Forced Convective Boiling in Microchannels for kW/cm² Electronics Cooling

This paper reports some of the results of our tests for the development of a high heat flux cooling system for thermal management of high power electronics. Our objective is to develop a practical design solution for achieving 1000 W/cm² cooling. To achieve such high heat transfer rates, we have pursued and combined design advantages of a microchannel heat exchanger, high heat fluxes associated with forced convective nucleate boiling, and the use of a nanoparticles laden fluid for enhancement of heat transfer. A laboratory test module was designed, built, and tested to verify its performance. The experimental system employed sub-cooled as well as saturated forced convection boiling heat transfer in a high aspect ratio parallel microchannel heat sink. The working fluids tested were water and a selection of ceramic-based nanoparticle suspensions (nanofluids). The system was observed to readily dissipate heat fluxes in excess of 275 W/cm² of substrate, while maintaining the substrate at or below 125°C. For optimized fin geometry, the current conditions would result in greater than 500 W/cm². While the use of nanofluids was intended for boiling enhancement to push the envelop beyond 1000 W/cm², we discerned limited improvement in the overall heat transfer rate. Future studies are planned for further exploitation of nanoparticles for enhancement of convective nucleate boiling.