West Lafayette (IN) – Researchers from Purdue University claim they are getting closer to develop a much more efficient cooling system that the traditional heatsink-fan design used in many computers today. Suresh Garimella and Eckhard Groll say they can miniaturize traditional refrigerator designs to become small enough to fit in desktop computers or even notebooks.

The design the two researchers are working on is a type of vapor-compression refrigeration, which is commonly used for large-scale air-conditioning as well as your refrigerator at home. The basic concept of this technology uses a circulating liquid in different pressure states to remove heat from a device.

Typically, vapor-compression refrigeration technology, involves four main components: An evaporator, a compressor, a condenser, and an expansion valve. A refrigeration cycle begins with the refrigerant entering the compressor as a superheated vapor at low pressure. The liquid exits the compressor as vapor with higher pressure and enters the condenser, where it is condensed as heat is removed to cooling water or via air and an assisting fan to the outside of a casing. The liquid exits the condenser as a high-pressure liquid. The pressure decreases as it flows through the expansion valve where portions of the liquid turn into cold vapor. The remaining liquid then is directed to the evaporator, where the low pressure liquid is vaporized as heat is transferred from the refrigerated space. The cycle is complete by sending the liquid back into the compressor.

The idea of using this common refrigeration technology for smaller electronic devices is not entirely new and has been discussed especially in the past 8 years in numerous scientific papers. However, the challenge appears to have been to understand how these systems can work on a small scale and how especially compressors can be miniaturized.
Garimella and Groll from Purdue now claim that they have succeeded in designing tiny compressors that pump refrigerants using penny-size diaphragms. The elastic membranes are made of ultra-thin sheets of a plastic called polyimide and coated with an electrically conducting metallic layer. The metal layer allows the diaphragm to be moved back and forth to produce a pumping action using electrical charges, or "electrostatic diaphragm compression." So far, it is only one part of the refrigeration cycle, but the scientists believe that such a system can be made small enough to fit into laptops.

Unlike conventional cooling systems, which use a fan to circulate air through finned devices called heat sinks attached to computer chips, miniature refrigeration would dramatically increase how much heat could be removed, Garimella said.

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