July 6, 2006|
Conferences tackle key issues in air conditioning and refrigerationWEST LAFAYETTE, Ind. Hundreds of researchers from around the world will meet at Purdue University July 17-20 to discuss the hottest new concepts for refrigeration and air conditioning technologies, including designs aimed at reducing global warming and noise pollution, conserving energy and cooling future computers.
Most of the conference sessions will be in Purdue's Stewart Center, Room 302. Registration will be in the east foyer from 8-10 a.m. Monday, July 17.
"We take it for granted, but many places around the world would be virtually uninhabitable without air conditioning," said Eckhard Groll, a Purdue professor of mechanical engineering. "Modern life without refrigeration would be impossible because we use it for everything from medical applications to food preservation and distribution."
Sessions will include talks about technologies that use carbon dioxide as an environmentally friendly alternative to more conventional refrigerants; presentations on new designs for compressors and other components in air conditioning and refrigeration units; more accurate computational models to simulate the operation of refrigeration systems; and a glimpse at futuristic technologies, such as experimental approaches that harness sound waves to induce cooling.
"The list of topics is really comprehensive, covering many areas that are critical to industry and commerce," said James Braun, a Purdue professor of mechanical engineering. "One session will focus entirely on industrial refrigeration. It's really important to stress that many of these research projects are being led by graduate students, who are the primary innovators."
The conferences are organized by faculty from Purdue's Ray W. Herrick Laboratories, in cooperation with sponsoring and participating organizations including the American Society of Heating, Air Conditioning, and Refrigerating Engineers and the International Institute of Refrigeration.
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. Compressors play a vital role in the cooling cycle because they are needed to increase the pressure of refrigerant so that it can absorb heat and induce cooling.
"Research in compressors has recently focused on technologies that are cleaner and quieter," Groll said. "We still have tremendous environmental concerns associated with refrigeration, in part because refrigerants have a high global warming potential."
Scientists and engineers are trying to improve the efficiency of systems that use carbon dioxide as a refrigerant, and many papers will deal with compressor designs and methods for reducing the overall energy consumption of CO2 systems. While carbon dioxide offers promise as a more environmentally friendly refrigerant, technologies that use CO2 must be perfected to increase energy efficiency.
Some designs include small turbines or piston devices that generate electricity or drive a shaft to help run the compressor. The devices take advantage of the fact that the pressure of the refrigerant must be lowered at a certain point in the refrigeration cycle, and the devices make use of energy that is ordinarily wasted during this portion of the cycle.
"Conventional systems use valves or other devices to reduce the pressure, but then you are just throwing away energy," Groll said. "Carbon dioxide systems, operating with turbines and other devices for recovering energy, are more practical."
The energy-generating devices serve two purposes: they lower the pressure while also generating electricity.
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, because of technological advances.
Several papers will detail research in heat transfer and heat exchangers, including systems that use microchannels instead of conventional tubing for circulating refrigerant.
In another key research area, the conference includes three sessions on noise control.
"Noise is still a very important issue for compressors, especially in heavily populated cities in Asia and Europe," Groll said.
Researchers from universities and companies in Asia and elsewhere are presenting about two dozen papers focusing on quieter designs.
Other papers being presented during the conference focus on energy savings.
Researchers at Purdue's Herrick laboratory are designing a new type of compressor called a bowtie compressor, which could be used in domestic refrigerator-freezers to save energy. The design contains two opposing compression chambers in a shape resembling a bowtie.
"You can vary the displacement of the compressor, which means how much refrigerant it sucks in and how much it compresses, while maintaining relatively constant efficiency," said Groll, who worked with doctoral student Jay Kim to develop the new compressor design.
Another session will be dedicated to the most unconventional, or "novel systems," including thermo-acoustic designs that use sound waves to induce cooling, in research led by Braun, Luc Mongeau, a Purdue mechanical engineering professor, and doctoral student Insu Paek.
Groll, Braun, mechanical engineering professor Galen King, and doctoral student Jason Hugenroth also are working on a new type of experimental design called an Ericsson-cycle cooler, which uses an exotic concept called isothermal expansion to induce cooling. Unlike conventional refrigerators, in which a refrigerant gas condenses into a liquid after absorbing heat, the refrigerant remains a gas in the Ericsson-cycle. The system could run on air and water, instead of synthetic refrigerants, promising a green alternative to conventional air conditioning and refrigeration technologies.
"To make the Ericsson cycle design work properly you need isothermal compression, which means that you are both compressing and cooling the gas at the same time, which prevents the gas from turning into a liquid," Groll said. "If you can do this successfully, you can use less energy to run a compressor, but it's a very difficult process."
The gas is kept cool by adding a liquid to it as the gas is being compressed.
"But this is complicated because you then have both a gas and a liquid existing at the same time in the system, and you have to separate the two after the compression portion of the cycle is completed," Groll said. "Student Jason Hugenroth came up with the concepts that allowed practical implementation of the Ericsson-cycle cooler, designed a prototype and performed an extensive evaluation."
The conference organizing committee includes several faculty members from the Herrick Laboratories, including Braun, general conference chair and refrigeration conference chair; Groll, who is compressor conference chair; Douglas Adams, an associate professor of mechanical engineering who is compressor conference program chair; Lorenzo Cremaschi, a post-doctoral research associate in mechanical engineering who is refrigeration conference program chair; Patricia Davies, a professor of mechanical engineering and director of the Herrick Laboratories who helped organize the conferences; and Virginia Freeman, who is conference administrator.
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Eckhard Groll, a professor of mechanical engineering at Purdue University, demonstrates a prototype portable air conditioning unit that uses carbon dioxide as a refrigerant instead of conventional chemicals. The prototype has been developed as part of research funded by the U.S. Army. Carbon dioxide is a green alternative to conventional refrigerants, which cause about 1,400 times more global warming than the same quantity of carbon dioxide. (Purdue News Service photo/David Umberger)
A publication-quality photo is available at http://news.uns.purdue.edu/uns/images/+2006/groll-CO2ac.jpg
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