Carbon Dioxide Could Replace Global-Warming Refrigerant

ScienceDaily (July 4, 2000) — 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 Eckhard 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.

Co2 as a Refrigerant

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 requiresadvanced 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.

China Refrigeration: Walking on the CO2 path - Part I

The world’s third largest trade show for heating and cooling was, as expected, dominated by solutions for conventional refrigerants. However, a surprising number of global players presented CO2 components set to be sold on the Chinese market in a few years time. In a technical seminar, Bitzer updated Chinese experts on latest developments regarding CO2 compressors.

At the China Refrigeration, held last week from 5-7 April in Guangzou, companies known to be involved in CO2, nearly animously agreed that the natural refrigerant would certainly be a solution to be taken to the Chinese market in the near future. At present however, and also looking at cost cutting tendencies in the industry, CO2 would remain mainly in the testing phase, with commercialisation to be expected over the next few years.

Technical Seminar on CO2 compressors

In its technical presentation to around 100 industry experts and engineers, German compressor manufacturer Bitzer updated on the performance and operation of its CO2 range. In a packed room, Bitzer representatives from China started off by explaining basic characteristics of R744, its behaviour compared to R22 or R404a, differences between transcritical and subcritical operation, and the compact design of CO2 compressors. The compressor maker then went on to elaborate on the different system layouts used with R744, specific design options, and efficiency comparisons between the natural and chemical refrigerants.

Participants were highly interested in technical details regarding high-pressure R744 systems. Lively discussions centred around the questions of oil return, the materials used for CO2 compressors, the preferred hybrid systems used in European supermarkets, and better cooling systems in a Chinese test system using R404a-R744.

Liquid CO2 - an alternative to freon for the frozen food shipping industry

Frozen Food Digest, Oct, 1992 Frozen Food Digest, Oct, 1992

Cryocon Containers Inc., a publicly owned Vancouver, Canada based Company and their joint venture partner Pacific Shipping Systems Inc., have introduced the first 48 foot Domestic Intermodal container to the U.S. frozen food industry using liquid CO2 as the refrigerant, replacing current mechanical CFC based freon coolants.

Continued testing of the finished model using state of the art container technology has reaffirmed the superiority (proven earlier in railcars) of the system over conventional mechanical reefers. One recent test, initiated jointly with Burlington Northern Railway and their customer Twin City Foods, a leading National Distributor, entailed transporting a load of frozen corn at zero degrees F. from Ellensburg, Washington to Lake Odessa, Michigan. The trip was five and a half days with the load arriving at zero degrees F. Tom Matheson, Traffic and Distribution Manager at Twin City Foods was quoted as saying "everything went perfect" and "we feel that the cryogenic container will fit into the frozen market quite well."

The system, which has no mechanical moving parts, is cost competitive to build, economical to operate, allows competitive cubic space for product and has no maintenance requirements necessary to conventional mechanical reefers. The advantages bring overall shipping costs down dramatically.

The CO2 cryogenic technology was first introduced in the early 1980's when Van Thomsen, then of Liquid Air Corporation, together with the American Frozen Food Institute and Burlington Northern Railway built a working prototype railcar with a system whereby liquid CO2 is pumped into a bunker located in the top of the car where it turns into dry ice snow. Through the natural process of warm air rising inside the product storage area, the dry ice snow sublimates and cryogenic gas drops down and maintains the temperature of the frozen product.

Cryocon Containers Inc., using the latest Thomsen technology, is now able, for the first time, to install their system into thin skinned Intermodal and I.S.O. containers as well as over-the-road truck trailers.

The supply of commercial liquid CO2 is readily available, inexpensive and also causes no net effect on the ozone layer.

Cryocon is currently building an over-the-road trailer for an International food distributor, five 40 foot I.S.O. ocean containers and five 48 foot Intermodal containers for marketing purposes to frozen food processors, third party shippers and premier shipping lines. The company uses established quality manufacturers under license to build the containers incorporating the technology from the ground up.

COPYRIGHT 1992 Frozen Food Digest, Inc.

COPYRIGHT 2008 Gale, Cengage Learning

Modine Awarded Second Defense Contract to Develop Alternative Air Conditioning Systems Using CO2 Refrigerant for HMMWV's

Business Wire, Nov 11, 2004

RACINE, Wis. -- Modine Manufacturing Company (NYSE:MOD), a worldwide leader in heating and cooling technology, announced today it has won a second generation contract with the United States Army, Research, Development and Engineering Command, to continue to develop alternative HVAC systems that utilize transcritical carbon dioxide (CO2) technology. Modine will demonstrate its technology on an Up-Armored M1114 High Mobility Multi-Wheeled Vehicle (HMMWV), which is in active use by the military in hot climates such as Iraq and Afghanistan as well as in Environment Control Units (ECU), used to provide space heating and cooling for equipment and personnel.

These new prototype environmental control systems and components use CO2 as the refrigerant, which provides a number of advantages over the current R134a refrigerant. CO2 is a natural refrigerant that is pulled from the air and if leaked, poses no threat to the environment. It also releases no harmful hydro-fluorocarbon (HFC) gases. It is non-toxic and non-flammable and enjoys the highest safety rating established by commercial standards.

"In extreme temperatures, around 130 degrees Fahrenheit, CO2 is an excellent refrigerant. In addition to its environmental benefits, it also cools more quickly than current systems, is more fuel efficient and takes up less space in the vehicle," said Dr. Tony De Vuono, Modine Vice President and Chief Technology Officer. "CO2 also provides excellent heating for the ECU's when operating the system in heat pump mode."

United States Senator Herb Kohl of Wisconsin, who sits on the Senate Appropriations Committee, congratulated Modine for its work with the U.S. Army. "Modine has become a leader in alternative coolant systems. This second contract for Modine allows a technology leader to focus on two major industry needs: reduce the impact of refrigerant release on the environment by learning how to best apply CO2 refrigerants and improve HMMWV air conditioning performance in extremely challenging environments."

The first generation contract, awarded in September 2003 for $1.35 million, allowed Modine to develop both climate control systems and outfit the first CO2 cooled HMMWV and ECU. "This second generation contract, valued at $2.975 million, and lasting 12 months, will allow Modine to optimize the designs for both performance and manufacturing," said Sam Collier, Modine Advanced Systems Development Manager. A fleet field trial could follow this second contract, sometime late next year, added Collier.

Army experts say the system has performance, environmental and logistical advantages over existing systems for the 9,900 pound HMMWV. "Performance comes first," said John Manzione, RDECOM's Environmental Technology Team Leader and CO2 project manager. "These HMMWV's are being deployed as armored vehicles, with heavily equipped soldiers operating in extreme temperatures under very stressful conditions. A higher-performing cooling system that comes in a more compact and lightweight package offers tremendous operational advantages."

"Modine has done an excellent job of designing a first generation CO2-based cooling system that has been shown to provide quicker and deeper temperature pulldown in the most extreme battlefield conditions. We look forward to working with Modine on this next phase of development and we appreciate the continued sponsorship of the Army's Product Manager, Light Tactical Vehicles (PM-LTV)," said Manzione.

John Dolney, Acting Assistant Product Manager for Up-Armored HMMWV, PM-LTV added, "It's good to see product improvement initiatives that show promising performance benefits, while at the same time demonstrating superior environmental friendliness. Reducing basic vehicle weight will increase cargo-carrying capability and will also mean a more reliable vehicle to begin with. We look forward to Modine's second phase of development work and beyond that, the verification of production readiness for the CO2 cooling system."

Modine made history in July, when employees demonstrated the capabilities of the HMMWV operating with the prototype CO2 air conditioning system in Scottsdale, Arizona at the SAE Alternate Refrigerant Symposium. Five members of the Modine design team, along with representatives of the U.S. Army RDECOM, PM-LTV, and the Tank-Automotive & Armaments Command, offered demonstration rides in the military vehicle for automotive experts, design engineers and industry leaders. The system has also been field tested in Death Valley National Park, where it operated successfully for a three-day test under extreme conditions of up to 117 degrees Fahrenheit.

Modine has been working on CO2 HVAC technology for eight years. "With impending legislation in Europe that proposes to start phasing out R134a for automotive AC systems in 2011, Modine has successfully developed and demonstrated full systems integration capability on a number of vehicle platforms," said Steve Memory, Modine's Manager of Global HVAC Technology. "The contract with the U.S. Army has greatly helped this development work and proved that Modine's system has the durability to operate very well under extremely challenging conditions."

Modine, with fiscal 2004 revenues of $1.2 billion, employs more than 8,500 people worldwide at 35 facilities, and specializes in thermal management components, bringing heating and cooling technology to diversified markets. Modine's products are used in light, medium, and heavy-duty vehicles, HVAC equipment, industrial equipment, refrigeration systems, fuel cells and electronics. More information about Modine can be found on the Internet at www.modine.com.

Note to Editors: Photos of the HMMWV are available by contacting Lori Stafford in Modine Corporate Communications.

This news release may contain statements, including information about future financial performance, accompanied by phrases such as "believes," "estimates," "expects," "plans," "anticipates," "will," "intends," and other similar "forward-looking" statements, as defined in the Private Securities Litigation Reform Act of 1995. Modine's actual results, performance or achievements may differ materially from those expressed or implied in these statements, because of certain risks and uncertainties, which are identified on page 31 of the Company's 2004 Annual Report to Shareholders and other recent Company filings with the Securities and Exchange Commission. Specifically, this news release contains forward-looking statements regarding emerging technology and incremental business. These forward-looking statements are particularly subject to a number of risks and uncertainties, including international economic changes and challenges; market acceptance and demand for new products and technologies; the ability of Modine, its customers and suppliers to achieve projected sales and production levels; and unanticipated product or manufacturing difficulties or regulatory activity. Modine does not assume any obligation to update any of these forward-looking statements

COPYRIGHT 2004 Business Wire

COPYRIGHT 2008 Gale, Cengage Learning