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice (H2O). It is often mixed with regular ice to save shipping weight and extend the cooling energy of water ice. Sometimes dry ice is made on the spot from liquid CO2. The resulting dry ice snow is packed in the top of a shipping container offering extended cooling without electrical refrigeration equipment and connections.This informative site is supported by the manufacturers and sellers of Dry Ice. Thank you for supporting them.

Carbon dioxide could replace
global-warming refrigerant

WEST LAFAYETTE, Ind. – Researchers are making progress in perfecting automotive and portable air-conditioning systems that use environmentally friendly carbon dioxide as a refrigerant instead of conventional, synthetic global-warming and ozone-depleting chemicals.It was the refrigerant of choice during the early 20th century but was later replaced with manmade chemicals. Now carbon dioxide may be on the verge of a comeback, thanks to technological advances that include the manufacture of extremely thin yet strong aluminum tubing.Engineers will discuss their most recent findings from July 25 to 28, during the Gustav Lorentzen Conference on Natural Working Fluids, one of three international air-conditioning and refrigeration conferences to be held concurrently at Purdue University. Unlike the two other conferences, the biannual Gustav Lorentzen Conference, which is being held for the first time in the United States, focuses on natural refrigerants that are thought to be less harmful to the environment than synthetic chemical compounds."The Gustav Lorentzen Conference focuses on substances like carbon dioxide, ammonia, hydrocarbons, air and water, which are all naturally occurring in the biosphere," says James Braun, an associate professor of mechanical engineering at Purdue who heads the organizing committee for all three conferences. "Most of the existing refrigerants are manmade."Purdue engineers will present several papers detailing new findings about carbon dioxide as a refrigerant, including:• Creation of the first computer model that accurately simulates the performance of carbon-dioxide-based air conditioners. The model could be used by engineers to design air conditioners that use carbon dioxide as a refrigerant. A paper about the model will be presented on July 26 during a special session sponsored by the U.S. Army in which researchers from several universities will present new findings.• The design of a portable carbon-dioxide-based air conditioner that works as well as conventional military "environmental control units." Thousands of the units, which now use environmentally harmful refrigerants, are currently in operation. The carbon dioxide unit was designed using the new computer model. A prototype has been built by Purdue engineers and is being tested.• The development of a mathematical "correlation," a tool that will enable engineers to design heat exchangers – the radiator-like devices that release heat to the environment after it has been absorbed during cooling – for future carbon dioxide-based systems. The mathematical correlation developed at Purdue, which will be published in a popular engineering handbook, enables engineers to determine how large a heat exchanger needs to be to provide cooling for a given area.• The development of a new method enabling engineers to predict the effects of lubricating oils on the changing pressure inside carbon dioxide-based air conditioners. Understanding the drop in pressure caused by the oil, which mixes with the refrigerant and lubricates the compressor, is vital to predicting how well an air conditioner will perform.Although carbon dioxide is a global-warming gas, conventional refrigerants called hydrofluorocarbons cause about 1,400 times more global warming than the same quantity of carbon dioxide. Meanwhile, the tiny quantities of carbon dioxide that would be released from air conditioners would be insignificant, compared to the huge amounts produced from burning fossil fuels for energy and transportation, says Eckhart Groll, an associate professor of mechanical engineering at Purdue.Carbon dioxide is promising for systems that must be small and light-weight, such as automotive or portable air conditioners. Various factors, including the high operating pressure required for carbon-dioxide systems, enable the refrigerant to flow through small-diameter tubing, which allows engineers to design more compact air conditioners. More stringent environmental regulations now require that refrigerants removed during the maintenance and repair of air conditioners be captured with special equipment, instead of being released into the atmosphere as they have been in the past. The new "recovery" equipment is expensive and will require more training to operate, important considerations for the U.S. Army and Air Force, which together use about 40,000 portable field air conditioners. The units, which could be likened to large residential window-unit air conditioners, are hauled into the field for a variety of purposes, such as cooling troops and electronic equipment."For every unit they buy, they will need to buy a recovery unit," Groll says. "That's a significant cost because the recovery unit is almost as expensive as the original unit. Another problem is training. It can be done, but it's much more difficult than using carbon dioxide, where you could just open a valve and release it to the atmosphere."The recovery requirement would not apply to refrigerants made from natural gases, such as carbon dioxide, because they are environmentally benign, says Groll, who estimates that carbon dioxide systems probably will take another five to 10 years to perfect.Carbon dioxide was the refrigerant of choice a century ago, but it was later replaced by synthetic chemicals."It was actually very heavily used as a refrigerant in human-occupied spaces, such as theaters and restaurants, and it did a great job," says Groll, who is chair of the Gustav Lorentzen Conference.But one drawback to carbon dioxide systems is that they must be operated at high pressures, up to five times as high as commonly seen in current technology. The need to operate at high pressure posed certain engineering challenges and required the use of heavy steel tubing.During the 1930s, carbon dioxide was replaced by synthetic refrigerants, called chlorofluorocarbons, or CFCs, which worked well in low-pressure systems. But scientists later discovered that those refrigerants were damaging the Earth's stratospheric ozone layer, which filters dangerous ultraviolet radiation. CFCs have since been replaced by hydrofluorocarbons, which are not hazardous to the ozone layer but still cause global warming.However, recent advances in manufacturing and other technologies are making carbon dioxide practical again. Extremely thin yet strong aluminum tubing can now be manufactured, replacing the heavy steel tubing.Carbon dioxide offers no advantages for large air conditioners, which do not have space restrictions and can use wide-diameter tubes capable of carrying enough of the conventional refrigerants to provide proper cooling capacity. But another natural refrigerant, ammonia, is being considered for commercial refrigeration applications, such as grocery store display cases, Groll says.Engineering those systems is complicated by the fact that ammonia is toxic, requiring a more elaborate design in which the ammonia refrigerant is isolated from human-occupied spaces. The first ammonia systems are currently being tested in Europe, and results will be presented during the Gustav Lorentzen Conference, Groll says.Groll's work is funded by the U.S. Army, Air Force and the American Society of Heating, Refrigerating and Air-Conditioning Engineers.Sources: Eckhard Groll So far, two supermarket locations have adopted a new carbon dioxide-based cascade refrigeration system that is said to help limit the use of HCFC refrigerants.A new College Park, Ga., location of Food Lion is using the new refrigeration system, which uses CO2 as a secondary refrigerant, Supermarket News reports. Food Lion plans a second location using the system in December in Columbia, S.C. The system was provided by Kysor Warren.Food Lion is using new CO2 refrigeration units to help it gain Energy Star status for its stores, according to a press release (PDF). Food Lion is one of the nation’s largest partners in the EPA Green Chill program, which encourages energy savings and emissions reduction in store chillers.A Price Chopper location in Schenectady, N.Y., was the first to receive such a system, according to a press release (PDF).Secondary loop CO2 systems are manufactured by Hill Phoenix, which only recently received EPA approval to use CO2 as a replacement for hydrochlorofluorocarbon (HCFC) in retail refrigeration.The system replaces the ozone-depleting refrigerants R-22, R-507A and R-404A with CO2. The above ozone-depleting refrigerants are widely used in retail refrigeration units.Such refrigerants are known to leak up to 20-25 percent of their charge annually, according to Hill Phoenix, while CO2 is not as prone to leakage. Additionally, use of CO2 as a secondary refrigerant means that the HCFC charge can be reduced 60-90 percent.September 30, 2009 Refrigeration plants using carbon dioxide as refrigerant: measuring and modelling the solubility and diffusion of carbon dioxide in polymers used as sealing materialsBecause of increased environmental pressure, there is currently a movement away from more traditional refrigerants such as HCFC's toward refrigerants with lower global warming potential such as carbon dioxide (CO₂). However, the use of CO₂ as a refrigerant requires a refrigeration cycle with greater extremes of pressure, placing greater demands on the polymer materials used for seals and packing. In this work we have measured the solubility and diffusivity of gaseous CO₂ in two polymers used as sealing materials in CO₂ refrigeration plants. These are Hydrogenated Nitrile Butadiene Rubber (HNBR) and Ethylene Propylene Diene Monomer (EPDM) which are used in seals such as O-rings. The experiments were performed on a high-pressure microbalance. Solubility results were modelled using an equation of state for polymers (simplified PC-SAFT). The necessary polymer parameters were obtained using a previously published method. The measured results can be successfully correlated using simplified PC-SAFT. Seth Masia
SOLAR TODAY managing editorHill Phoenix, a manufacturer of large refrigeration systems in Conyers, Ga., is about to introduce a line of products using CO2 in place of hydrochlorofluorocarbon (HCF) as the heat-transfer fluid.The company today announced receiving EPA approval for the use of CO2.HCFs are used to replace ozone-damaging CFCs, which are scheduled to be banned worldwide under the Montreal Protocol by 2030. By 2o10, phase-out is to be 75% complete. But HCFs are powerful greenhouse gases and their tendency to leak from commercial freezers is a serious problem. In a press release (see below), the company's manager of R&D said CO2 will outperform HCFs, leading to an improvement in energy efficiency for refrigerators, chillers and air conditioners. Moreover, leaking systems will no longer contribute to global warming. The company said CO2 technology will be widely adopted across the industry.Hill Phoenix will introduce its CO2 freezers and display cases, targeted at grocery stores, later this year. Supermarket Refrigeration: Swiss clock improvedCO2 performanceBernd Heinbokel - 07/01/2008 THE use of CO2 in a leading Swiss supermarket is said to have shownsignificantly better performance than systems using R404AFOUNDED by Pierre Demaurex in the 1960s in Geneva, Aligro has been theundisputed number one among the bulk supermarkets in French-speaking Switzerlandfor the last 30 years.Last fall, Dominique and Etienne Demaurex, sons and successors of Pierre Demaurexopened the third Aligro market in Sion. This store boasts a total floor space of12,500m2 of which 5,000m2 is sales floor. LKS KälteSchweiz AG/LKSFroidSuisse SA, a subsidiary of Carrier/Linde Refrigeration, was responsible forthe overall refrigeration and control technology in the normal area and deepfreeze area of the supermarket. Three compressor units were supplied, as well asdisplay cases with a total sales length of 180m and equipped the nine walk-in coldrooms with floor space of approximately 200m2. In addition, Carrier/LindeRefrigeration equipped the five deep freeze cells with floor space of approximately90m2.For normal cooling, the new CO2 composite cooling system CO2OLtec by LindeKältetechnik was used. Control and monitoring of the NC compressor units, whichalso work in the transcritical area, is handled by the newly-developed EckelmannVS3000C. All sales display case evaporators and cooling room evaporators areequipped with electronic expansion valves.The required overall cooling capacity for the normal cooling area is 322 kW. It isdivided into two separate integrated refrigeration units each with identical coolingcapacities. The deep-freeze area has a cooling capacity of 67kW. Its heat isdissipated in cascade operation by CO2 evaporating directly from the normal coolingsystems. In the sales areas as well, the direct expanding carbon dioxide ensures heatdissipation in the normal as well as in the deep-freeze area.A CO2 gas cooler in V-block design is used for transferring the heat (2 x 236kW) thatneeds to be dissipated to the ambient air.Cooling rooms with CO2 supercritical and deep-freeze rooms with CO2 subcritical.Equipped with Kuba CO2 evaporatorsIn the sales areas, customers can find fresh and frozen goods in a variety of differentcooled shelving, chill counters, islands and deepfreeze combinations from the LindeEvolution 5 series, as well as in a larger number of walk-in cold rooms and deepfreeze rooms. In these areas CO2 air coolers from Kuba are used exclusively.Heat recovery is utilised throughout. Thus, hot water for heating at 2 x150 kW isavailable during the heating season and hot service water at 90kW is available yearround.In the normal cooling system, the compressor unit system was divided into twopressure areas for the dimensioning of components. The high-pressure area wasconfigured at a maximum operating pressure of 115bar. This area includes the highpressure side of the compressors, the heat recovery system, the hot gas and liquid lineto the gas cooler, all refrigeration components on the high-pressure stage, as well as aspecial high-pressure valve.The maximum operating pressure for the other system components, for example thecollector or the liquid and suction line, is only 40bar. The evaporators in the normalcooling system are optimised on the refrigerant side for CO2 for technical flowreasons and configured for the higher pressure loads. Thus, for the greater part of thesystems, standardised commercial refrigeration components could be used that amongother things can also be used in CO2 deep freezing.Running costs are important when operating a refrigeration system and the refrigerantused is of crucial importance in this regard. If high outside temperatures are assumed,then R404A is said to show clear performance advantages over CO2.“However, if the favourable thermodynamic and technical thermal characteristics ofCO2 are taken into consideration, there is a different picture,” emphasises MarcusHöpfl, manager of the Buchser subsidiary and member of the management teamof LKS KälteSchweiz AG. He cites the following reasons:• Due to better heat transfer ensured by CO2, it is possible to operate equipment at anevaporation temperature that is 2K higher compared than R404A.• With CO2 being a high pressure refrigerant, there is a saturation temperature loss inthe suction line that is reduced by 1K compared to R404A, assisting oil return to thecondensers. The CO2 condensers in the normal cooling system can be operated withvacuum pressure, corresponding in total relative to R404A to a saturation temperaturethat is 3K higher.• The special characteristics of the transcritical process control and the good heattransfer characteristics of CO2 in the gas cooler enable cooling of the pressure gasclose to ambient.• At lower air temperatures a reduction of the condensing temperature toapproximately +10°C is possible when using CO2. The reason is that a sufficientlyhigh differential pressure exists relative to the evaporation pressure due to the higherpressure level of CO2 even at these low temperatures.• The current energy consumption of NC/DF DX CO2 systems is approximately15to 20% lower than comparable NC R404A systems with refrigerant/re-coolingsystem and DF DX. The energy data are based on measurements performed overa period of 12-18 months.• Current investment costs of NC/DF DX CO2 systems are equivalent to R404A,providing the NC system is more than 220kW or the surface area of the supermarketexceeds 2,500m2.For Marcus Höpfl, the results are clear: “CO2 should be looking at an exciting futureas refrigerant. Currently its implementation in refrigeration applications is somewhatmore expensive because the necessary components are not yet being produced in thesame quantities as are produced for systems that work with fluorinated refrigerants.Currently this acts as somewhat of a brake on demand. In the future, however, therewill not be a price difference even at lower system capacities.” 1CO2 Compressors for Light Commercial Refrigeration Ricardo A. Maciel(a); Marino Bassi(b) (a) EMBRACO – Empresa Brasileira de Compressores – Joinville/SC – BrazilTel.: +55 47 3441 2762 – e-mail: rmaciel@embraco.com.br(b) EMBRACO Europe srl – Riva Presso Chieri – ItalyTel.: +39 335 737 6085 – e-mail: marino.bassi@embraco.it1. ABSTRACTHFC refrigerant has been identified as a contributing factor with regard to global warming. This fact has put pressure onmost of the refrigeration industry to replace the HFC refrigerant fluids currently employed in vapor compressionsystems. In this search for an environmental friendly technology, Carbon Dioxide (CO2) has emerged as a leadingcandidate to be a replacement for HFCs. Today there is a strong focus on CO2 potential for beverage cooling applicationalthough it is still in the preliminarily stages. Moreover, in the design of compressors to run with high pressurerefrigerants like CO2 safety aspects must be a mandatory concern. When dealing with high pressure levels, compressorcomponents have their original design adapted to withstand such a high pressures, particularly acoustical mufflers,external shell, and compression mechanism. Regarding the external shell, the design approach goes beyond acousticaland aesthetics features as mostly observed in current refrigerating compressors. In order to safely enclose thecompression mechanism the application of a proper design methodology is mandatory to safeguard the structuralintegrity of both the compressor external shell and the whole refrigerating system. Looking for acceptable, cost-effectivesafety factors, a simultaneous design approach including advanced structural mechanics techniques, experimentation,safety standards revision, and Computer Aided Engineering (CAE) tools application is mandatory. The aim of this workis to present how Embraco has been approaching the structural design of its CO2 compressor to ensure safety andreliability. Also, a comparison between a CO2 compressor under development and a standard HFC compressor has beenperformed in both calorimeter and application tests. Preliminary data have showed that a CO2 can perform competitivelyto the HFC systems in the field.2. INTRODUCTION2.1. Brief CO2 history as refrigerant for cooling and heat pumping systemThe design of a refrigeration system involves many considerations. Design invariably requires a critical evaluation of thesolutions proposed by considering factors like economics, reliability, safety and environmental impact. The vaporcompression cycle has dominated the refrigeration market to date because of its advantages: high efficiency, low cost,and simple mechanical embodiments. Despite those advantages, one of the concerns regarding the use of these systemscomes from the fact that the refrigerating effect is produced by making a volatile fluid boil at a suitably low temperature.Most of the classes of volatile fluids currently in use aggress the ozone layer, promote the global warming of the Earthor present unfavorable properties to the human health and/or safety.In recent years environmental aspects are increasingly becoming an important issue in the design and development ofrefrigeration systems. In vapor compression systems, the banning of CFCs and HCFCs because of their negativeenvironmental impacts has made way for the HFCs refrigerants. Until now there has been no motive for the refrigerationmarket to find other alternatives. As environmental concern grows, alternative technologies which use either inert gasesor no fluid at all become attractive solutions with regard to the environmental issue.In this situation HFCs seem to be only an interim solution. Looking for final choices and taking into account regulationsfor greenhouse gas emissions, natural fluids become a promising alternative as refrigerant fluids. Some of theserefrigerants like the hydrocarbons and ammonia come with safety risks. If non-toxicity and non-flammability arerequired, the focus comes to CO2, which has been considered for low capacity applications operating in transcriticalrefrigeration cycle.2.2. Application of transcritical CO2 compressorsTranscritical cycle is that one in which the compressor discharge pressure is above the refrigerant critical point and thesuction pressure is below it. In other words, condensation does not take place at the high side heat exchanger and therefrigerant vapor and liquid phases co-exist in only one distinguishable phase. Figure 1 depicts a typical CO2transcritical cycle in a pressure-enthalpy diagram. Since usual ambient temperatures can exceed 31oC (CO2 critical2temperature), a CO2 refrigerating system will not exhibit condensation at the high side heat exchanger, as shown by theheat rejection process 2-3 in the figure, and temperatures and pressures will not be linked as in saturation (dome) region.In a refrigeration cycle where conditions range from subcritical to supercritical, CO2 reaches high pressures, as much as100 bars (10 MPa) or even more at high ambient temperature and/or extreme operating conditions. Below are depictedtypical pressure differences for design conditions employing common refrigerant fluids as well as CO2.-50 50 150 250 350 45051010050031°C 55°C7°C-17°C-41°C13 2401020304050607080-50 -40 -30 -20 -10 0 10 20Evaporating Temperature [oC]Pressure Differential [bar]R134a R22R404a R600CO2(a) (b)Figure 1: (a) CO2 pressure-enthalpy diagram. (b) Pressure difference for common refrigerants and for CO2.2.3. Mainly safety and reliability issuesDespite the strong ecological appeal of CO2 refrigeration, the utilization of this compound as refrigerant fluid stilldemands solutions for some technical challenges, mainly the ones related to the high pressures associated to the CO2transcritical refrigeration cycle. The compressor structure must meet requirements anticipated by safety standardsincident in the refrigeration segment. Furthermore, taking into account the current version of those standards, therequirements for CO2 invariably will lead us to unfavorable design cost wise when comparing to the current refrigeratingcompressors design.Amongst compressor components affected by the replacement of high GWP refrigerant fluids by CO2, the external shellprobably is the one which deserves a particular attention. Since this component is developed to withstand the approvalload imposed by international codes like UL 984, and such a load is the result of a design pressure (refrigerant saturationpressure at 27oC) multiplied by a fixed constant (regardless the refrigerant fluid), one can easily reaches non-economicaldesign conditions. In the particular case of CO2 the hydrostatic approval pressure can exceed 350 bar while currentrefrigerants require 53 bar approval pressure by the same code. This requires special demands for construction material,geometry, tubing design and electrical connections development. In addition, once the shell represents a boundarybetween the refrigeration circuit and the surroundings, extreme care is to be taken in order to suit the mechanicalstrength to the design demands and with favorable safety factors weighted by safety and economics issues. 3. RELIABILITY AND SAFETY ASPECTS OF COMPRESSOR SHELL3.1. Standards EvaluationAiming to design a pressure vessel taking the advantage of some standard procedures or even good practices of than, agood approach in the design of such compressor would be make an effort to follow those specific standards for pressurevessels. Furthermore, following these standards in the very beginning of the development leads to a good assertivenessin getting results early in the development decreasing the try and failure approach time.However, some standards like the ASME code show a huge among of rules and recommendations that in most of thecases seems very conservative depending on the application. They are based on material selection, project development,manufacturing process, assembling and inspection. Unfortunately the “standard’ rules uses to avoid the applicability oreven refraining the application of the vessels in some temperatures, pressures imposing also geometric limitations likethe thickness of the shell or material selection.Since there are two different pressures level in a compressor shell for refrigeration, the discharge (high side) and suction(low side) should be design the resist these two different loads. Moreover, the experimental test should also be3performed concerning this aspect. In the IEC 60335-2-34, draft proposals for motor-compressors for R-744 intranscritical applications, the following pressures are specified for his kind of application, Table 1.Table 1 – Minimum low and high side test pressures.Pressure testTemperature MPa (bar)High Side Low SideSubcriticalCF3CH2FTranscriticalCO2For ac applicationsFor refrigerator and freezer applicationsFor heat pump applicationsR-134aR-7446,5 (65)42,0 (420)36,0 (360)39,0 (390)2,5 (25)26 (260)NOTE 103 The values given above may not be high enough for some applications.In order to analyze how other standards is dealing with these issues, the ASME pressure vessels Section VII division IIhas been considered to figure out their concerns. Some concerned parts of this such standard have taken into account inthe following compressor development and its component design, like UG-19, UG-21, and UG 99. For details see [1].3.2. Material characterizationIn order to have a well understanding of all used materials in the CO2 compressor, mainly in the shell body, a deepanalysis of standards material have been performed. Concerning the possibility of having the shell in cast, both gray castiron and nodular cast iron have been evaluated. Due the notorious superior behave of the nodular comparing to the graycast iron, this first one has been chosen as the material for the cast vessel.For the cast iron specifications, the following ASME standard has been analyzed and token into account: ASME Boilerand Pressure Vessel Code, Section VIII, Division 1, Rules for Construction of Pressure Vessels, 2004 edition. A briefsummary of the standard concern is depicted in Table 2Table 2 – Material specification and its restriction according the ASME code.Elongation ASME Part code Restrictions Material18% Part UCD eCode Case 1939Pdesign 7 MPaWeld is allowedSA-395Class 60-40-1815% e18%Part UCD Pdesign 7 MPaWeld is not allowedSA-39515% Part UCI Pdesign 1,1 MPaSA-278SA-47However, as can be seen in the limitation of the standard and, and due to the special material treatment to reach thespecifications above, this lead us to developed our in-house approval test and material analysis regardless the soevidence advantage in follow the ASME or whatever standard for pressure vessels.Thus, aiming to evaluate a reasonable and cost effective material and make a trade-off analysis among feasibility andsecurity, the following approach has been considered in the material development:(a) Quality and homogeneously of the present material;(b) Weld joints evaluation in order to get all of their characteristics;(c) Mechanical properties of all current used material, including the main body material, weld joint material, andwelding properties;(d) Fatigue and fracture mechanics considering its fatigue _-N and _-N curves, KIC, J and so one;(e) Experimental and a complete laboratory program to evaluate all material and its component. Validation andexperimentation program;(f) A very well developed structural analysis by finite element, FEA. Where the Project by Analysis have been takeninto a big effort.401002003004005006000 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08Deformation [mm/mm]Stress [MPa]Raw MaterialAfter thermal treatmentAfter weldingFigure 2: Stress-Strain curve for raw cast iron, after thermal treatment and after welding.4. CO2 COMPRESSOR SAFETY AND RELIABILITY RESULTSA huge amount of numerical simulations and experimental tests have been performed in order to evaluate each proposeof the compressor shell aiming to a complete envelope analysis of its safety aspect: Collapse load, Plastic hinge, Threadanalysis, Weld analysis, Hydrostatic pressure test, and Fatigue test.4.1. Compressor shellThis component is surely the most important one concerning safety issue aspect and thus, is the subject of this paper. Itencloses al other compressor components guaranteeing their hermeticity and holding the CO2 inherent high pressure.Otherwise the cylinder head is facing the highest pressure within the enclosed shell, due the area and the volume thevessel shell shall be the weak point of the design. The external view of the entire compressor vessel is depicted in Figure3, where the shell and cylinder head is shown in cast body.The shell must be design taking into account a huge amount of structural and material safety issues, regarding materialbehave, plastic analysis, collapse load, fatigue properties, plastic hinge, thread evaluation, welding analysis and so one.Following pictures and analysis depicts these security issues aiming to characterizes and analyze the pressure vesselitself and their singularities like welding and thread.Figure 3: The CO2 compressor shell 3D model and the FEA result for total deformation due an elastic collapse load evaluation.4.2. Collapse loadA plastic analysis may be used to determine the collapse load for a given combination of loads on a given structure. Thefollowing criterion for determination of the collapse load shall be used. A load–deflection or load–strain curve is plottedwith load as the ordinate and deflection or strain as the abscissa. The angle that the linear part of the load– deflection or5load–strain curve makes with the ordinate is called _. A second straight line, hereafter called the collapse limit line, isdrawn through the origin so that it makes an angle _ = tan-1 (2 tan_) with the ordinate. The collapse load is the loadat the intersection of the load–deflection or load–strain curve and the collapse limit line. If this method is used, particularcare should be given to ensure that the strains or deflections that are used are indicative of the load carrying capacity ofthe structure.The result of collapse load can be figure out on Figure 3 where the total deformation is analyzed is the most criticalpoint. Figure 4 depicts two different proposes for the shell figuring out the pressure limit for both in a collapse load nonlinear simulation. The point where the straight line crosses the deformation line figures the collapse load pressureaccording to the ASME criteria.Figure 4: Collapse Plastic evaluation of two different proposes of compressor shell.4.3. Plastic hingeA plastic hinge is an idealized concept used in Limit Analysis. In a beam or a frame, a plastic hinge is formed at thepoint where the moment, shear, and axial force lie on the yield interaction surface. In plates and shells, a plastic hinge isformed where the generalized stresses lie on the yield surface.Depending on the region of the shell, the corresponding theory should be applied in order to evaluate their safetyfactory, meanly in discontinuity region.For that design pressure, each specific transition should be analyzed concerning its Tresca Stress and whether or not thepresence of plastic hinge. See Figure 5.Figure 5: 3D stress evaluation checking the presence of general plastic hinge formation.4.4. Thread analysisSome discontinuities such the thread region have a special treat of their stress and safety factor. The stress levelthroughout the filet section should not reach a specific value regarding its failure criteria, in this case, the fourth theoryof the elasticity and Tresca theory.6Pure Shear: The average primary shear stress across a section loaded under design conditions in pure shear (forexample, keys, shear rings, screw threads) shall be limited to 0.6Sy.Figure 6: Thread analysis regarding shear and intensity stress.4.5. Weld analysisIn the design of the weld joint in a such pressure vessels like CO2 compressor, special attention have been taken tofollow or at least figure out how the ASME code deal with this kind of joint. In the code is pretty clear how the involvedprocess is taking into account, like material selection, joint type, welding process, etc, according to the so called jointefficiency denomination.Joint efficiency is defined as the ratio of strength of a joint to the strength of the base metal, expressed in percentage.In the ASME code the section in which this issue is dealt is the Part UW, requirements for pressure Vessels Fabricatedby Welding. In this section, various type of joints, like but joint and lap joint are specified with their corresponding jointefficiency. Thus, one should use the corresponding strength ratio multiplier in the design of pressure vessel using thissuch kind of welding. See Table 3Table 3– Maximum allowable joint efficiencies for Arc and Gas welded joint, from ASME code Table UW-12.Joint Type Degree of Radiographic ExaminationButt joint 1.00 0.85 0.70Single full fillet lap jointwithout plug weldsNA1 NA 0.45In the ASME code there is also a characterization of the weld joint depending on its location on the pressure vessel, forinstance, whether it’s located at main shell body, communications chambers, nozzles, or transitions in diameterincluding joints between the transition and a cylinder at either the large or small end; circumferential welded jointsconnecting formed heads other than hemispherical to main shells, to transitions in diameter, to nozzles, or tocommunicating chambers. Depending on the location, special safety aspects is also a concern.However, in order to optimize the compressor shell development, the actual weld efficiency should be evaluated andexperimental tests take place aiming to reduce the conservativeness of this such code pursuance.4.6. Hydrostatic pressure testsFor each design proposes aiming to check the extreme pressure resistance of the shell, a hydrostatic pressure testperformed. This is a complete static strength test where all the shell components, that is, the main body material andweld joint are subject to the same pressure till its burning collapse. After the collapse test, the failure component isevaluated aiming to figure out its failure mode and the condition of their parts mainly cast and welding defects. Figure7depicts a failed compressor shell after an overload hydrostatic pressure test.1 Not applicable7Figure 7: A failed compressor shell after an extreme hydrostatic pressure test figuring out the maximum allowed vessel pressure.4.7. Fatigue testsAiming to evaluate the fatigue performance of the compressor itself and also different configurations for material,welding and so one, fatigue tests have been performed in special specimen samples and in the pressure vessel.The fatigue test in the specimens has followed standardized sample tests (ASTM E399/90) and it has been cut fromwelded cast iron plates.The fatigue limits have been evaluated in different places (melted zone, heat affected zone and base metal) with specialindentation on the samples. The picture of a specimen cut from the main body of the welded shell can be seen on Figure8(b). In these pictures the specimen is subjected to fatigue load in the universal axial tension machine.(a) (b)Figure 8: (a) A fatigue test of the compressor shell running on a special developed machined (b) specimen sample cutfrom the welded main body of the compressor shell and a fatigue test running on a uniaxial universal tension machineFor the fatigue test of the final compressor shell, both high and low side of the enclosed vessel part have been submittedto pressure load according working condition for each compressor side. As a first approach to perform a fatigue test andalso to have a reasonable result in safety life, the tests have been performed according Table 1. However, even the IECcode says that those pressures could not be enough and those ones could differ depending upon the compressorapplication. Thus, some other reasonable pressure level fatigue test should take part of the shell development and thistopic is still a mandatory concern in the CO2 compressor development.A fatigue life testing running in the high pressure side of the compressor shell can be seen on Figure 8, where few shellsare submitted to a variable pressure cycle according Table 1. This is a special Embraco in house development machinedesigned concerning safety aspects for the operator. The pressure cycle loop is monitoring by software and the numberof cycles and pressure conditions data is registered.The notorious advantage of submitting the whole shell to fatigue load test is the evaluation of all vessel issues, likewelding, materials, threads, and all other possible weak points of the shell design, guaranteeing the safety factor at all.84.8. Cylinder head analysisThe same approach should be applied in the design of the cylinder head. Moreover, this component could be alsoconsidered a critical weak point since it faces the highest pressure level and also the temperature gradient. So in thecalculation of the safety factor, the stress to be considered should be that one given by the discharge pressure load plusthat one resulted by the temperature gradient.Another important weak point that should be a concern is the discontinuity resulted by the connectors. This region couldface a high stress level due the concentration factor given by the presence of a hole in a so high pressure stress region.See Figure 9.Figure 9: The stress level on a cylinder head component. Special attention should be taken in discontinuities like shape transitionsand tube holes.5. METHODOLOGY AND COMPARISON BASIS FOR PERFORMANCE TESTSSince January 2004 Embraco has been researching and developing CO2 compressors. Based on the demands required byCO2 as a refrigerant fluid, a completely new compressor platform was developed. Many CO2 compressor samples havebeen tested to date in order to assess the performance of the concept.All the results obtained in this work were compared to current HFC technology in the field. Neither the improvement oncurrent HFC refrigeration compressors nor the improvement on the appliance were considered despite the opportunitiesfor that. CO2 is applied as a drop-in, keeping the refrigeration system technology at the same level it is today. Regardingcalorimeter tests, the comparison basis is the volumetric and the compressor external isentropic efficiencies while theenergy consumption in a monthly basis constitutes the comparison parameter for the appliance tests.5.1. CO2 compressor testing program and resultsThe facilities for the CO2 compressors performance evaluation were based in a hot cycle calorimeter in which the testingprocedure consists of imposing the pressure and temperature at the compressor inlet. The discharge pressure and theambient temperature are also imposed and the parameters measured are the refrigerant mass flow rate and thecompressor power consumption. Figure 10 depicts an outline of the test rig for CO2 compressor evaluation.9Figure 10: Test rig for CO2 compressors performance evaluation.Calorimeter tests were performed at different evaporating temperatures and discharge pressures for the CO2compressors. Evaporating temperature was varied from –5oC to –15oC while the discharge pressure ranged from 83 barto 95 bar. Ambient temperature was kept constant and at 32oC. The compressor inlet temperature was also kept constantand equal to the ambient temperature.Figures 11, 12, and 13 show the performance curves for the CO2 compressor, namely cooling capacity, isentropicefficiency, and volumetric efficiency. In the same plot the respective curves for an standard HFC compressor can beseen. For the CO2 runs, the cooling capacity was calculated considering an approach of 4.6K in the gas cooling process.For the HFC curve, the condensing temperature considered was 43oC and the sub-cooling as 0.4K. The isentropic andvolumetric efficiencies were calculated as described in the appendix of this work.400500600700800900100011001200-17 -15 -13 -11 -9 -7 -5 -3Evaporating Temperature [oC]Cooling Capacity [W]CO2 (Pdisc = 83 bar) CO2 (Pdisc = 89 bar)CO2 (Pdisc = 95 bar) R134a (Tcond = 43C)Figure 11: CO2 compressor cooling capacity map.100.380.420.460.500.540.580.62-17 -15 -13 -11 -9 -7 -5 -3Evaporating Temperature [oC]Isentropic Efficiency [-]CO2 (Pdisc = 83 bar) CO2 (Pdisc = 89 bar)CO2 (Pdisc = 95 bar) R134a (Tcond = 43C)Figure 12: CO2 compressor isentropic efficiency map.0.500.550.600.650.700.750.800.85-17 -15 -13 -11 -9 -7 -5 -3Evaporating Temperature [oC]Volumetric Efficiency [-]CO2 (Pdisc = 83 bar) CO2 (Pdisc = 89 bar)CO2 (Pdisc = 95 bar) R134a (Tcond = 43C)Figure 13: CO2 compressor volumetric efficiency map.5.2. Appliances testing program and resultsThe compressor performance comparison presented in section 5.1 is very useful to understand the improvementsexpected on compressor performance when moving from the HFC-134a to CO2.However, when comparing only compressor performance in a calorimeter test some variables are not contemplated, andsome assumptions such as the approach temperature at the gas cooler outlet for the CO2 cycle or the subcooling degreeat the condenser outlet for the HFC cycle, and isenthalpic expansion process, have to be made.Therefore, an additional comparison between CO2 and HFC-134a technologies was proposed based on a finalapplication. A 405 cans storage capacity beverage vendor cabinet was chosen for that purpose. The tests were performed11at 32°C ambient temperature and 65% relative humidity for both HFC-134a and CO2. The overall system energyconsumption was measured and the contributions of the compressor and other system components (fans, lights,electronic controls) were evaluated apart. Figure 14 shows the energy consumption results for the baseline system withHFC-134a as well as with CO2.050100150200250300350400System Consumption Compressor Consumption Other System ComponentsEnergy Consumption [kWh/month]R134a CO2Figure 14: Beverage vendor energy consumption (32°C / 65%).6. CONCLUSIONThe standard evaluation and analysis is surely an excellent and mandatory approach in the design of a such kind ofCompressor. It takes the advantage of a huge experience on the development of pressure vessels, if we considered theSME for instance, but also the intrinsic experiences of each specific standard committee. Moreover, following somegood practices of those standards leads a development to be more assertive in the very beginning of the design, likematerial selection, process chosen, manufacturing issues and so on.However, the general approach of the standard leads also to a much high conservative approach in components designand safety criteria. This approach tends to not achieve an optimized design concerning material selection optimization,thickness and strength of all components and failure mode criteria resulting in a safety factor normally pretty high.Thus, an efficient way to design a such compressor would be that one where all involved issues are very well understoodand deeply analyzed. For example, instead of chose a material exactly according to the specification of the standard,what can lead to a high cost than another cheaper one, one can figure out the actual strength of the componentthroughout advanced FEA analysis and experimental verification. This approach is some call Design by Analysis insteadof that one Design by Rules.The Finite Element Analysis allows the design engineering to have a deep understanding of the component behave andto achieve a better design where each part of the structure are optimized for the such working condition. This leads to areasonable safety factor which is not so small to be hazardous but not so high than makes the compressor projectunfeasible regarding economic point of view.This Design by Analysis approach in compressor and its components development has depicted a very important pointfor discussion: the required updating of some current standards for household and light commercial compressors forrefrigerating. Mainly those one developed based upon CFC refrigerants operating in much less working pressure thanCO2.Results for isentropic and volumetric efficiency were shown for a CO2 compressor prototype and for an standard HFCcompressor currently in the field. It was found that CO2 compressor prototype can deliver better isentropic efficiencythan an HFC compressor, regardless the discharge pressure and the evaporating temperature within the ranges tested.The same conclusion could be observed for the volumetric efficiency. The gains observed with the CO2 compressorprototype varied from 45% to 50% in terms of isentropic efficiency, and from 32% to 44% in terms of volumetricefficiency. Superior compression and volumetric efficiencies can make the CO2 application feasible, overcoming theintrinsically low CO2 transcritical cycle efficiency.

widely available;
high volumetric cooling capacity and heat transfer;
no recovery or recycling required;
non inflammable and non toxic;
environment friendly;
the compressors are compact in size

Some of the difficulties is using CO2 as refrigerant are: high working pressure and large pressure difference (3 to 5 times conventional refrigerants); low theoretical efficiency with normal refrigeration systems. Hence it requires advanced technology compressor and refrigeration system. The hoses need to be strong as well as the evaporators and gas coolers are used instead of condensers as there is no phase change of the refrigerant. They are widely used in vending machines.

One of the difficulties of CO2 as a refrigerant is its detection and level control.Chemical sensor elements cannot reliably measure CO2 levels. Other alternate detectors include infrared sensors.Infrared sensors can measure CO2 levels across a wide range of sensitivity. Infrared sensors are available for measuring 0ppm to 3000ppm up to 100% by volume.

In a typical electronic CO2 level control system, when the sensor detects the CO2 refrigerant level is below a threshold value, it sends a signal to the control system. The control system actuates a valve that lets in CO2 from a storage tank.The supply is stopped when the sensor detects that the CO2 level has reached the upper limit. Carbon dioxide systems have a higher likelihood of leakage than traditional refrigerant systems.As there is less charge in a vapor compression system using carbon dioxide as the refrigerant, a leak has a greater influence on system performance. Hence CO2 level control systems play an important role in operation of the refrigerant system.

Copyright 2008-2009 - Teklab S.r.l. - Via Emilia Ovest INTRODUCTION The effects of refrigerants on the environment are well documented. Supermarkets contribute both directly and indirectly to global warming. Directly, greenhouse gas emissions occur through the leakage f HFC refrigerants used in refrigeration systems for refrigeration of food. These refrigerants have very high global warming potential with GWP’s in excessof 1000. However, supermarkets also indirectly produce CO2 as they are large consumers of electricity, consuming as much as 15 000 GWh (54000TJ) per annum and approximately 40% of this is consumed by refrigeration equipment. Over the last 20 years, legislation has prohibited the use of many ozone-depleting refrigerants including CFCs and HCFCs, however, the use of HFC refrigerants is still legal and commonplace. In recent years natural refrigerants have been proposed as an environmentally friendly solution for the refrigeration industry. These refrigerants which include ammonia, hydrocarbons and carbon dioxide, do not contribute to ozone depletion and have low global warming potentials. Carbon dioxide offers a long-term solution suitable for many applications in refrigeration and heating, from domestic applications utilizing heat pumps, to providing hot water and heating to commercial applications for supermarket refrigeration. The technology is future proof requiring no further retrofitting to the next refrigerant “solution” promoted commerciallThe authors would like to thank Tesco StoresLimited for their permission to publish this paper. Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas commonly added to water to make soda water. Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas -sublimation- in normal atmospheric conditions without going through a wet liquid stage. Therefore it gets the name "dry ice."As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. This sublimation continues from the time of purchase, therefore, pick up Dry Ice as close to the time needed as possible. Bring an ice chest or some other insulated container to hold the Dry Ice and slow the sublimation rate. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice. It is best not to store Dry Ice in your freezer because your freezer's thermostat will shut off the freezer due to the extreme cold of the Dry Ice! Of course if the freezer is broken, Dry Ice will save all your frozen goods. Commercial shippers of perishables often use dry ice even for non frozen goods. Dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice (H2O). It is often mixed with regular ice to save shipping weight and extend the cooling energy of water ice. Sometimes dry ice is made on the spot from liquid CO2. The resulting dry ice snow is packed in the top of a shipping container offering extended cooling without electrical refrigeration equipment and connections.This informative site is supported by the manufacturers and sellers of Dry Ice. Thank you for supporting them.

Carbon dioxide could replace
global-warming refrigerant

WEST LAFAYETTE, Ind. – Researchers are making progress in perfecting automotive and portable air-conditioning systems that use environmentally friendly carbon dioxide as a refrigerant instead of conventional, synthetic global-warming and ozone-depleting chemicals.It was the refrigerant of choice during the early 20th century but was later replaced with manmade chemicals. Now carbon dioxide may be on the verge of a comeback, thanks to technological advances that include the manufacture of extremely thin yet strong aluminum tubing.Engineers will discuss their most recent findings from July 25 to 28, during the Gustav Lorentzen Conference on Natural Working Fluids, one of three international air-conditioning and refrigeration conferences to be held concurrently at Purdue University. Unlike the two other conferences, the biannual Gustav Lorentzen Conference, which is being held for the first time in the United States, focuses on natural refrigerants that are thought to be less harmful to the environment than synthetic chemical compounds."The Gustav Lorentzen Conference focuses on substances like carbon dioxide, ammonia, hydrocarbons, air and water, which are all naturally occurring in the biosphere," says James Braun, an associate professor of mechanical engineering at Purdue who heads the organizing committee for all three conferences. "Most of the existing refrigerants are manmade."Purdue engineers will present several papers detailing new findings about carbon dioxide as a refrigerant, including:• Creation of the first computer model that accurately simulates the performance of carbon-dioxide-based air conditioners. The model could be used by engineers to design air conditioners that use carbon dioxide as a refrigerant. A paper about the model will be presented on July 26 during a special session sponsored by the U.S. Army in which researchers from several universities will present new findings.• The design of a portable carbon-dioxide-based air conditioner that works as well as conventional military "environmental control units." Thousands of the units, which now use environmentally harmful refrigerants, are currently in operation. The carbon dioxide unit was designed using the new computer model. A prototype has been built by Purdue engineers and is being tested.• The development of a mathematical "correlation," a tool that will enable engineers to design heat exchangers – the radiator-like devices that release heat to the environment after it has been absorbed during cooling – for future carbon dioxide-based systems. The mathematical correlation developed at Purdue, which will be published in a popular engineering handbook, enables engineers to determine how large a heat exchanger needs to be to provide cooling for a given area.• The development of a new method enabling engineers to predict the effects of lubricating oils on the changing pressure inside carbon dioxide-based air conditioners. Understanding the drop in pressure caused by the oil, which mixes with the refrigerant and lubricates the compressor, is vital to predicting how well an air conditioner will perform.Although carbon dioxide is a global-warming gas, conventional refrigerants called hydrofluorocarbons cause about 1,400 times more global warming than the same quantity of carbon dioxide. Meanwhile, the tiny quantities of carbon dioxide that would be released from air conditioners would be insignificant, compared to the huge amounts produced from burning fossil fuels for energy and transportation, says Eckhart Groll, an associate professor of mechanical engineering at Purdue.Carbon dioxide is promising for systems that must be small and light-weight, such as automotive or portable air conditioners. Various factors, including the high operating pressure required for carbon-dioxide systems, enable the refrigerant to flow through small-diameter tubing, which allows engineers to design more compact air conditioners. More stringent environmental regulations now require that refrigerants removed during the maintenance and repair of air conditioners be captured with special equipment, instead of being released into the atmosphere as they have been in the past. The new "recovery" equipment is expensive and will require more training to operate, important considerations for the U.S. Army and Air Force, which together use about 40,000 portable field air conditioners. The units, which could be likened to large residential window-unit air conditioners, are hauled into the field for a variety of purposes, such as cooling troops and electronic equipment."For every unit they buy, they will need to buy a recovery unit," Groll says. "That's a significant cost because the recovery unit is almost as expensive as the original unit. Another problem is training. It can be done, but it's much more difficult than using carbon dioxide, where you could just open a valve and release it to the atmosphere."The recovery requirement would not apply to refrigerants made from natural gases, such as carbon dioxide, because they are environmentally benign, says Groll, who estimates that carbon dioxide systems probably will take another five to 10 years to perfect.Carbon dioxide was the refrigerant of choice a century ago, but it was later replaced by synthetic chemicals."It was actually very heavily used as a refrigerant in human-occupied spaces, such as theaters and restaurants, and it did a great job," says Groll, who is chair of the Gustav Lorentzen Conference.But one drawback to carbon dioxide systems is that they must be operated at high pressures, up to five times as high as commonly seen in current technology. The need to operate at high pressure posed certain engineering challenges and required the use of heavy steel tubing.During the 1930s, carbon dioxide was replaced by synthetic refrigerants, called chlorofluorocarbons, or CFCs, which worked well in low-pressure systems. But scientists later discovered that those refrigerants were damaging the Earth's stratospheric ozone layer, which filters dangerous ultraviolet radiation. CFCs have since been replaced by hydrofluorocarbons, which are not hazardous to the ozone layer but still cause global warming.However, recent advances in manufacturing and other technologies are making carbon dioxide practical again. Extremely thin yet strong aluminum tubing can now be manufactured, replacing the heavy steel tubing.Carbon dioxide offers no advantages for large air conditioners, which do not have space restrictions and can use wide-diameter tubes capable of carrying enough of the conventional refrigerants to provide proper cooling capacity. But another natural refrigerant, ammonia, is being considered for commercial refrigeration applications, such as grocery store display cases, Groll says.Engineering those systems is complicated by the fact that ammonia is toxic, requiring a more elaborate design in which the ammonia refrigerant is isolated from human-occupied spaces. The first ammonia systems are currently being tested in Europe, and results will be presented during the Gustav Lorentzen Conference, Groll says.Groll's work is funded by the U.S. Army, Air Force and the American Society of Heating, Refrigerating and Air-Conditioning Engineers.Sources: Eckhard Groll So far, two supermarket locations have adopted a new carbon dioxide-based cascade refrigeration system that is said to help limit the use of HCFC refrigerants.A new College Park, Ga., location of Food Lion is using the new refrigeration system, which uses CO2 as a secondary refrigerant, Supermarket News reports. Food Lion plans a second location using the system in December in Columbia, S.C. The system was provided by Kysor Warren.Food Lion is using new CO2 refrigeration units to help it gain Energy Star status for its stores, according to a press release (PDF). Food Lion is one of the nation’s largest partners in the EPA Green Chill program, which encourages energy savings and emissions reduction in store chillers.A Price Chopper location in Schenectady, N.Y., was the first to receive such a system, according to a press release (PDF).Secondary loop CO2 systems are manufactured by Hill Phoenix, which only recently received EPA approval to use CO2 as a replacement for hydrochlorofluorocarbon (HCFC) in retail refrigeration.The system replaces the ozone-depleting refrigerants R-22, R-507A and R-404A with CO2. The above ozone-depleting refrigerants are widely used in retail refrigeration units.Such refrigerants are known to leak up to 20-25 percent of their charge annually, according to Hill Phoenix, while CO2 is not as prone to leakage. Additionally, use of CO2 as a secondary refrigerant means that the HCFC charge can be reduced 60-90 percent.September 30, 2009 Refrigeration plants using carbon dioxide as refrigerant: measuring and modelling the solubility and diffusion of carbon dioxide in polymers used as sealing materialsBecause of increased environmental pressure, there is currently a movement away from more traditional refrigerants such as HCFC's toward refrigerants with lower global warming potential such as carbon dioxide (CO₂). However, the use of CO₂ as a refrigerant requires a refrigeration cycle with greater extremes of pressure, placing greater demands on the polymer materials used for seals and packing. In this work we have measured the solubility and diffusivity of gaseous CO₂ in two polymers used as sealing materials in CO₂ refrigeration plants. These are Hydrogenated Nitrile Butadiene Rubber (HNBR) and Ethylene Propylene Diene Monomer (EPDM) which are used in seals such as O-rings. The experiments were performed on a high-pressure microbalance. Solubility results were modelled using an equation of state for polymers (simplified PC-SAFT). The necessary polymer parameters were obtained using a previously published method. The measured results can be successfully correlated using simplified PC-SAFT. Seth Masia
SOLAR TODAY managing editorHill Phoenix, a manufacturer of large refrigeration systems in Conyers, Ga., is about to introduce a line of products using CO2 in place of hydrochlorofluorocarbon (HCF) as the heat-transfer fluid.The company today announced receiving EPA approval for the use of CO2.HCFs are used to replace ozone-damaging CFCs, which are scheduled to be banned worldwide under the Montreal Protocol by 2030. By 2o10, phase-out is to be 75% complete. But HCFs are powerful greenhouse gases and their tendency to leak from commercial freezers is a serious problem. In a press release (see below), the company's manager of R&D said CO2 will outperform HCFs, leading to an improvement in energy efficiency for refrigerators, chillers and air conditioners. Moreover, leaking systems will no longer contribute to global warming. The company said CO2 technology will be widely adopted across the industry.Hill Phoenix will introduce its CO2 freezers and display cases, targeted at grocery stores, later this year. Supermarket Refrigeration: Swiss clock improvedCO2 performanceBernd Heinbokel - 07/01/2008 THE use of CO2 in a leading Swiss supermarket is said to have shownsignificantly better performance than systems using R404AFOUNDED by Pierre Demaurex in the 1960s in Geneva, Aligro has been theundisputed number one among the bulk supermarkets in French-speaking Switzerlandfor the last 30 years.Last fall, Dominique and Etienne Demaurex, sons and successors of Pierre Demaurexopened the third Aligro market in Sion. This store boasts a total floor space of12,500m2 of which 5,000m2 is sales floor. LKS KälteSchweiz AG/LKSFroidSuisse SA, a subsidiary of Carrier/Linde Refrigeration, was responsible forthe overall refrigeration and control technology in the normal area and deepfreeze area of the supermarket. Three compressor units were supplied, as well asdisplay cases with a total sales length of 180m and equipped the nine walk-in coldrooms with floor space of approximately 200m2. In addition, Carrier/LindeRefrigeration equipped the five deep freeze cells with floor space of approximately90m2.For normal cooling, the new CO2 composite cooling system CO2OLtec by LindeKältetechnik was used. Control and monitoring of the NC compressor units, whichalso work in the transcritical area, is handled by the newly-developed EckelmannVS3000C. All sales display case evaporators and cooling room evaporators areequipped with electronic expansion valves.The required overall cooling capacity for the normal cooling area is 322 kW. It isdivided into two separate integrated refrigeration units each with identical coolingcapacities. The deep-freeze area has a cooling capacity of 67kW. Its heat isdissipated in cascade operation by CO2 evaporating directly from the normal coolingsystems. In the sales areas as well, the direct expanding carbon dioxide ensures heatdissipation in the normal as well as in the deep-freeze area.A CO2 gas cooler in V-block design is used for transferring the heat (2 x 236kW) thatneeds to be dissipated to the ambient air.Cooling rooms with CO2 supercritical and deep-freeze rooms with CO2 subcritical.Equipped with Kuba CO2 evaporatorsIn the sales areas, customers can find fresh and frozen goods in a variety of differentcooled shelving, chill counters, islands and deepfreeze combinations from the LindeEvolution 5 series, as well as in a larger number of walk-in cold rooms and deepfreeze rooms. In these areas CO2 air coolers from Kuba are used exclusively.Heat recovery is utilised throughout. Thus, hot water for heating at 2 x150 kW isavailable during the heating season and hot service water at 90kW is available yearround.In the normal cooling system, the compressor unit system was divided into twopressure areas for the dimensioning of components. The high-pressure area wasconfigured at a maximum operating pressure of 115bar. This area includes the highpressure side of the compressors, the heat recovery system, the hot gas and liquid lineto the gas cooler, all refrigeration components on the high-pressure stage, as well as aspecial high-pressure valve.The maximum operating pressure for the other system components, for example thecollector or the liquid and suction line, is only 40bar. The evaporators in the normalcooling system are optimised on the refrigerant side for CO2 for technical flowreasons and configured for the higher pressure loads. Thus, for the greater part of thesystems, standardised commercial refrigeration components could be used that amongother things can also be used in CO2 deep freezing.Running costs are important when operating a refrigeration system and the refrigerantused is of crucial importance in this regard. If high outside temperatures are assumed,then R404A is said to show clear performance advantages over CO2.“However, if the favourable thermodynamic and technical thermal characteristics ofCO2 are taken into consideration, there is a different picture,” emphasises MarcusHöpfl, manager of the Buchser subsidiary and member of the management teamof LKS KälteSchweiz AG. He cites the following reasons:• Due to better heat transfer ensured by CO2, it is possible to operate equipment at anevaporation temperature that is 2K higher compared than R404A.• With CO2 being a high pressure refrigerant, there is a saturation temperature loss inthe suction line that is reduced by 1K compared to R404A, assisting oil return to thecondensers. The CO2 condensers in the normal cooling system can be operated withvacuum pressure, corresponding in total relative to R404A to a saturation temperaturethat is 3K higher.• The special characteristics of the transcritical process control and the good heattransfer characteristics of CO2 in the gas cooler enable cooling of the pressure gasclose to ambient.• At lower air temperatures a reduction of the condensing temperature toapproximately +10°C is possible when using CO2. The reason is that a sufficientlyhigh differential pressure exists relative to the evaporation pressure due to the higherpressure level of CO2 even at these low temperatures.• The current energy consumption of NC/DF DX CO2 systems is approximately15to 20% lower than comparable NC R404A systems with refrigerant/re-coolingsystem and DF DX. The energy data are based on measurements performed overa period of 12-18 months.• Current investment costs of NC/DF DX CO2 systems are equivalent to R404A,providing the NC system is more than 220kW or the surface area of the supermarketexceeds 2,500m2.For Marcus Höpfl, the results are clear: “CO2 should be looking at an exciting futureas refrigerant. Currently its implementation in refrigeration applications is somewhatmore expensive because the necessary components are not yet being produced in thesame quantities as are produced for systems that work with fluorinated refrigerants.Currently this acts as somewhat of a brake on demand. In the future, however, therewill not be a price difference even at lower system capacities.” 1CO2 Compressors for Light Commercial Refrigeration Ricardo A. Maciel(a); Marino Bassi(b) (a) EMBRACO – Empresa Brasileira de Compressores – Joinville/SC – BrazilTel.: +55 47 3441 2762 – e-mail: rmaciel@embraco.com.br(b) EMBRACO Europe srl – Riva Presso Chieri – ItalyTel.: +39 335 737 6085 – e-mail: marino.bassi@embraco.it1. ABSTRACTHFC refrigerant has been identified as a contributing factor with regard to global warming. This fact has put pressure onmost of the refrigeration industry to replace the HFC refrigerant fluids currently employed in vapor compressionsystems. In this search for an environmental friendly technology, Carbon Dioxide (CO2) has emerged as a leadingcandidate to be a replacement for HFCs. Today there is a strong focus on CO2 potential for beverage cooling applicationalthough it is still in the preliminarily stages. Moreover, in the design of compressors to run with high pressurerefrigerants like CO2 safety aspects must be a mandatory concern. When dealing with high pressure levels, compressorcomponents have their original design adapted to withstand such a high pressures, particularly acoustical mufflers,external shell, and compression mechanism. Regarding the external shell, the design approach goes beyond acousticaland aesthetics features as mostly observed in current refrigerating compressors. In order to safely enclose thecompression mechanism the application of a proper design methodology is mandatory to safeguard the structuralintegrity of both the compressor external shell and the whole refrigerating system. Looking for acceptable, cost-effectivesafety factors, a simultaneous design approach including advanced structural mechanics techniques, experimentation,safety standards revision, and Computer Aided Engineering (CAE) tools application is mandatory. The aim of this workis to present how Embraco has been approaching the structural design of its CO2 compressor to ensure safety andreliability. Also, a comparison between a CO2 compressor under development and a standard HFC compressor has beenperformed in both calorimeter and application tests. Preliminary data have showed that a CO2 can perform competitivelyto the HFC systems in the field.2. INTRODUCTION2.1. Brief CO2 history as refrigerant for cooling and heat pumping systemThe design of a refrigeration system involves many considerations. Design invariably requires a critical evaluation of thesolutions proposed by considering factors like economics, reliability, safety and environmental impact. The vaporcompression cycle has dominated the refrigeration market to date because of its advantages: high efficiency, low cost,and simple mechanical embodiments. Despite those advantages, one of the concerns regarding the use of these systemscomes from the fact that the refrigerating effect is produced by making a volatile fluid boil at a suitably low temperature.Most of the classes of volatile fluids currently in use aggress the ozone layer, promote the global warming of the Earthor present unfavorable properties to the human health and/or safety.In recent years environmental aspects are increasingly becoming an important issue in the design and development ofrefrigeration systems. In vapor compression systems, the banning of CFCs and HCFCs because of their negativeenvironmental impacts has made way for the HFCs refrigerants. Until now there has been no motive for the refrigerationmarket to find other alternatives. As environmental concern grows, alternative technologies which use either inert gasesor no fluid at all become attractive solutions with regard to the environmental issue.In this situation HFCs seem to be only an interim solution. Looking for final choices and taking into account regulationsfor greenhouse gas emissions, natural fluids become a promising alternative as refrigerant fluids. Some of theserefrigerants like the hydrocarbons and ammonia come with safety risks. If non-toxicity and non-flammability arerequired, the focus comes to CO2, which has been considered for low capacity applications operating in transcriticalrefrigeration cycle.2.2. Application of transcritical CO2 compressorsTranscritical cycle is that one in which the compressor discharge pressure is above the refrigerant critical point and thesuction pressure is below it. In other words, condensation does not take place at the high side heat exchanger and therefrigerant vapor and liquid phases co-exist in only one distinguishable phase. Figure 1 depicts a typical CO2transcritical cycle in a pressure-enthalpy diagram. Since usual ambient temperatures can exceed 31oC (CO2 critical2temperature), a CO2 refrigerating system will not exhibit condensation at the high side heat exchanger, as shown by theheat rejection process 2-3 in the figure, and temperatures and pressures will not be linked as in saturation (dome) region.In a refrigeration cycle where conditions range from subcritical to supercritical, CO2 reaches high pressures, as much as100 bars (10 MPa) or even more at high ambient temperature and/or extreme operating conditions. Below are depictedtypical pressure differences for design conditions employing common refrigerant fluids as well as CO2.Figure 1: (a) CO2 pressure-enthalpy diagram. (b) Pressure difference for common refrigerants and for CO2.2.3. Mainly safety and reliability issuesDespite the strong ecological appeal of CO2 refrigeration, the utilization of this compound as refrigerant fluid stilldemands solutions for some technical challenges, mainly the ones related to the high pressures associated to the CO2transcritical refrigeration cycle. The compressor structure must meet requirements anticipated by safety standardsincident in the refrigeration segment. Furthermore, taking into account the current version of those standards, therequirements for CO2 invariably will lead us to unfavorable design cost wise when comparing to the current refrigeratingcompressors design.Amongst compressor components affected by the replacement of high GWP refrigerant fluids by CO2, the external shellprobably is the one which deserves a particular attention. Since this component is developed to withstand the approvalload imposed by international codes like UL 984, and such a load is the result of a design pressure (refrigerant saturationpressure at 27oC) multiplied by a fixed constant (regardless the refrigerant fluid), one can easily reaches non-economicaldesign conditions. In the particular case of CO2 the hydrostatic approval pressure can exceed 350 bar while currentrefrigerants require 53 bar approval pressure by the same code. This requires special demands for construction material,geometry, tubing design and electrical connections development. In addition, once the shell represents a boundarybetween the refrigeration circuit and the surroundings, extreme care is to be taken in order to suit the mechanicalstrength to the design demands and with favorable safety factors weighted by safety and economics issues. 3. RELIABILITY AND SAFETY ASPECTS OF COMPRESSOR SHELL3.1. Standards EvaluationAiming to design a pressure vessel taking the advantage of some standard procedures or even good practices of than, agood approach in the design of such compressor would be make an effort to follow those specific standards for pressurevessels. Furthermore, following these standards in the very beginning of the development leads to a good assertivenessin getting results early in the development decreasing the try and failure approach time.However, some standards like the ASME code show a huge among of rules and recommendations that in most of thecases seems very conservative depending on the application. They are based on material selection, project development,manufacturing process, assembling and inspection. Unfortunately the “standard’ rules uses to avoid the applicability oreven refraining the application of the vessels in some temperatures, pressures imposing also geometric limitations likethe thickness of the shell or material selection.Since there are two different pressures level in a compressor shell for refrigeration, the discharge (high side) and suction(low side) should be design the resist these two different loads. Moreover, the experimental test should also be3performed concerning this aspect. In the IEC 60335-2-34, draft proposals for motor-compressors for R-744 intranscritical applications, the following pressures are specified for his kind of application, Table 1.Table 1 – Minimum low and high side test pressures.Pressure testNOTE 103 The values given above may not be high enough for some applications.In order to analyze how other standards is dealing with these issues, the ASME pressure vessels Section VII division IIhas been considered to figure out their concerns. Some concerned parts of this such standard have taken into account inthe following compressor development and its component design, like UG-19, UG-21, and UG 99. For details see [1].3.2. Material characterizationIn order to have a well understanding of all used materials in the CO2 compressor, mainly in the shell body, a deepanalysis of standards material have been performed. Concerning the possibility of having the shell in cast, both gray castiron and nodular cast iron have been evaluated. Due the notorious superior behave of the nodular comparing to the graycast iron, this first one has been chosen as the material for the cast vessel.For the cast iron specifications, the following ASME standard has been analyzed and token into account: ASME Boilerand Pressure Vessel Code, Section VIII, Division 1, Rules for Construction of Pressure Vessels, 2004 edition. A briefsummary of the standard concern is depicted in Table 2Table 2 – Material specification and its restriction according the ASME code.Elongation ASME Part code Restrictions Material18% Part UCD eas can be seen in the limitation of the standard and, and due to the special material treatment to reach thespecifications above, this lead us to developed our in-house approval test and material analysis regardless the soevidence advantage in follow the ASME or whatever standard for pressure vessels.Thus, aiming to evaluate a reasonable and cost effective material and make a trade-off analysis among feasibility andsecurity, the following approach has been considered in the material development:(a) Quality and homogeneously of the present material;(b) Weld joints evaluation in order to get all of their characteristics;(c) Mechanical properties of all current used material, including the main body material, weld joint material, andwelding properties;(d) Fatigue and fracture mechanics considering its fatigue _-N and _-N curves, KIC, J and so one;(e) Experimental and a complete laboratory program to evaluate all material and its component. Validation andexperimentation program;(f) A very well developed structural analysis by finite element, FEA. Where the Project by Analysis have been takeninto a big effort.40100200300400500Figure 2: Stress-Strain curve for raw cast iron, after thermal treatment and after welding.4. CO2 COMPRESSOR SAFETY AND RELIABILITY RESULTSA huge amount of numerical simulations and experimental tests have been performed in order to evaluate each proposeof the compressor shell aiming to a complete envelope analysis of its safety aspect: Collapse load, Plastic hinge, Threadanalysis, Weld analysis, Hydrostatic pressure test, and Fatigue test.4.1. Compressor shellThis component is surely the most important one concerning safety issue aspect and thus, is the subject of this paper. Itencloses al other compressor components guaranteeing their hermeticity and holding the CO2 inherent high pressure.Otherwise the cylinder head is facing the highest pressure within the enclosed shell, due the area and the volume thevessel shell shall be the weak point of the design. The external view of the entire compressor vessel is depicted in Figure3, where the shell and cylinder head is shown in cast body.The shell must be design taking into account a huge amount of structural and material safety issues, regarding materialbehave, plastic analysis, collapse load, fatigue properties, plastic hinge, thread evaluation, welding analysis and so one.Following pictures and analysis depicts these security issues aiming to characterizes and analyze the pressure vesselitself and their singularities like welding and thread.Figure 3: The CO2 compressor shell 3D model and the FEA result for total deformation due an elastic collapse load evaluation.4.2. Collapse loadA plastic analysis may be used to determine the collapse load for a given combination of loads on a given structure. Thefollowing criterion for determination of the collapse load shall be used. A load–deflection or load–strain curve is plottedwith load as the ordinate and deflection or strain as the abscissa. The angle that the linear part of the load– deflection or5load–strain curve makes with the ordinate is called _. A second straight line, hereafter called the collapse limit line, isdrawn through the origin so that it makes an angle _ = tan-1 (2 tan_) with the ordinate. The collapse load is the loadat the intersection of the load–deflection or load–strain curve and the collapse limit line. If this method is used, particularcare should be given to ensure that the strains or deflections that are used are indicative of the load carrying capacity ofthe structure.The result of collapse load can be figure out on Figure 3 where the total deformation is analyzed is the most criticalpoint. Figure 4 depicts two different proposes for the shell figuring out the pressure limit for both in a collapse load nonlinear simulation. The point where the straight line crosses the deformation line figures the collapse load pressureaccording to the ASME criteria.Figure 4: Collapse Plastic evaluation of two different proposes of compressor shell.4.3. Plastic hingeA plastic hinge is an idealized concept used in Limit Analysis. In a beam or a frame, a plastic hinge is formed at thepoint where the moment, shear, and axial force lie on the yield interaction surface. In plates and shells, a plastic hinge isformed where the generalized stresses lie on the yield surface.Depending on the region of the shell, the corresponding theory should be applied in order to evaluate their safetyfactory, meanly in discontinuity region.For that design pressure, each specific transition should be analyzed concerning its Tresca Stress and whether or not thepresence of plastic hinge. See Figure 5.Figure 5: 3D stress evaluation checking the presence of general plastic hinge formation.4.4. Thread analysisSome discontinuities such the thread region have a special treat of their stress and safety factor. The stress levelthroughout the filet section should not reach a specific value regarding its failure criteria, in this case, the fourth theoryof the elasticity and Tresca theory.6Pure Shear: The average primary shear stress across a section loaded under design conditions in pure shear (forexample, keys, shear rings, screw threads) shall be limited to 0.6Sy.Figure 6: Thread analysis regarding shear and intensity stress.4.5. Weld analysisIn the design of the weld joint in a such pressure vessels like CO2 compressor, special attention have been taken tofollow or at least figure out how the ASME code deal with this kind of joint. In the code is pretty clear how the involvedprocess is taking into account, like material selection, joint type, welding process, etc, according to the so called jointefficiency denomination.Joint efficiency is defined as the ratio of strength of a joint to the strength of the base metal, expressed in percentage.In the ASME code the section in which this issue is dealt is the Part UW, requirements for pressure Vessels Fabricatedby Welding. In this section, various type of joints, like but joint and lap joint are specified with their corresponding jointefficiency. Thus, one should use the corresponding strength ratio multiplier in the design of pressure vessel using thissuch kind of welding. See Table 3Table 3– Maximum allowable joint efficiencies for Arc and Gas welded joint, from ASME code Table UW-12.Joint Type Degree of Radiographic ExaminationButt joint 1.00 0.85 0.70Single full fillet lap jointwithout plug weldsNA1 NA 0.45In the ASME code there is also a characterization of the weld joint depending on its location on the pressure vessel, forinstance, whether it’s located at main shell body, communications chambers, nozzles, or transitions in diameterincluding joints between the transition and a cylinder at either the large or small end; circumferential welded jointsconnecting formed heads other than hemispherical to main shells, to transitions in diameter, to nozzles, or tocommunicating chambers. Depending on the location, special safety aspects is also a concern.However, in order to optimize the compressor shell development, the actual weld efficiency should be evaluated andexperimental tests take place aiming to reduce the conservativeness of this such code pursuance.4.6. Hydrostatic pressure testsFor each design proposes aiming to check the extreme pressure resistance of the shell, a hydrostatic pressure testperformed. This is a complete static strength test where all the shell components, that is, the main body material andweld joint are subject to the same pressure till its burning collapse. After the collapse test, the failure component isevaluated aiming to figure out its failure mode and the condition of their parts mainly cast and welding defects. Figure7depicts a failed compressor shell after an overload hydrostatic pressure test.1 Not applicable7Figure 7: A failed compressor shell after an extreme hydrostatic pressure test figuring out the maximum allowed vessel pressure.4.7. Fatigue testsAiming to evaluate the fatigue performance of the compressor itself and also different configurations for material,welding and so one, fatigue tests have been performed in special specimen samples and in the pressure vessel.The fatigue test in the specimens has followed standardized sample tests (ASTM E399/90) and it has been cut fromwelded cast iron plates.The fatigue limits have been evaluated in different places (melted zone, heat affected zone and base metal) with specialindentation on the samples. The picture of a specimen cut from the main body of the welded shell can be seen on Figure8(b). In these pictures the specimen is subjected to fatigue load in the universal axial tension machine.(a) (b)Figure 8: (a) A fatigue test of the compressor shell running on a special developed machined (b) specimen sample cutfrom the welded main body of the compressor shell and a fatigue test running on a uniaxial universal tension machineFor the fatigue test of the final compressor shell, both high and low side of the enclosed vessel part have been submittedto pressure load according working condition for each compressor side. As a first approach to perform a fatigue test andalso to have a reasonable result in safety life, the tests have been performed according Table 1. However, even the IECcode says that those pressures could not be enough and those ones could differ depending upon the compressorapplication. Thus, some other reasonable pressure level fatigue test should take part of the shell development and thistopic is still a mandatory concern in the CO2 compressor development.A fatigue life testing running in the high pressure side of the compressor shell can be seen on Figure 8, where few shellsare submitted to a variable pressure cycle according Table 1. This is a special Embraco in house development machinedesigned concerning safety aspects for the operator. The pressure cycle loop is monitoring by software and the numberof cycles and pressure conditions data is registered.The notorious advantage of submitting the whole shell to fatigue load test is the evaluation of all vessel issues, likewelding, materials, threads, and all other possible weak points of the shell design, guaranteeing the safety factor at all.84.8. Cylinder head analysisThe same approach should be applied in the design of the cylinder head. Moreover, this component could be alsoconsidered a critical weak point since it faces the highest pressure level and also the temperature gradient. So in thecalculation of the safety factor, the stress to be considered should be that one given by the discharge pressure load plusthat one resulted by the temperature gradient.Another important weak point that should be a concern is the discontinuity resulted by the connectors. This region couldface a high stress level due the concentration factor given by the presence of a hole in a so high pressure stress region.See Figure 9.Figure 9: The stress level on a cylinder head component. Special attention should be taken in discontinuities like shape transitionsand tube holes.5. METHODOLOGY AND COMPARISON BASIS FOR PERFORMANCE TESTSSince January 2004 Embraco has been researching and developing CO2 compressors. Based on the demands required byCO2 as a refrigerant fluid, a completely new compressor platform was developed. Many CO2 compressor samples havebeen tested to date in order to assess the performance of the concept.All the results obtained in this work were compared to current HFC technology in the field. Neither the improvement oncurrent HFC refrigeration compressors nor the improvement on the appliance were considered despite the opportunitiesfor that. CO2 is applied as a drop-in, keeping the refrigeration system technology at the same level it is today. Regardingcalorimeter tests, the comparison basis is the volumetric and the compressor external isentropic efficiencies while theenergy consumption in a monthly basis constitutes the comparison parameter for the appliance tests.5.1. CO2 compressor testing program and resultsThe facilities for the CO2 compressors performance evaluation were based in a hot cycle calorimeter in which the testingprocedure consists of imposing the pressure and temperature at the compressor inlet. The discharge pressure and theambient temperature are also imposed and the parameters measured are the refrigerant mass flow rate and thecompressor power consumption. Figure 10 depicts an outline of the test rig for CO2 compressor evaluation.9Figure 10: Test rig for CO2 compressors performance evaluation.Calorimeter tests were performed at different evaporating temperatures and discharge pressures for the CO2compressors. Evaporating temperature was varied from –5oC to –15oC while the discharge pressure ranged from 83 barto 95 bar. Ambient temperature was kept constant and at 32oC. The compressor inlet temperature was also kept constantand equal to the ambient temperature.Figures 11, 12, and 13 show the performance curves for the CO2 compressor, namely cooling capacity, isentropicefficiency, and volumetric efficiency. In the same plot the respective curves for an standard HFC compressor can beseen. For the CO2 runs, the cooling capacity was calculated considering an approach of 4.6K in the gas cooling process.For the HFC curve, the condensing temperature considered was 43oC and the sub-cooling as 0.4K. The isentropic andvolumetric efficiencies were calculated as described in the appendix of this work.Figure 13: CO2 compressor volumetric efficiency map.5.2. Appliances testing program and resultsThe compressor performance comparison presented in section 5.1 is very useful to understand the improvementsexpected on compressor performance when moving from the HFC-134a to CO2.However, when comparing only compressor performance in a calorimeter test some variables are not contemplated, andsome assumptions such as the approach temperature at the gas cooler outlet for the CO2 cycle or the subcooling degreeat the condenser outlet for the HFC cycle, and isenthalpic expansion process, have to be made.Therefore, an additional comparison between CO2 and HFC-134a technologies was proposed based on a finalapplication. A 405 cans storage capacity beverage vendor cabinet was chosen for that purpose. The tests were performed11at 32°C ambient temperature and 65% relative humidity for both HFC-134a and CO2. The overall system energyconsumption was measured and the contributions of the compressor and other system components (fans, lights,electronic controls) were evaluated apart. Figure 14 shows the energy consumption results for the baseline system withHFC-134a as well as with CO2.The standard evaluation and analysis is surely an excellent and mandatory approach in the design of a such kind ofCompressor. It takes the advantage of a huge experience on the development of pressure vessels, if we considered theSME for instance, but also the intrinsic experiences of each specific standard committee. Moreover, following somegood practices of those standards leads a development to be more assertive in the very beginning of the design, likematerial selection, process chosen, manufacturing issues and so on.However, the general approach of the standard leads also to a much high conservative approach in components designand safety criteria. This approach tends to not achieve an optimized design concerning material selection optimization,thickness and strength of all components and failure mode criteria resulting in a safety factor normally pretty high.Thus, an efficient way to design a such compressor would be that one where all involved issues are very well understoodand deeply analyzed. For example, instead of chose a material exactly according to the specification of the standard,what can lead to a high cost than another cheaper one, one can figure out the actual strength of the componentthroughout advanced FEA analysis and experimental verification. This approach is some call Design by Analysis insteadof that one Design by Rules.The Finite Element Analysis allows the design engineering to have a deep understanding of the component behave andto achieve a better design where each part of the structure are optimized for the such working condition. This leads to areasonable safety factor which is not so small to be hazardous but not so high than makes the compressor projectunfeasible regarding economic point of view.This Design by Analysis approach in compressor and its components development has depicted a very important pointfor discussion: the required updating of some current standards for household and light commercial compressors forrefrigerating. Mainly those one developed based upon CFC refrigerants operating in much less working pressure thanCO2.Results for isentropic and volumetric efficiency were shown for a CO2 compressor prototype and for an standard HFCcompressor currently in the field. It was found that CO2 compressor prototype can deliver better isentropic efficiencythan an HFC compressor, regardless the discharge pressure and the evaporating temperature within the ranges tested.The same conclusion could be observed for the volumetric efficiency. The gains observed with the CO2 compressorprototype varied from 45% to 50% in terms of isentropic efficiency, and from 32% to 44% in terms of volumetricefficiency. Superior compression and volumetric efficiencies can make the CO2 application feasible, overcoming theintrinsically low CO2 transcritical cycle efficiency.12Energy consumption test results performed at 32oC ambient temperature and 65% relative humidity were disclosed. Theoverall energy consumption of the HFC system was reduced by 10% when the HFC compressor was replaced by a CO2prototype and the capillary tube adjusted for the new fluid. Considering only the compressor energy consumption, thatis, not accounting for condenser and evaporator fans, lights, and electronic controls, the reduction observed was 11.8%.7. REFERENCES[01] ASME, The ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, ASME, New York, NY, USA,2005.[02] ASME, The ASME Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NB, ASME, New York,NY, USA, 2005.[03] Pissarenko, G. S., Iakovlev, A. P., Matveiev, V. V., Prontuário de Resistência de Materiais, Editora Mir Moscou,Tradução para o Português, 1975[04] O’Brien, R. l. (ed.), Jefferson’s Welding Encyclopedia, 18th Edition, American Welding Society, 1997.[05] ASME, Criteria of Section III of the ASME Boiler and Pressure Vessel Code for Nuclear Vessels[06] Mackenzie, D. & Boyle, J., Pressure Vessel Design by Analysis, A Short Course, ABCM, 1996[07] Gerdeen, J. C., A Critical Evaluation of Plastic Behavior Data and a United Definition of Plastic Loads For PressureComponents, Welding Research Council Bulletin # 254, Nov. 1979[08] REFRIGERANTS, NATURALLY. (2004) Companies, NGO´s and international organizations join forces to fightclimate change. Retrieved March 03, 2005, from http://www.refrigerantsnaturally.com/doc/Press%20Release.pdf

Refrigerant Monitoring and Reporting Includes Carbon (CO2) Emissions and Greenhouse Gas Management

Daniel J. Stouffer

February 26, 2009

In many countries, carbon emissions are required by law to be reported across an organization's entire footprint; hence the coined term "Carbon Footprint. Carbon data and detailed records of energy, fuel, and refrigerant gas consumption fall under regulatory compliance rules and must be reported in paper, and increasingly, electronic format - Globally.

Refrigerant systems use high levels of greenhouse gases, so the EPA established the Climate Registry Protocol for calculating carbon emissions on a regular basis. The international equivalent of this requirement is outlined in the Montreal Protocol and Kyoto Protocol. The main purpose for calculating carbon emissions is to begin reducing the damaging effects that refrigerant gas has on the environment.

Commercial refrigeration and air-conditioning (RAC) systems or heating, ventilation and air conditioning (HVAC) systems operate on refrigerant gas, which is made up of hydrochlorofluorocarbons (HCFCs), chlorofluorocarbons (CFCs) and perfluorocarbons (PFCs). When broken down, these substances contain carbon, chlorine, fluorine and hydrogen.

These gases are major ozone depleting substances. By calculating carbon emissions, government environmental agencies will be able to better understand the situation. Companies who fail to report their carbon emissions will be issued a substantial fine.

Various carbon emissions reporting protocols have emerged from the EPA, ISO, World Resource Institute, and Climate Registry protocols. All of these documents define in great detail how organizations must collect data, calculate carbon emissions, and report the results. In summary, the mandatory regulations require facilities using refrigeration and air-conditioning (RAC) systems or heating, ventilation and air conditioning (HVAC) systems to collect, organize, calculate and report carbon emissions.

Unfortunately, all HVAC-R systems will vent refrigerant gases from time to time; all of which leads to ozone depletion and increased carbon emissions for the emitting organization. Trying to determine how much carbon is emitted is an intricate process. Conducting a carbon audit or a carbon footprint across an organization begins with collecting data related to each location, the assets being used, and identifying high global warming potential gases. From there, a determination on how much of each gas is released must be made. Then various reports that include tracking methods need to be completed and submitted.Refrigerant management programs can best handle the tedious process of calculating carbon emissions. Across a distributed organization or one with more than a couple of locations and a few HVAC-R systems, a web-based or database driven refrigerant management solution is more effective and less prone to error as are paper log books. A refrigerant management program that includes a solution for refrigerant gas tracking and an automated way to calculate carbon emissions is important. Solutions like this make is easier to handle calculating carbon emissions for all AC/HVAC systems operated by a company.

There are several reasons that led to the EPA and international environmental agencies to require companies to include calculating carbon emissions in their reports. It is an important step to define your organizational boundaries, where you do business, and to identify the refrigerants you own or other sources of greenhouse gases (GHGs). Equally important is to establish a tracking mechanism for determining how much harmful gases are released at any given time. The information and data collected for the emerging refrigerant management programs will enhance and improve atmospheric conditions with specific requirements for reducing carbon (CO2) emissions.

By calculating carbon emissions, companies will be able to recognize the extent of their carbon footprint. For companies with multiple locations using refrigeration and air-conditioning (RAC) systems or heating, ventilation and air conditioning (HVAC) systems, the task becomes even more critical.

But there is help to address this challenging issue. Emerging software provided by clean-tech development firms track carbon dioxide gas emissions across all sites so companies can do their part to ensure a healthy environment for years to come.

Daniel Stouffer, Product Manager at Verisae, has much more detail on the importance of carbon emission management, tracking, and reporting. Refrigerant Tracker makes it easy to monitor, manage, and report refrigerant gas usage across multiple locations.

CO₂ Hydrates in Refrigeration Processes

Laurence Fournaison, Anthony Delahaye,* and Imen Chatti Global warming concerns have led the refrigeration industry to seek and develop new refrigeration systems with a reduced impact on the environment. The use of two-phase secondary refrigerants generated by a primary closed refrigeration circuit is a promising solution. Solid−fluid secondary refrigerants are known for their higher energy efficiency compared to single-phase fluids, because of the additional latent heat of the solid phase. The objective of the present work is to investigate experimentally the latent heat of CO₂ hydrate−ice mixture systems in comparison to that of ice slurry systems. By using a new DTA apparatus, the CO₂ hydrate−ice mixture was shown to offer a dissociation enthalpy of 507 kJ/kg that is higher than that of ice (333 kJ/kg). Artificial tuned CO₂ hydrate−fluid systems appear to be an environment-friendly alternative for refrigeration and air-conditioning systems that can be used in a wide range of applications. In three previous articles, we have presented an overview of CO2 (R-744) as a refrigerant, its applications in industrial refrigeration, and a case study of a CO2 cascade system in a European supermarket. (See “CO2 in Refrigeration Applications,” Oct. 6, 2003; “CO2 in Industrial Refrigeration,” Nov. 3, 2003; and “CO2 is Keeping Supermarkets Cool,” Dec. 8, 2003.) The systems presented were all subcritical — that is, the refrigeration cycles were entirely below the critical point of CO2. Now, after a brief review of CO2 characteristics, comparing subcritical and transcritical cycles, we will present a functioning transcritical system with a hermetic CO2 compressor and discuss design considerations. CO2 is a component of our atmosphere that is essential to life. It has no ozone depletion potential and insignificant global warming potential, so CO2 has no regulatory liability, as do HFCs. There is no need to account for the amount used, and it does not need to be reclaimed. (Characteristics of CO2, compared with those of R-134a and R-404A, are shown in Table 1.) benefits of CO2 are that it is a natural substance, it is cheap, readily available, not poisonous in any common concentration, and nonflammable. At prices a bit over $1 per pound, it is truly an inexpensive refrigerant. The grade used must be dry, but it can presently be obtained in 99.9-percent purity from companies that supply welding gases, with a 20-pound tank selling for about $21.

Refrigeration Applications

CO2 is not new to refrigeration. Its use began in the mid-nineteenth century and steadily increased, reaching a peak in the 1920s. Its use declined with the introduction of chlorofluorocarbons (CFCs) that operated at much lower pressures. Use of CO2 continued, but chiefly in cascade systems for industrial and process applications. Recently, strong interest has been shown in CO2 as a refrigerant by vending machine manufacturers. There are also possibilities for other light commercial refrigeration applications, as well as for residential air conditioning.

The major challenges in CO2 refrigeration involve the relatively high working pressures. The supercritical portion of the transcritical cycle takes place above 1,067 psia. The phase diagram for CO2 is shown in Figure 1. L’industrie automobile a fait un pas important lorsque les systèmes de climatisation des véhicules commercialises dans de nombreux pays sont passes d’un fluide frigorigène a chlorofluorocarbones ( CFC-12) aux hydrofluorocarbures (HFC-134a) moins nocifs pour la couche d’ozone. Cependant, au regard des objectifs fixes par le protocole de Kyoto et la marginalisation des systèmes de climatisation embarques, le remplacement du HFC-134a peut représenter un enjeu important pour réduire les émissions de gaz a effets de serre : En effet, le HFC-134a a un impact 1300 fois plus important sur le réchauffement de la planète que le CO2 a quantité égale en poids. Le fonctionnement d’un climatiseur joue sur la compression d’un gaz et de sa détente. Un compresseur comprime le gaz chaud a très haute pression qui passe dans un condensateur et dans un échangeur thermique interne (qui permet des échanges thermiques avec la zone basse pression) pour être refroidi puis passe dans le détendeur. Il en sort un liquide qui permet le refroidissement de l’habitacle en passant dans l’évaporateur. Le gaz a basse pression est ensuite accumule dans un condensateur avant de circuler dans l’échangeur thermique et de repartir dans le compresseur pour un nouveau cycle. Le CO2 est un gaz envisageable comme réfrigérant des systèmes de climatisation en remplacement des HFC-134a dans un futur proche. L’emploi du CO2 relève plusieurs difficultés liées a la pression a laquelle il doit être employé pour être utilise comme fluide réfrigérant. En effet, la température critique du CO2 est plus basse que celle du HFC-134 et sa pression critique est plus élevée ce qui oblige le système de climatisation a fonctionner dans des conditions plus difficiles a réaliser. Cela implique des matériaux plus résistants , donc plus lourd et plus couteux, ce qui freine la commercialisation de ce type de système a l’heure actuelle. Toutefois, Dense, un équipementier Japonais, a équipé en 2002 le véhicule expérimental de Toyota a pile a combustible d’un système de climatisation a CO2. Le climatiseur peut fonctionner pour réchauffer l’habitacle, ce qui est un facteur non négligeable si on envisage le développement dans le futur de véhicules a pile a combustible qui ne disposent pas de source chaude (moteur thermique) pour servir de chauffage.

Rédacteur : Etienne Joly, Service pour la Science et la Technologie Ambassade de France au Japon transport@ambafrance-jp.org 359/MECA/1577

En Suisse, la Haute École d'Ingénierie d'Yverdon a inventé un nouveau système de réfrigérateur qui consomme moins d'électricité et qui ne pollue pas. «Tout le froid dont nous avons besoin est produit à partir d'électricité et cela représente 15 à 20% de la consommation nationale» estime Fabrice Rognon de l'office fédéral de l'énergie, qui finance une partie des recherches. Ce réfrigérateur est plus précisément magnétique. Il ne contient aucun gaz nocif pour l'environnement et consomme deux fois moins d'électricité. L'air est refroidi grâce à un matériau spécial qui change de température quand il est en contact avec un aimant. Preuve de l'efficacité du système : La Haute Ecole d'Ingénierie d'Yverdon vient de signer avec un gros fabricant d'électroménager ! On a étudié deux concepts de meubles de vente de supermarché, à groupe incorporé et utilisant du CO₂. Dans le premier concept, les unités de refroidissement placées dans chaque meuble rejettent de la chaleur vers un circuit de récupérateur de chaleur. En utilisant un procédé transcritique avec du CO₂, il est possible d'obtenir un glissement de température très large dans le circuit, notamment de 50-60 K, et un débit masse correspondant de faible volume. La chaleur perdue de température élevée (70-75 K) est disponible pour le chauffage ou l'alimentation en eau chaude. Le surplus de chaleur est rejeté dans l'air ambiant par un échange de chaleur direct et, si nécessaire, par l'utilisation d'un refroidisseur d'appoint. On a effectué des simulations pour un supermarché de taille moyenne. On a comparé un système au CO₂ avec un système à détente directe utilisant du R22, et notamment la consommation énergétique totale du supermarché, pendant un an, sous un climat type du sud de l'Europe. Il s'est avéré que le système utilisant du CO₂ a permis de réduire la consommation énergétique totale de 31 %, par rapport au système au R22, chauffage de l'espace et de l'eau inclus. Dans le deuxième concept, les unités au CO₂ ont été équipées d'un condenseur prévu pour rejeter la chaleur directement aux endroits où circulent les clients du supermarché, lorsqu'un chauffage est nécessaire. Durant les mois d'été, on utilise un circuit de récupération de la chaleur perdue qui permet d'extraire la chaleur. Si l'on ne considère que la consommation électrique, la demande en électricité du système au CO₂ a été réduite au même niveau que celle du système au R22. On a conçu deux meubles de vente dans le but d'évaluer la performance et les conditions de fonctionnement. L'expérience du fonctionnement a été très prometteuse. L'efficacité est certes inférieure de 10-15 % aux prévisions, mais, si l'on considère que des améliorations vont être apportées à tous les composants, l'efficacité visée pourra être atteinte. Les efforts doivent se porter sur le compresseur, qui, pour lors, est une première version d'un compresseur semi-hermétique utilisant du CO₂.

Source / Source

Congrès
Natural working fluids '98 IIR - Gustav Lorentzen conference : ( Oslo, 2-5 June 1998 ) = Fluides actifs naturels conference IIF - Gustav Lorentzen
Institut international du froid. Commission B2, B1, E1 & E2. Conférence, Oslo , NORVEGE (02/06/1998)
1998 , n^o 4, pp. 270-280[Note(s) : [766 p.]] (bibl.: dissem.) ISBN 2-903633-97-5 ; Illustration : Illustration ;

Coop veut parvenir à un bilan CO2 neutre d'ici 2023. Pour atteindre cet objectif, l'entreprise prévoit, entre autres, d'abandonner les combustibles fossiles, d'utiliser systématiquement les rejets thermiques, d'améliorer l'isolation et de mettre ses filiales en conformité avec le standard Minergie. La plus grande entreprise suisse de commerce de détail sera aidée dans son projet par Alpiq InTec. Le département Installations frigorifiques à Interlaken a réalisé au printemps 2009 la première installation frigorifique booster transcritique.

Chez Coop, les points non étanches des installations frigorifiques utilisant des réfrigérants synthétiques laissent échapper dans l'atmosphère quelque 30 000 kg de CO2 par an. Malgré tous les efforts déployés, notamment des travaux de maintenance préventifs, les fuites de réfrigérant n'ont pas pu être totalement éliminées. Coop a donc décidé de bannir de ses installations frigorifiques ces produits dangereux pour le climat. La solution: utiliser des systèmes respectueux de l'environnement, qui fonctionnent avec du gaz carbonique et ne rejettent que 30 kg de CO2 par an. Ils présentent de surcroît un effet secondaire positif: grâce à l'installation des nouveaux systèmes, Coop pourra économiser plus de 100 000 kWh d'électricité par an, ce qui correspond à la consommation annuelle (5000 kWh) de 20 ménages helvétiques.

Pas de pollution de l'atmosphère
Il y a deux mois, Coop a ouvert à Kerzers, dans le canton de Fribourg, un supermarché équipé du premier système à booster CO2. Il s'agit d'une installation multiplex à deux étages de pression, qui peut alimenter en froid chaque poste réfrigéré à la température requise. L'installation frigorifique fonctionne avec du gaz carbonique (CO2) comme réfrigérant. Elle a été conçue par Frigo-Consulting AG de Gümligen-Berne et installée par le département Installations frigorifiques d'Alpiq InTec West AG, à Interlaken. Le système à booster CO2 alimente en froid tous les postes réfrigérés et de congélation, soit 90 mètres linéaires de meubles ainsi que des salles, les températures allant de plus cinq degrés à moins vingt degrés Celsius. Dans les installations frigorifiques, le CO2 – un réfrigérant naturel – circule en circuit fermé et fournit, si nécessaire, de l'énergie pour le chauffage et la production d'eau chaude. Le CO2 étant prélevé dans l'atmosphère, il n'a pas d'effet polluant quand il est rejeté.

«Plus sophistiquée que les installations à réfrigérant synthétique»
Pour mener à bien la conception et la réalisation de cette installation respectueuse de l'environnement, un véritable partenariat entre le maître d'ouvrage, à savoir Coop Région Berne, le bureau d'ingénieurs Frigo-Consulting AG ainsi que le département Installations frigorifiques d'Alpiq InTec West AG était nécessaire. «L'utilisation du CO2 comme réfrigérant a exigé de tous les participants qu'ils modifient leur façon de penser. Les processus, de la conception à la maintenance en passant par le montage, sont en effet plus sophistiqués que ceux des installations utilisant des réfrigérants synthétiques, car les pressions sont plus élevées. Cela a représenté un véritable défi pour l'équipe», a déclaré rétrospectivement Kurt Goetz d'Alpiq InTec West AG.

Coca-Cola, la firme d'Atlanta mondialement connue, a promis de réduire ses empreintes de carbone par l'achat de 100 000 distributeurs de boisson fonctionnant au dioxyde de carbone !

En effet, la plupart des distributeurs automatiques (boissons, alimentations, confiseries etc.) participent au réchauffement planétaire en employant des systèmes de réfrigération qui utilisent des hydrofluorocarbones (HFC) - un sous-produit industriel - contenant des produits chimiques tels que le méthane et l'éthane.

Il s'avère que l'utilisation du dioxyde de carbone pour la réfrigération en lieu et place du HFC est environ 1 000 fois moins nocifs pour l'environnement. C'est pourquoi, le géant de la boisson qui gère aujourd'hui un parc de 10 millions de machines dans le monde a décidé d'en renouveler une partie avec un système réfrigérant au CO2.

Le responsable de Coca "Neville Isdell" a indiqué que ces nouvelles machines avaient un coût supérieur de 25 % aux systèmes HFC classiques.

Coca-cola a par ailleurs investi 40 millions de dollars dans la recherche technologique des prochaines générations de réfrigération.

1) POURQUOI le CO2- Protocol de Kyoto- GWP (Global Warming Potential)- TEWI (Total Equivalent Warming Impact) 2) PROPRIETE DES REFRIGERANT (CO2, HCFC-22, HFC-134 HFC-507, NH₃)- Application et Avantage de chaque réfrigérant - Spécifications du CO2 pour application de réfrigération 3) CYCLE DE RÉFRIGÉRATION au CO2- Cycle sub-critical- Cycle transcritical- Efficacité théorique de chaque cycle comparé avec HCFC-22, HFC-134 HFC-507 4) AUGMENTATION DE L’EFFICACITÉ ENERGETIQUE- Échangeur de chaleur liquide-succion- Éjecteur- Expandeur- Opération a basse température extérieur 5) APPLICATION DES CODES AU CO2- ASHRAE- UL- B51 / B52 6) SYSTEME EN RECIRCULATION 7) SYSTEME A EXPANSION DIRECT 8) EVAPORATEUR - Manufacturier disponible d’évaporateur- Caractéristiques 9) « REFROIDISSEUR DE FLUIDE » et CONDENSEUR- Caractéristique avantage et fonctionnement de chaque type (air, eau) 10) COMPRESSEUR DISPONIBLE- Type de compresseur applicable au CO2- Sub-criticalo Plage d’opération- Transcriticalo Plage d’opération 11) UNITÉ-COMPRESSEUR- Cascade- Transcritical 12) HUILE DU COMPRESSEUR ET CO2- Caracteristique 13) COMPOSANTES - Séparateur d’huile, accumulateur de succion, échangeur de chaleur liquide-succion- Description des Systèmes et Application requérant leur utilisation. - TXV 14) TUYAUTERIE DE REFRIGERATION- Critères du choix du type de matériaux- Détermination de la pression de ruptureo Formule de Barlowo Équation de Boardmano Équation de Lame- Détermination du dimensionnement- Perte de pression et vitesse permise 15) PROTECTION CONTRE LA SURPRESSION 16) DEGIVRAGE - Description des différents types- Limitations des différents type 17) DIMENSIONNEMENT DES ACCUMULATEURS (système industrielle)- Accumulateur horizontal- Accumulateur vertical 18) POMPE de RECIRCULATION (système industrielle)- Manufacturier disponible- Caractéristiques 19) LISTE D’INSTALLATION AU CO2 20) APPLICATION – SUPERMARCHE- Caractéristique particulière- Avantages – Désavantages 21) APPLICATION - INDUSTRIEL- Caractéristique particulière- Avantages – Désavantages 22) APPLICACION - UNITE AUTONOME (Chauffe eau – chauffe piscine – armoire réfrigéré)- Caractéristique particulière- Avantages – Désavantages Les épiceries pourraient émettre 3900 fois moins de GES

Le Groupe CSC pourrait bien révolutionner le secteur de l'alimentation canadien en implantant un système de réfrigération qui permettrait aux épiceries d'émettre 3900 fois moins de gaz à effet de serre.Il y a près d'une semaine, le Groupe CSC annonçait l'implantation d'un système réfrigération dans une épicerie IGA de Cap-Rouge. L'entreprise soutenait alors pouvoir réduire considérablement la quantité d'émission de gaz à effet de serre (GES). Et la solution envisagée semble pour le moins simple : substituer le CO2 aux gaz synthétiques qui servent normalement de réfrigérants. Ceux-ci émettent 3900 fois plus de GES que le dioxyde de carbone.Pour une épicerie de superficie moyenne - 40 000 pieds carrés -cela représente une réduction d'environ 900 tonnes en émission de GES, « soit la quasi-totalité des émissions qu'elle génère», indique Luc Simard, ingénieur responsable du projet. Le Groupe CSC a baptisé ce système, l'Eco2-System. Ce dernier comporte également un procédé de récupération de la chaleur qui permet de chauffer 100% de l'établissement. Si un tel système était appliqué à l'ensemble des quelque 6000 magasins d'alimentation canadiens, il serait possible d'abaisser la quantité d'émissions à un niveau équivalant au retrait de plus de deux millions d'automobiles sur les routes du pays. Deux millions de voitures! « Un pas considérable pour l'atteinte d'objectifs de réduction. Et ce n'est que le début, car le procédé peut être appliqué », lance Luc Simard. Et les avantages ne sont pas qu'environnementaux, car le système de réfrigération pourrait réduire jusqu'à 10% de la facture énergétique d'un établissement, estime Luc Simard. «Aussi, le CO2 est huit à 10 fois moins cher que les gaz synthétiques. Contrairement à ces derniers, les entreprises ne peuvent pas breveter le dioxyde de carbone», indique-t-il.Alors, pourquoi ne pas avoir adopté plus tôt un tel système? En fait, les premiers systèmes de réfrigération utilisaient le dioxyde de carbone. Ce n'est qu'à partir des années 1920 et 1930 que le CO2 fut graduellement abandonné. «À l'époque, le CO2 posait de nombreux défis techniques. Et parallèlement, des entreprises ont découvert des molécules synthétiques qui semblaient idéales jusqu'à ce qu'on découvre, dans les années 70, les effets négatifs qu'ils avaient sur la couche d'ozone ».À partir des années 90, on a recommencé à utiliser le CO2 utilisé en tant que réfrigérant. Toutefois, en Amérique, le système de l'entreprise québécoise CSC est une première. Et le secteur est prometteur. Pour preuve, outre le IGA de Cap-Rouge, quatre autres projets similaires ont vu le jour ou verront sous peu le jour : un Métro et trois autres IGA.

Changements climatiques, Initiatives d'entreprises, Science et recherche, À la une...

Réduire ses émissions de GES de 3900 fois ? Un IGA l’a fait !

26 novembre 2009

Le Groupe CSC implante chez IGA DES SOURCES à CAP-ROUGE son système de réfrigération écologique unique au monde. Les émissions de GES du tout nouveau Eco2-System sont de 3900 fois inférieures à celles des technologies actuelles sur le marché.

Le propriétaire du supermarché IGA des Sources Cap-Rouge, M. Alain Gagné, ainsi que le président du Groupe CSC, M. Serge Dubé, ont inauguré le 18 novembre dernier le tout nouveau supermarché IGA des Sources Cap-Rouge, doté du système de réfrigération écologique, l’Eco2-System. Unique au monde, le système développé par le Groupe CSC utilise le CO2 en tant que réfrigérant et permet une forte réduction des émissions de gaz à effet de serre jusqu’à 3900 fois inférieures aux émissions des technologies actuelles sur le marché.

L’immense établissement, d’une superficie de 42 800 pieds carrés construit au coût de quinze millions de dollars présente un concept hautement innovateur, grâce entre autres à de toutes nouvelles configurations des rangées d’épicerie permettant une circulation facilitée du client.

M. Gagné ne cachait pas son enthousiasme, « nous voulions construire une épicerie au concept révolutionnaire. Une telle vision impliquait nécessairement de nouvelles approches à tous les niveaux du projet, que ce soit la configuration des rangées, le choix des matériaux ou le design des lieux. Toutefois, l’impact de nos activités sur l’environnement revêtait une importance capitale. Nous sommes donc très fiers d’offrir à nos clients un système de réfrigération totalement non polluant ».

Les équipes de Messieurs Dubé et Gagné ont compté sur SD Réfrigération pour assurer l’installation de l’Eco2-System au IGA des Sources à Cap-Rouge. L’entreprise, partenaire d’affaires du Groupe CSC pour la région de Québec, possède les compétences techniques ainsi que le réseau nécessaires pour assurer la vente et l’implantation de ce système unique fonctionnant au CO2 dans les supermarchés et autres établissements commerciaux.

Écologique et meilleure efficacité énergétique

Le nouveau système développé par le Groupe CSC utilise le CO2, un gaz qu’on associe généralement au réchauffement de la planète, mais qui devient par l’entremise de la technologie innovatrice de la Société, un véritable ami de l’environnement en permettant une réduction marquée des GES. En effet, le CO2 utilisé en tant que réfrigérant a un impact sur le réchauffement climatique très inférieur aux réfrigérants synthétiques. De plus, un système de réfrigération utilisant le dioxyde de carbone contient une moins grande quantité de réfrigérant en raison de sa capacité volumétrique qui est de 6 à 8 fois supérieure à celle des réfrigérants synthétiques tout en assurant une conservation et une fraîcheur optimale des aliments.

L’équivalent de deux millions d’automobiles de moins sur nos routes

Par ailleurs, l’Eco2-System comporte un procédé de récupération de la chaleur permettant aux détaillants en alimentation d’éliminer le besoin de recourir à un système de chauffage conventionnel pour tout leur établissement. De ce fait, si les 6500 détaillants en alimentation existant au Canada qui utilisent des systèmes de réfrigération conventionnels, responsables d’importantes émissions de gaz à effet de serre, remplaçaient ces systèmes par l’Eco2-System, nous pourrions observer une baisse des quantités d’émissions équivalant au retrait de plus de deux millions d’automobiles sur nos routes.

À propos du Groupe CSC

Fondée en 1982, le Groupe CSC est une entreprise spécialisée dans le développement de systèmes de réfrigération destinés aux détaillants en alimentation ainsi qu’au secteur industriel. Au fil des années, l’entreprise a mis au point différents systèmes pour répondre aux besoins variés de ses clients, en s’appuyant sur sa plateforme technologique brevetée SMARTREFMC. Dans le domaine de l’alimentation, la Société s’est positionnée comme un leader en Amérique du Nord, grâce à sa grande capacité d’innovation ainsi que par la qualité, la performance et la fiabilité de ses produits. Basée à Les Côteaux, la Société compte, par l’entremise de ses différentes unités affiliées, quelque 130 employés.

NEW HEAT RECOVERY AND DEFROST METHODS FOR SUPERMARKETMULTIPLEX REFRIGERATION SYSTEMSVASILE MINEALTEE (Hydro-Quebec), Shawinigan, CanadaSERGE DUBÉRSD Réfrigération Inc., Vaudreuil - Dorion (Québec), CanadaJORDAN KANTCHEVSystèmes LMP Inc., Laval (Québec), CanadaSummaryTwo high-efficiency multiplex supermarket refrigeration systems with total heat reclaimcapability, and a high-speed defrost system are presented. The first heat reclaim system [1]involves directional and modulating valves to communicate the superheated vapour to the aircooledcondensers or to the heat reclaim coils, and to adjust the pressure according to the outsidetemperature. A refrigerant reservoir receives liquid from both condensers and heat reclaim coils,and a sub-cooling heat exchanger with a by-pass and a special expansion valve is also provided.In the second heat reclaim system [2], heat pumps are installed on the discharge line of arefrigeration system with floating head pressure to recover the total heat and to provide comfortheating of the building during the cold periods of the year. When no heat reclaim is required, theheat pump system is used for air conditioning and sub-cooling purposes. The high-speed defrostsystem [3] mainly involves an auxiliary reservoir that operates at low pressure and isautomatically flushed into the main reservoir when liquid refrigerant accumulates to apredetermined level. It creates a pressure differential across the evaporators, sufficient to performquickly defrost cycles, even at low compressor head pressures. The experimental evaluation ofthe mentioned innovations will be completed during the next dominated heating season, notablyin order to demonstrate their energy performances in a cold climate, comparatively with those ofa conventional system, also instrumented.1. IntroductionThe purpose of the refrigeration system in a supermarket is to provide cooling to the refrigerateddisplay cases and walk-in boxes. In cold climates, the major contribution of the electric energyuse and demand comes from the refrigeration system (around 50 %). In fact, almost 100 % of thesupermarkets are there still constructed with that type of equipment. The compressors, generallyof the semi-hermetic type, are located in a machine room, normally on mezzanine, and mountedon racks with all necessary piping, valves, and electrical components needed for the operationand control. Remote air-cooled or evaporative condensers used in conjunction with multiplecompressors are usually installed on the roof, and all refrigerated fixtures employ directexpansionrefrigerant-air coils. The multiplexed compressors allow to continuously matchingtheir capacity with the refrigeration load, and so to operate at low head pressure. The capacitycontrol strategy commonly uses suction pressure set points, digital stepping strategy to select thecompressor combination to be operated, and cylinder unloading. The purpose is to maintain a2tight suction pressure control band, which results in operation at a higher average suctionpressure. The minimum condensing temperature setting recommended by most manufacturers is21 °C (70 °F). Hot gas defrost is normally controlled by a time clock or by demand defrost basedupon actual case requirements. Liquid sub-cooling, performed by ambient or mechanical devices,or external liquid-suction heat exchangers, increases refrigeration capacity as well as preventsthe formation of flash gas during low head pressure operation. A new technology (“liquiddelivery system”), already employed in Canada, allows to the refrigeration system to work withfloating condensing pressure depending on the ambient air temperature. This is achieved byinstalling a centrifugal pump on the line of liquid thus providing the necessary pressuredifferential for the proper operation of the expansion valve and reducing the condensingtemperature up to 10 °C (50 °F), depending on ambient air temperature. This technology couldproduce energy savings up to 35 % of the total energy cost, but it creates difficulties in the fieldof heat reclaim because the air to be heated is warmer then the refrigerant to be cooled. When aheat reclaim is required, the condensing pressure has to be raised artificially in order to achieveproper heat transfer, thus losing the benefits of the liquid delivery system. The majority ofsupermarkets in Canada take advantage of the large amount of heat rejected through therefrigeration system by using this heat for space or water heating. Generally, when space heat iscalled for, a three-way valve is activated, directing the refrigerant discharge to a heat reclaim coillocated in the central air handler. The refrigerant then passes to the condenser where anyremaining condensing of the refrigerant occurs. Control of heat reclaim is normally handledthrough a two-stage thermostat which allows to recover between approximately 20 % and 50 %of total heat rejection during a full or partial condensing. The condenser is flooded by the use ofa liquid holdback valve, raising the condensing temperature to the desired value, usually to 35 °C(95 °F).During the last few years, two of the most innovating refrigeration contractors have done severalimprovements of their traditional multiplexed systems that are still largely employed in Canada.These improvements concern notably the heat recovery and defrost cycle optimisation. The firstobjective was to satisfy up to 100 % the space heating needs with heat reclaim, thus eliminatingthe use of natural gas or other fossil combustibles for heating. The second objective was toreduce the defrost cycle’s length in order to improve the quality of foodstuff and, simultaneously,to reduce the energy losses normally associated with the defrost mode. This paper describes twooriginal heat reclaim methods [1; 2] and a third invention allowing to obtain defrost cycles athigh speeds [3]. The first systems integrating these new technologies were already beeninstrumented and are presently monitored by LTEE laboratory in collaboration with the abovementioned inventors and supermarket’s owners. The main objective is to determine in real timethe energy and operational performances and to provide, eventually, some improvements. Thenext heating dominated season (winter) have to provide complete information about theefficiency of the new mentioned heat reclaim and defrost methods.32. “RSD” Heat Reclaim MethodThe “RSD” heat reclaim method, already implemented in several new supermarkets in Canada,involves a high-efficiency multiplex refrigeration system with integral (100 %) heat reclaimconcept and a modulating valve for controlling the discharge pressure of the compressors [1].One of these supermarkets (Métro-Richelieu), sited in north area of Montreal, with a total surfaceof 3,711 sq.m (38,000 sq.ft), was recently instrumented by the LTEE. The total capacity of thelow temperature rack is about 65 kW (220,000 Btu/h), while the total capacity of the mediumtemperature rack is 284 kW (970,000 Btu/h). This supermarket also includes a heat reclaimsystem for domestic hot water heating, a new fast defrosting concept (see section 3), and agroundwater cooling circuit (Figure 2.1). Supplementary cost for the heat reclaim concept onlyis about 55,000 CD$ (2000). Annual savings for space and hot water heating are estimated at22,000 CD$, and the pay-back period, at 2.5 years.It is well known that in a conventional refrigeration system for supermarkets the condensingpressure and temperature are subject of the ambient air temperature. During the cold period ofthe year, even if there are possibilities to reduce the condensing pressure, a high pressure isartificially maintain in order to provide proper operation of the expansion valves and of the heatreclaim coils. However, by lowing the condensing pressure, the refrigeration capacity increasesand the energy consumption decreases. It is the reason of the recent development in Canada of aliquid delivery technology which allows to the refrigeration system to work with floatingcondensing pressure depending on the ambient air temperature. This process is achieved byinstalling a pump on the liquid line and the condensing temperature could be reduced up to 10 °C(50 °F). The above mentioned technology could produce energy savings up to 35 %, but itcreates difficulties in the field of heat reclaim, especially when a recuperation of the totalcondensing heat is required, because the air to be heated is warmer then the refrigerant to be5cooled and condensed. Therefore, when heat reclaim is required, the condensing pressure has tobe raised artificially in order to achieve proper heat transfer, thus losing the benefits of the liquiddelivery system.The refrigeration company “Systems LMP” developed a system that provides a new methodfacilitating the extraction of the total condensing heat of a refrigeration system having a floatingcondensing pressure, without increase the condensing pressure during the heat reclaim periods.This concept allows to use the same heat reclaim system for air conditioning and sub-coolingpurposes, and it is adaptable to the existing refrigeration systems. A such of system was alreadyinstaled in three new supermarkets in Canada (Figure 3.1). The main aim is to prove thecapability of the supermarket to operate without natural gas for space heating.liquid delivery system are present during the heat reclaim cycle, and therefore the heat pump –heat reclaim system is easily adaptable to any existing refrigeration system. The compressor C1is used for heat reclaim and air conditioning, while the compressor C2 is used for heat reclaimand sub-cooling purposes. When the system is in “heat reclaim mode”, the suction pressure ofthe compressor C1 is maintained at a constant value corresponding to an evaporating temperatureof 10 °C (50 °F). During this mode, the condenser Cd1, the dehumidifying coil DH and the airconditioning coil AC are not operational. In “air conditioning and sub-cooling mode”, the A/C

BACKGROUND OF THE APPLICATION

[0002]1. Field of the Application

[0003]The present application relates to refrigerated enclosures of the type used in supermarkets and the like to score foodstuff and, more particularly, to a draining of liquid in such refrigerated enclosures.

[0004]2. Background Art

[0005]In supermarkets, grocery storages, and industrial storage, amongst other applications, refrigerated enclosures are commonly used to maintain foodstuff at suitable temperatures, or to freeze the foodstuff in order to preserve its freshness.

[0006]Referring to FIG. 1 of the prior art, a refrigerated enclosure is generally illustrated at 10. The refrigerated enclosure 10 is defined by a casing 11 that forms an outer shell of the enclosure 10, and within which specific temperature conditions are maintained. Shelves 12 are provided as support for the foodstuff (not shown) that will be refrigerated/frozen in the enclosure 10. A drain basin 13 is provided at a bottom of the casing 11. As such, any residual liquid will be drained via the sloping of the drain basin 13, to the drain 14/siphon 15.

[0007]It is observed that the refrigeration unit 16 is in the drain basin 13. The refrigeration unit 16 is typically coils in which a refrigerant circulates, and upon which coils ambient air is blown.

[0008]Because of the low temperatures associated with refrigerated enclosures, there is a risk that the residual liquid to be drained by the drain basin 13 will freeze. Moreover, as the refrigeration unit 16 is in some cases adjacent to the drain 14, the temperatures adjacent to the drain 14 are lower than the temperature at the shelves 12, increasing the risk of freezing of the residual liquids. A solid build-up can damage the refrigerated enclosure. For instance, coils of the refrigeration unit 16 have broken because of ice build-ups in the drain, resulting in refrigerant leakage, emergency transfer of foodstuff, and even temporary store closure for maintenance of the refrigeration system.

SUMMARY

[0009]It is therefore an aim of the present application to provide a drain monitor system for refrigerated enclosures that addresses issues associated with the prior art.

[0010]Therefore, in accordance with the present application, there is provided

[0011]Further in accordance with the present application, there is provided a build-up monitoring system in combination with a refrigerated enclosure, comprising: a refrigerated enclosure having a drain, a drain basin and a refrigeration unit adapted to maintain refrigerating conditions in the refrigerated enclosure; a build-up detector positioned with respect to the refrigerated enclosure so as to monitor a level of build-up in the drain/drain basin; a condition analyzer for receiving detection data from the build-up detector, the condition analyzer identifying from the detection data a build-up in the drain/drain basin requiring an intervention; and an interface for indicating the requirement for the intervention.

[0012]Further in accordance with the present application, there is provided a method for identifying a build-up requiring an intervention in a drain/drain basin of a refrigerated enclosure, comprising: positioning a build-up detector in the refrigerated enclosure; monitoring detection data from the build-up detector; identifying a build-up condition by comparing the detection data with at least one predetermined parameter value for a given time period; and indicating the requirement for an intervention from the build-up condition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a sectioned elevation view of a refrigerated enclosure in accordance with the prior art;

[0014]FIG. 2 is a block diagram illustrating a build-up monitoring system for refrigerated enclosures, in accordance with an embodiment of the present application;

[0015]FIG. 3 is a printout of a user-interface screen as used with the build-up monitoring system of FIG. 2; and

[0016]FIG. 4 is a flowchart of a method for identifying a build-up requiring an intervention in a drain/drain basin of a refrigerated enclosure in accordance with another embodiment of the present application.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]Referring now to FIG. 2, a build-up monitoring system in accordance with an embodiment is generally shown at 20. The monitoring system 20 is used in conjunction with a refrigerated enclosure such as the one illustrated at 10 in FIG. 1. The monitoring system 20 is provided to monitor the refrigerated enclosure for ice build-ups in the drain basin 13, and to alarm maintenance personnel when predetermined levels of build-ups are detected.

[0018]The monitoring system 20 has a control system 21, which includes a processing unit. The control system 21 is typically part of a main controller used to operate the refrigeration system of a store/building.

[0019]A build-lip detector 22 is connected to the control system 21. The build-up detector 22 is positioned within the refrigerated enclosure to monitor ice build-ups, by monitoring the drain basin 13, the drain 14 and/or the coils 16 of the refrigeration unit.

[0020]A plurality of configurations are considered for the build-up detector 22. In a first embodiment, the build-up detector 22 is a thermocouple or thermometer positioned within the drain basin 13 and/or in contact with the drain 14. As such, any ice build-up will result in a stabilization of temperature that will be identified by the monitoring system 20.

[0021]In a second embodiment, the build-up detector 22 is an optical sensor that will visually monitor the presence of an ice build-up beyond a predetermined level. Different types of optical sensors are considered with, for instance, emitters/receivers, etc.

[0022]In a third embodiment, sensors from other industries can be used in the monitoring system 20. For instance, U.S. Pat. No. 5,296,853, issued to Federow et al. on Mar. 22, 1994, discloses a laser ice detector, components of which can suitably be used to form the build-up detector 22. It is also considered to use infrared sensors.

[0023]The control system 21 receives detection data from the build-up detector 22, and transmits the data to the condition analyzer 23. The condition analyzer 23 is provided to defect ice build-up from the detection data. The condition analyzer 23 triggers an alarm signal once ice build-up beyond a predetermined level is identified by the condition analyzer 23.

[0024]In the embodiment in which the build-up detector 22 is a thermocouple, detection parameters are provided to the condition analyser 23 by way of a database 24 with such detection parameters. For instance, the detection parameters are a temperature set-point limit or a temperature range along with a time period, whereby detection of a temperature above the set-point limit for more than the time period will have the condition analyzer 23 trigger the alarm signal.

[0025]The time period used by the condition analyzer 23 filters out punctual perturbations, such as the shelving of new produces that are at room temperature. In such cases, liquids dropping from these products and reaching the drain are temporarily above refrigerated temperatures, and should not be considered as a build-up. Therefore, monitoring such temperatures for an extended time period allows the products to cool down prior to an alarm being triggered.

[0026]Moreover, the time period can be used to monitor temperature variations. For instance, temperature readings in refrigerated enclosures 10 vary as a function of numerous factors: refrigerant temperature, air temperature, enclosure doors being opened, new products being shelved in the enclosure 10. If there is a build-up on the build-detector 22 measuring the temperature, the build-up will act as thermal insulation that will generally prevent temperature variations in the readings of the detector 22. Accordingly, in an embodiment, a uniform temperature over an extended time period is identified as a build-up by the condition analyzer 23.

[0027]The database 24 is writable, such that the detection parameters are changeable. For instance, if a defrost cycle is run to melt frost on the coils, it may be required to change the detection parameters in the database 24, although it is preferred that the detection parameters be set so as to exclude a defrost cycle from being detected as ice build-up. Another example in which it is required to change the detection parameters is when the temperature of operation of the refrigerated enclosure is changed (i.e., going from refrigerating meats to vegetables).

[0028]In the embodiment in which the build-up detector 22 is an optical sensor or like sensor, the detection data may simply be decoded by the condition analyzer 23, such as to identity detected build-up signals from the detection data. The database 24 of detection parameters may represent a filter to ensure that the alarm signal is not triggered accidentally. For instance, if an attendant triggers accidentally the optical sensor into detecting an ice build-up, the detection parameters are typically set to prevent an alarm being triggered by such action.

[0029]It is considered to provide the monitoring system 20 with a plurality of build-up detectors 22, with complementary features. For instance, optical sensors can be used in combination with thermocouples, to increase the accuracy of the detection.

[0030]Still referring to FIG. 2, the monitoring system 20 has an interface 25 that may be used to display the detection data in suitable format. For instance, referring to FIG. 3, a GUI screen 25A is illustrated, and shows a temperature detected in a refrigerated enclosure as a function of time. It is seen that a graph shows a pair of peaks on screen. The peaks are typically the result of defrost cycles being run to remove frost on the coils of the refrigeration units 16 (FIG. 1). The interface 25 may project data that is viewed on a periodic basis by an operator so as to detect ice build-up.

[0031]Alternatively, an alarm 26 may be provided, whether on site or through the interface 25 (e.g., in the form of a pop-up window), to indicate that maintenance is required to clear up the drain/drain basin.

[0032]The build-up monitoring system 20 described above may be conveniently retrofitted to existing refrigerated enclosures, such as refrigerated enclosure 10 of FIG. 1. More specifically, considering that most industrial refrigeration systems have a centralized processing unit, the condition analyzer 23 may be installed in the centralized processing unit, with the build-up detector/detectors 22 being connected to the centralized processing unit (e.g., wireless) to provide the detection data to the condition analyzer 23.

[0033]FIG. 4 generally illustrates an embodiment for implementing the method for identifying a build-up requiring an intervention in a drain/drain basin of a refrigerated enclosure at 30.

[0034]In Step 32, at least one of the build-up detectors 22 is installed in the refrigerated enclosure 10 so as to monitor the drain basin 13 or drain 14 for ice build-ups.

[0035]In Step 34, the detection data provided by the build-up detector 22 is monitored. The monitoring is continuous, but may be paused in maintenance periods, such as during a defrost cycle.

[0036]In Step 36, a build-up condition is identified from monitoring of the detection data, over a given time period. The detection data is as a function of the types of build-up detector 22 selected: temperature, visual presence of build-up.

[0037]In Step 38, indication is made to maintenance personnel that an intervention is required due to a build-up condition. For instance, maintenance personnel on-site or off-site may be warned by way of an alarm.

Le président du Groupe CSC, Serge Dubé, apparaît devant un frigo du magasin laboratoire aménagé à des fins d'étude.

(Photo: Pierre Langevin)

L'Eco-System mis au point par le Groupe CSC permet de réduire les coûts de réfrigération et de rejeter moins de gaz à effet de serre dans l'environnement.

(Photo: Pierre Langevin)

Un frigo écologique fabriqué à Les Coteaux

Actualité > Environnement

Le Groupe CSC établi dans le parc industriel à Les Coteaux vient de mettre au point un système de réfrigération unique au monde pour les marchés d'alimentation qui entraînera des économies appréciables au niveau énergétique. Ce nouveau produit s'appelle l'Eco-System.

Ce frigo révolutionnaire allie plusieurs fonctions. Outre la réfrigération bien entendu, il peut également être à la fois un équipement de climatisation, ventilation, déshumidification, chauffage et de contrôle.

En entrevue au JOURNAL, le président du Groupe CSC, Serge Dubé, a mentionné que l'Eco-System va permettre de réduire de façon importante les gaz à effet de serre dans l'environnement avec l'élimination du réfrigérant synthétique.

Il a indiqué qu'un kilo de réfrigérant synthétique rejette 3,5 tonnes de CO2 dans l'atmosphère. «Dans les gros supermarchés, il se perd 300 kilos de réfrigérant par année», révèle M. Dubé.

Pour parvenir à commercialiser le produit, ce dernier a dû consacrer beaucoup de temps, de recherches et d'énergie. Une quinzaine d'années ont été nécessaires mettre au point un tel frigo tout aussi efficace.

«Depuis 1994, on travaille pour réduire les pertes de réfrigérant et pour améliorer les coûts de chauffage. Il était également important d'améliorer la qualité du produit et le rendement de la machine de réfrigération. L'Eco-System va faire tout en un, soit le contrôle de gestion du bâtiment», explique Serge Dubé.

Pour y parvenir, le grand manitou du Groupe CSC a effectué des séjours en Chine, Australie, Allemagne et Italie pour aller chercher les meilleures connaissances technologiques dans ce domaine de pointe bien précis.

«J'ai travaillé avec les meilleurs au monde en technologie pour voir ce qui se faisait ailleurs. J'ai pris ce qu'il y avait de bon pour l'environnement, la climatisation, le contrôle et le chauffage. On peut faire d'énormes progrès pour la planète. Les gens sont plus conscients de l'environnement que par le passé», a fait remarquer M. Dubé.

Magasin laboratoire

Le Groupe CSC a loué des locaux dans le but de simuler un magasin de 25 000 pieds carrés afin d'étudier si l'Eco-System répond aux attentes. Il s'agit en fait d'un magasin laboratoire comportant des frigos.

«Depuis un an, nous avons fait des essais, des améliorations et nous avons réglé des problèmes. Les résultats sont positifs», explique Serge Dubé.

Ainsi, les supermarchés équipés de l'Éco-System verront leurs coûts d'exploitation et d'entretien diminués de façon significative puisque la consommation d'énergie est réduite au minimum, si l'on se fie à M. Dubé.

En plus, il affirme que le système élimine pratiquement les coûts reliés au chauffage puisque la récupération de chaleur permet souvent de chauffer la totalité du magasin. Les frais d'entretien seraient moins coûteux de 30 %.

Le nouveau système de réfrigération permettra de garder les aliments plus longtemps, ce qui occasionnera moins de pertes pour les détaillants. Il y a donc des économies à faire sur la qualité des produits et le service après-vente.

Environ 20 personnes travaillent uniquement sur ce projet, que ce soit pour la mise en marché, les améliorations, le branchement et autres.

L'Eco-System pourra être adapté à la taille des supermarchés. «Il n'y a aucune limite quant aux produits qui peuvent être réfrigérés», estime M. Dubé. Depuis 1994, c'est un montant de 4 millions $ qui a été investi pour ce projet spécifique.

Magasins intéressés

Il va sans dire que Serge Dubé fonde de grands espoirs sur l'Eco-System qui sera commercialisé prochainement.

D'ailleurs, certains magasins se sont montrés intéressés à acquérir cette nouvelle technologie dont le nouveau IGA à Coteau-du-Lac qui devrait ouvrir ses portes dans les prochaines semaines.

D'autres ententes ont été signées avec d'importantes chaînes d'alimentation, dont des marchés IGA et Metro à Laval, Québec et Cookshire dans les Cantons de l'Est.

C'est la compagnie Réfrigération S. Dubé, une division du Groupe CSC, qui installe le système et effectuera le service après-vente.

Le coût unitaire de chaque Eco-System variera entre 200 000 $ et 1 million $ selon la taille du magasin. «Ça va être du cas par cas», signifie M. Dubé.

«Nous allons rencontrer les chaînes spécialisées. Le prochain mois s'avère une étape cruciale. D'ici la fin de l'année, il y aura une dizaine d'Eco-System en opération», soutient le président.

Le marché canadien compte à lui seul, près de 6500 détaillants en alimentation. Si tout va bien, M. Dubé estime que le chiffres d'affaires du Groupe CSC pourrait passer de 20 millions $ à 100 millions $ d'ici les cinq prochaines années.

Pour répondre à la demande, l'entreprise compte investir 1 million $ et agrandir ses installations de 20 000 pieds carrés aménagées en 2007 sur la rue Royal. «Si tout fonctionne comme prévu, il y aura un ajout éventuel de 15 000 pieds pour un total de 35 000 pieds carrés», révèle Serge Dubé.

Le nombre d'emplois devrait doubler. Une trentaine de personnes oeuvrent actuellement à l'usine des Coteaux et l'on prévoit engager 30 autres employés. Globalement, le Groupe CSC emploie 130 personnes un peu partout à travers la province au sein de diverses divisions.

Abstract:A refrigeration unit comprises a CO.sub.2 refrigeration circuit having a CO.sub.2 compression stage in which CO.sub.2 refrigerant is compressed, a CO.sub.2 condensation stage having a tank in which CO.sub.2 refrigerant is accumulated in a liquid state, at least one of pressuring means and an expansion stage to direct the CO.sub.2 refrigerant from the CO.sub.2 condensation stage to a CO.sub.2 evaporation stage in which CO.sub.2 refrigerant absorbs energy to refrigerate. A condensation circuit has a second refrigerant being circulated between a second compression stage, a second condensation stage, a second expansion stage and a second evaporation stage. A heat-exchanger unit by which the CO.sub.2 refrigerant from the CO.sub.2 refrigeration circuit is in heat exchange with the second refrigerant in the second evaporation stage such that the second refrigerant absorbs heat from the CO.sub.2 refrigerant to at least partially liquefy the CO.sub.2 refrigerant for the CO.sub.2 condensation stage. A defrost circuit directing defrost CO.sub.2 refrigerant from the CO.sub.2 compression stage to the CO.sub.2 evaporation stage to defrost at least one evaporator of the CO.sub.2 evaporation stage, the defrost CO.sub.2 refrigerant being subsequently returned to the CO.sub.2 refrigeration circuit.

Mais la compensation n'est qu'une pratique transitoire. La seule alternative viable passe par la réduction de nos émissions. Sur-la-Toile.com invite les internautes à appliquer 20 trucs pour diminuer efficacement la production de gaz à effet de serre de leur matériel.

Des choses aussi simples que d'activer la mise en veille automatique du moniteur, de passer en mode hibernation lorsque le PC est inutilisé, ou de désactiver l'économiseur d'écran, peuvent réduire la consommation électrique d'un ordinateur de bureau de 60 %2. De surcroît, l'Internet permet désormais d'optimiser ou d'éviter les déplacements en planifiant du covoiturage ou en utilisant la vidéoconférence.

En d'autres termes, on pourrait non seulement diminuer la production de CO2 du matériel qui nous permet de surfer sur le net, mais même envisager de la neutraliser entièrement grâce aux pratiques innovantes qu'il rend accessibles.

Alors, un Web 2.0 sans CO2 ? Et si c'était possible !? Supported By Ultimatummedia.comAnthropogenic CO2 Absorption by the World's OceansAnthropogenic CO2 Absorption by the World's Oceans

Reference
Khatiwala, S. Primeau, F. and Hall, T. 2009. Reconstruction of the history of anthropogenic CO2 concentrations in the ocean. Nature 462: 346-349.Background
The release of fossil-fuel-derived CO2 to the atmosphere by human activity has been claimed by many to have played a dominant role in 20th-century global warming; and the authors note that the world's oceans play "a crucial role in mitigating the effects of this perturbation to the climate system." Hence, it is important to determine whether or not - and by how much - the strength of this mitigating factor might be changing with the passage of time.What was done
Khatiwala et al. derived, as they describe it, "an observationally based reconstruction of the spatially-resolved, time-dependent history of anthropogenic carbon in the ocean over the industrial era [AD 1765 to AD 2008]," based on the known history of the air's CO2 concentration and analyses of the oceanic transport of "a suite of well sampled oceanic tracers such as chlorofluorocarbons, natural ¹⁴C, temperature, and salinity from the GLODAP and World Ocean Atlas databases."What was learned
The three U.S. researchers determined that the amount of anthropogenic CO2taken up by the world's oceans has been continually increasing with the passage of time, pretty much in phase with the atmosphere's ever-increasing CO2 concentration, as shown in the figure below.
Atmospheric CO2 concentration and oceanic uptake rate of anthropogenic carbon (with shaded error envelope) plotted against time. Adapted from Khatiwala et al. (2009).In addition, Khatiwala et al. note that after the sharp increase in the anthropogenic CO2 uptake rate after the 1950s, there has been "a small decline in the rate of increase in the last few decades." However, as may readily be seen in the figure above, this latest deviation of the oceanic CO2 uptake rate (from its correlation with the atmosphere's CO2 concentration) is similar to those of prior such deviations, which have been of both a positive and negative nature. And the size of the shaded error envelope associated with the anthropogenic CO2 uptake rate allows for the possibility that its correlation with the atmosphere's CO2 concentration could well have been essentially perfect from about the 1860s through and including the present time.What it means
Writing about the research of Khatiwala et al. in the 19 November 2009 issue of The New York Times, Sindya Bhanoo gives a distinctly climate-alarmist slant to the scientists' findings, stating that the growth in the ocean's uptake rate of anthropogenic carbon "has slowed since the 1980s, and markedly so since 2000," with the implication that "the research suggests that the seas cannot indefinitely be considered a reliable 'carbon sink' as humans generate heat-trapping gases." In fact, Bhanoo quotes Khatiwala himself as saying that the recent trend to lower values of the ocean's uptake rate of anthropogenic carbon "implies that more of the emissions will remain in the atmosphere."

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Leader en réfrigération à QuébecSystèmes neufs ou remis à neuf de multicompresseurs « parallèle-pack » Récupération 100% de la chaleur

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CO2 Refrigeration systems

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Carbon dioxide could replace global-warming refrigerant

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Source / Source

Changements climatiques, Initiatives d'entreprises, Science et recherche, À la une...

Un frigo écologique fabriqué à Les Coteaux

Magasin laboratoire

Magasins intéressés

Leader en réfrigération à Québec
Systèmes neufs ou remis à neuf de multicompresseurs « parallèle-pack » Récupération 100% de la chaleur

Carbon dioxide could replace
global-warming refrigerant

Carbon dioxide could replace
global-warming refrigerant

CO₂ Hydrates in Refrigeration Processes