SUMMARY

The International Technology Roadmap for Semiconductors (ITRS) predicts that microprocessor power consumption will continue to increase in the foreseeable future. It is also well known that microprocessor performance can be improved by lowering the junction temperature: recent analytical studies show that for a power limited chip, there is a non-linear scaling effect that offers a 4.3X performance enhancement at -100 °C, compared to 85 °C operation. Vapor Compression Refrigeration (VCR) is a sufficiently compact, low cost, and power efficient technology for reducing the junction temperature of microprocessors below ambient, while removing very high heat fluxes via phase change. The current study includes an experimental investigation of small-scale, two-stage cascaded VCR systems, and a scaling analysis of single- and multiple-stage VCR systems for electronics cooling. In the experimental work, a two-stage cascaded VCR system is demonstrated that can remove 40 W/cm2 at -61 °C, at a size of about 60000 cm3. In the scaling analysis, a method for estimating the size of single- and multiple-stage VCR systems is described, and the resulting trends are presented. The compressor and air-cooled condenser are shown to be by far the largest components of the system, dwarfing the evaporator, expansion device, and inter-stage heat exchanger. For systems utilizing off-the-shelf components and removing up to 200 W of dissipated power at evaporator temperatures as low as 173 K, compressor size dominates the system and scales with the compressor’s motor. The air-cooled condenser is the second largest component, and its size is constrained by the air-side heat transfer coefficient.