High Flux Heat Removal with Microchannels—A Roadmap of Challenges and Opportunities

Heat fluxes in IC chips and other electronics equipment have reached the current limits of air-cooling technology. Some of the applications require heat fluxes well beyond the limit of 100 W/cm 2 , thus demanding advanced cooling solutions. Liquid cooling technology has also received attention as the advances in single-phase liquid cooling in microchannels have shown considerable promise. The extension of compact heat exchanger technology to microscale applications offers many new possibilities. The liquid cooling technology is expected to reach heat dissipation rates as high as 10 MW/m 2 (1 kW/cm 2 ) with enhanced microchannels and a junction-to-air temperature difference of 50°C. The challenges facing flow boiling systems are also evaluated. This paper reviews the fundamental technological developments in liquid cooling as well as flow boiling and presents possible solutions in integrating the cooling system with a building's HVAC unit in a large server-type application. The opportunities and challenges are described in an attempt to provide the roadmap of cooling technology for cooling high flux devices in the next decade. Acknowledgments The author gratefully acknowledges the IBM Faculty Award in support of his research related to high heat flux heat removal from IC chips using single-phase and two-phase cooling systems.