Thermal Performance of Miniature Vapour-Compression Refrigeration System for CPU Thermal Management

In this case study, CPU liquid cooling scenarios are investigated with different heat rejection systems: conventional Air-Cooled Heat Exchanger (ACHE), and miniature Vapour-Compression Refrigerator (VCR). Unlike previous VCR research, where the evaporator is attached to the electronic device being cooled, this work considers the scenario whereby the VCR refrigerates single phase water, which is pumped in a closed loop between the cold plate and the VCR evaporator heat exchanger. Tests are performed for a range of heat input power (100 W-700 W) and water volumetric flow rates (1 LPM - 3.5 LPM) for two compressor speeds (2200 RPM & 6500 RPM) of the VCR. The results show that the VCR cooling system is able to maintain sub-ambient water temperatures over a wide range of power and flow rates resulting in notably lower (~15°C) heat source temperatures with overall Coefficient of Performance ranging between around 1 to 4 over the range of heat source powers tested. The ACHE system, albeit producing higher chip temperatures, could do so at significantly lower mechanical power input penalties, achieving overall COPs in the range of 4 to 28.