Use of Computational Fluid Dynamics in the Design and Optimization of Microchannel Heat Exchangers for Microelectronics Cooling

Increasing circuit density and adherence to Moore’s law is driving advanced cooling systems for the next generation microprocessors. One method receiving considerable study is that of microchannel heat exchangers in silicon substrate. These very fine channels in the heat exchanger provide a greatly enhanced convective heat transfer rate and have been shown to be able to meet the demands of the cooling challenge for microprocessors for many generations to come. While the thermal performance has been demonstrated, the design methodology and analysis for fluid structures at this size scale remains difficult. This paper reviews the use of CFD analysis for the design and optimization of microchannel heat exchangers. These results are compared with classical approaches to the same design and demonstrate the need for CFD analysis. Errors using the standard correlations and methods are demonstrated through the results of an optimization study on microchannels. The effects of entrance lengths, spatial variation of the Nusselt number, and temperature dependencies are considered. The literature has widely varying reports on comparisons between experimental results and corresponding theoretical results in microchannel heat exchangers. Experimental validation of the CFD analysis has also been performed and demonstrates that current CFD techniques are actually well suited to heat exchanger designs of this size.