sealPurdue News

July 2000

Meetings highlight hot developments
in cooling research

WEST LAFAYETTE, Ind. – About 800 engineers will converge on Purdue University in July for three international conferences to discuss the latest findings in air-conditioning and refrigeration research, including work to develop systems that use environmentally friendly refrigerants that don't cause global warming.

One of the three gatherings, the Gustav Lorentzen Conference on Natural Working Fluids, will be held for the first time in the United States. It focuses on natural refrigerants, such as carbon dioxide and ammonia, which are thought to be less harmful to the environment than synthetic chemical compounds. The two other conferences, which are held every two years at Purdue, concentrate on research aimed at improving conventional air-conditioning systems and developing entirely new technologies, such as "thermoacoustic" refrigerators that use sound waves to induce cooling. Those meetings are called the Fifteenth International Compressor Engineering Conference and the Eighth International Refrigeration Conference.

Finding ways to design more efficient air-conditioning and refrigeration systems is no small matter, considering the huge amount of energy consumed for heating and cooling, says James E. Braun, an associate professor of mechanical engineering at Purdue who heads the organizing committee for all three conferences.

"Energy usage within commercial and residential buildings, most of which is spent on heating and air conditioning, represents about a third of the total energy consumed in the United States," Braun says. The three conferences will be held concurrently at Purdue from July 23-28. New findings to be discussed by Purdue engineers will include:

• Improvements to an experimental system for monitoring the health of large, rooftop commercial air-conditioning units. Millions of the units are in operation around the world. Yet, they typically are not maintained well, causing them to run less efficiently and break down. What industry needs is an inexpensive system that automatically monitors the health of large units, alerting maintenance personnel to emerging problems before they become critical. Purdue engineers are developing such a system, which requires sophisticated software to diagnose an air conditioner's health. The latest findings, to be discussed during the conference, are improvements to a computer software tool, called an algorithm, which is able to detect and diagnose faulty behavior in the air conditioning system.

• The first comprehensive computer model that simulates the detailed operation of an innovative form of air-conditioning compressor, called a scroll compressor, now used in many types of systems. Because the model describes mathematically how the compressor performs, it is a tool that might be used for improving previous designs to boost efficiency and performance. Unlike more conventional compressors, which use a piston to increase the pressure of refrigerants, a scroll compressor uses a cylindrical pump made of two scroll-shaped halves, one rotating inside its stationary counterpart, to trap and pressurize the refrigerant. The compressors are more efficient and make less noise than conventional compressors.

• The latest work in efforts to develop thermoacoustic air-conditioning and refrigeration systems, which use sound waves instead of a conventional compressor to drive pressure changes that result in cooling. Thermoacoustic systems would replace a standard compressor-based system with a device that requires no lubrication, which would greatly simplify the design of refrigeration systems, leading to lower manufacturing and maintenance costs. However, experimental thermoacoustic systems are not nearly as efficient as conventional air conditioners. Some of the work to be presented during the conference concerns efforts to improve the efficiency.

The major sponsors for the conferences are the Ray W. Herrick Laboratories, in the Purdue School of Mechanical Engineering; the Air-Conditioning and Refrigeration Institute; the American Society of Heating, Refrigerating, and Air-Conditioning Engineers; and the Insitut International Du Froid/International Institute of Refrigeration.

More than 800 conferences and meetings are held at Purdue University annually, attracting nearly 90,000 people. Conferences during the 1998-99 fiscal year had an estimated economic impact of $15 million for the community surrounding Purdue, according to the Greater Lafayette Convention and Visitors Bureau.

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

Eckhard Groll, (765) 496-2201,

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

Purdue News Service: (765) 494-2096;

* To the Purdue News and Photos Page