seal  Purdue News

June 23, 2004

Conferences tackle key issues in air conditioning and refrigeration

WEST LAFAYETTE, Ind. – Hundreds of researchers from around the world will meet at Purdue University July 12-15 to discuss the hottest new air conditioning and refrigeration technologies, including designs aimed at reducing global warming, conserving energy and cooling future computers.

Eckhard Groll working on a prototype
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"We expect to have about 600 people from 30 countries," said Eckhard Groll, an associate professor of mechanical engineering. Groll worked with mechanical engineering professors Werner Soedel and James Braun to organize the 10th International Refrigeration and Air Conditioning Conference and the 17th International Compressor Engineering Conference.

The conferences, organized through Purdue's Ray W. Herrick Laboratories, take place every two years at the university. Researchers have submitted 113 technical papers for this year's refrigeration and air conditioning conference and 104 papers for the compressor conference, Groll said.

Sessions will include an update on ozone depletion and climate change, a panel discussion on the use of carbon dioxide as an environmentally friendly alternative to more conventional refrigerants and a presentation on homeland security issues for building systems.

Groll said Purdue is a major player in air conditioning and refrigeration research, and last year the university organized the International Congress of Refrigeration in Washington, D.C.

Because compressors, air conditioners and refrigerators are responsible for a huge portion of the world's total energy consumption, many talks will deal with energy efficiency and innovative technologies, he said.

Compressors range from one-horsepower units in household appliances to powerful monsters that have hundreds or even thousands of horsepower and are used for such applications as pumping natural gas and creating seismic waves for ocean exploration.

Engineers are constantly trying to improve compressor designs to make them faster, quieter, more reliable and more energy efficient.

"In the U.S., power consumption of commercial buildings is about one-third of the total power consumption in the nation," Groll said. "Air conditioning represents a significant portion of that one-third."

Braun recently completed a three-year project funded by the state of California and industry to create a computerized system that uses software and sensors to automatically detect and diagnose problems in commercial air conditioning units and then recommend specific repairs. The system promises to save time and money by automatically sending diagnostic information to a central location through the Internet or other means, quickly alerting technicians to problems and reducing the need for field tests.

"The system can reduce service costs, improve overall comfort conditions in buildings and improve energy efficiency," Braun said.

A special session will be held on this subject, called automated diagnostics for cooling equipment.

"There is really a lot of activity on this general topic, and we've made some significant contributions," said Braun, who has written three technical papers on the subject with doctoral student Haorong Li.

Researchers also are working on a wide range of innovative refrigeration concepts that are less harmful to the environment than conventional technologies.

"I think environmental issues are in the forefront," Groll said. "There is a lot of research going on to develop alternative refrigerants that don't harm the ozone layer or cause global warming."

For example, the meeting will include a session devoted to research regarding refrigeration and air conditioning systems that use carbon dioxide as a refrigerant

Carbon dioxide was the refrigerant of choice during the early 20th century but was later replaced with man-made chemicals. Now carbon dioxide may be on the verge of a comeback, thanks to technological advances that include the manufacture of extremely thin aluminum tubing called "microchannels."

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. 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, Groll said.

Carbon dioxide offers few 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. Carbon dioxide, however, is promising for systems that must be small and lightweight, 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.

During the 1930s carbon dioxide was replaced by synthetic chlorofluorocarbon refrigerants, known as 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. Groll said that recent advances in manufacturing and other technologies are increasing the practicality of using natural refrigerants such as carbon dioxide and ammonia.

Most of the conference sessions will be in Purdue's Stewart Center. Registration will be in the east foyer from 8-10 a.m. Monday, July 12.

Conference highlights will include:

• 10-11:45 a.m. July 12. Loeb Theatre in Stewart Center. Welcome by Purdue President Martin C. Jischke and keynote address on ozone depletion and climate change by David Fahey, a research scientist from the National Oceanic and Atmospheric Administration's Aeronomy Laboratory

• 1-3 p.m. July 12, Stewart Center, Room 310. 9:20-11:45 a.m. July 14, Stewart Center, Room 202. Braun, Groll and graduate student Yang Li will present two papers that address how the buildup of dust on a segment of an air conditioner called the heat exchanger impacts the overall performance of air conditioning equipment used in commercial buildings. Those talks also will address how using filters to prevent dust buildup affects energy use.

• 1-3 p.m. July 12. Stewart Center, Room 218. A team led by Douglas E. Adams, an assistant professor of mechanical engineering, will present a technical paper about a complex model that shows the entire workings of a high-performance automotive air conditioning compressor. The engineers used their mathematical model to pinpoint the source of a nagging design flaw that has caused noise problems, and two patents for design modifications have been filed.

• 8-9 a.m. July 13. Fowler Hall, Stewart Center. Session on "homeland security issues for building systems: past, present and future" by James Hill, director of the Building Fire and Research Laboratory at the National Institute of Standards and Technology.

• 9:20-11:45 a.m. July 13. Stewart Center, Room 202. Braun, Groll and doctoral student Satyam Bendapudi will present papers on "dynamic modeling" of a large chiller used to cool structures such as office buildings, hospitals and airports. The mathematical model can be used for testing "feedback controllers" or diagnostic methods that are far less expensive than performing laboratory and field tests.

• 9:20-11:45 a.m. July 13. Stewart Center, Room 202. Braun and doctoral student Xiaotang Zhou will present a paper on dynamic modeling of coils used to cool and provide dehumidification for buildings. The mathematical model is used to test systems less expensively than conventional methods.

• 1-3 p.m. July 13. Stewart Center, Room 202. Braun and doctoral student Haorong Li will present two papers about their work on automated diagnostics for cooling equipment. One paper presents a general method for using low-cost measurements to diagnose many problems happening simultaneously. The second paper addresses the overall economic benefits of automated detection and diagnosis.

• 3:20-5:20 p.m. July 13. Stewart Center, Room 310. Groll and doctoral student Suwat Trutassanawin will present a technical paper about a new design of a miniature-scale refrigeration system that could be used to cool computer chips in the near future. The system is similar to conventional refrigerators, except that it is small enough to fit in a personal or laptop computer.

• 3:20-5:20 p.m. July 13. Stewart Center, Room 214. Groll, Braun and visiting scholar Frank Yi from Nanjing Aotecar Refrigerating Co., will present a two-part technical paper on a new mathematical model that industry can use to improve the efficiency of so-called "scroll compressors" found in automotive air conditioners. Groll and Braun have developed the complex models for other compressors as well. The models can be used to predict performance and pinpoint where improvements need to be made in a particular design.

• 8-9 a.m. July 14. Fowler Hall, Stewart Center. Session and panel discussion on the current status and future prospects for using carbon dioxide in air conditioning, refrigeration and heat pumps.

• 8-9 a.m. July 15. Fowler Hall, Stewart Center. Session and panel discussion on future heating, ventilation, air conditioning and refrigeration systems.

Writer: Emil Venere, (765) 494-4709,

Sources: James Braun, (765) 494-9157,

Eckhard Groll, (765) 496-2201,

Werner Soedel, (765) 494-8613,

Purdue News Service: (765) 494-2096;

Note to Journalists: Electronic copies of papers being presented by Purdue researchers are available from Emil Venere, (765) 494-4709,

Related Web site:
Conference Web site

Eckhard Groll, an associate professor of mechanical engineering at Purdue University, works on a miniature-scale refrigeration system that could be used to cool computer chips in the near future. The system is similar to conventional refrigerators except that it is small enough to fit in a personal or laptop computer. Researchers will present a technical paper about the work during an international conference in July on air conditioning, refrigeration and compressors. (Purdue News Service photo/David Umberger)

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