The design of ARCTIC: A rotary compressor thermally insulated mu cooler

摘要

Microscale cooling to date relies largely on passive on-chip cooling in order to move heat from hot spots to alternate sites. Such passive cooling devices include capillary pump loops (CPL), heat pipes, and thermosiphons. Recent developments for active cooling systems include thermal electric coolers (TECs) for heat removal. This paper focuses on the design of an active microscale closed loop cooling system that utilizes the Rankine vapor compression cycle. In this design, a rotary compressor will generate the high pressure required for efficient cooling and will circulate the working fluid to move heat away from chip level hot spots to the ambient. The rotary compressor will leverage technology gained from the rotary engine power system (REPS) program at UC Berkeley, most specifically the 367 mm(3) displacement platform. The advantage of a Wankel (Maillard) compressor is that it provides six compression strokes per revolution rather than a single compression stroke common to other popular compressors such as the rolling piston. The current Wankel compressor design will achieve a theoretical compression ratio of 4.7:1. The ARCTIC (a rotary compressor thermally insulated mu cooler) system will be a microscale hybrid system consisting of some microfabricated (or MEMS) components including microchannels, in plane MEMS valves, and MEMS temperature, pressure and flow sensors integrated with mesoscale, traditionally machined steel components, including the compressor itself. The system is designed to remove between 45 W of heat at 1000 rpm using R-134a but the system is easily scaleable through a speed increase or decrease of the compressor. Further, a vapor compression cycle using R-134a operating between 258 and 3 10 K has a theoretical coefficient of performance (C.O.P.) of approximately 4.6. While this calculation does not include pressure losses, compressor inefficiency, or heat transfer losses, it provides ample room for significant improvement over comparable TECs with C.O.P.s of approximately 0.1-0.2. Finally, a thermal circuit analysis determines that the time constant to achieve refrigeration temperature at the evaporator in 12 s is possible. (c) 2006 Elsevier B.V. All rights reserved.