C. Ramaswamy, Y. Joshi and W. Nakayama
CALCE Electronic Products and Systems Consortium
University of Maryland
College Park, MD 20742
The heat dissipation rates at the chip level are projected to reach the 50-100 W/cm2 mark for some future high performance electronic systems. Liquid cooling with phase change has been demonstrated to be a very efficient technique for thermal management of such high heat dissipation rates. Past work on liquid immersion cooling using fluorocarbons has shown the advantage of using enhanced structures to reduce boiling incipience excursion and raise the critical heat flux (CHF). Thermosyphons, employing these enhanced structures are an alternative to liquid immersion and are suitable for point cooling applications, where very compact evaporators are needed. This study investigates the combined effect of sub-cooling and pressure on the performance of an enhanced microstructure based thermosyphon, which has shown very high heat transfer rates (up to 100 W/cm2 with a wall superheat of 27.8 oC). The pressure levels tested were partial vacuum (40-101.3 kPa), atmospheric pressure (101.3 kPa) and high pressure (101.3-370 kPa). The experiments were initiated at room temperature, and hence the sub-cooling corresponded to the difference in the liquid saturation temperature at the starting system pressure and room temperature. The results show a reduction in wall superheat values at higher pressures, at a given heat flux. The performance of the system was evaluated by defining a surface-to-ambient resistance. Results show that a partial vacuum at all heat fluxes results in better performance compared to higher pressures. The combined effect of pressure and sub-cooling was also tested for a compact evaporator and the results obtained were similar to the baseline case (larger evaporator).
Complete article is available to CALCE Consortium Members
© IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.