Micro-refrigeration

Future computer chips will probablly generate 10 times more heat than today's microprocessors and will require new types of cooling systems. Currently, computers are usually cooled thanks to fans and small finned devices called heat sinks, but the miniature refrigeration systems currently developed by researchers at Purdue University could offer much higher cooling power that would boost performance and shrink the size of computers. The research team, led by Suresh Garimella and Eckhard Groll, member of IIR Commission B2, focuses on designing miniature evaporators and compressors. The compressors use penny sized diaphragms, made of ultra-thin sheets of a plastic called polyimide and coated with an electrically conducted metallic layer allowing the diaphragm to be moved back and forth to produce a pumping action using electrical charges, a process called electrostatic diaphragm compression. The engineers were also among the first to precisely measure flow boiling and vaporization inside microchannels sometimes thinner than a human hair. They have also developed a computational model for compressor design, making it possible to determine how many diaphragms to use, how to stack them (in parallel or in series). In one direction pressure rises; in the other, more volume is pumped. Berstch, a PhD student created mathematical equations for the design of miniature evaporators. Learning how to manufacture the devices at low cost is another major challenge, with industry requiring a cost of USD 30 each.