Optimum design of microchannel heat sinks

Abstract

Analyses have been performed to obtain momentum and thermal characteristics in microchannel heat sinks. The applicability of existing correlations for friction factor and Nusselt number is investigated. The study revealed that existing correlations based on the analytical results can predict the heat sink performance to within the accuracy limits acceptable for use in design. A user friendly computer code has been developed as an aid in the optimum design of microchannel heat sinks. The program, using thermal resistance models, operates in two modes, In mode one, the performance capabilities, power requirements and efficiencies of an existing heat sink design are evaluated. Mode two is used as a design tool for heat sink optimization. In this mode, given the overall heat sink geometry, fluid and substrate properties, and inlet and outlet boundary conditions, the program determines the optimum channel spacing and fin thickness. Implementation of the optimization scheme is presented and its effectiveness is evaluated. Improvements of up to 45% in heat transfer rates are observed by analyzing thermal resistance surface plots for wide ranges of fin thickness and channel spacing. In addition, the idea of designing heat sinks for turbulent conditions rather than laminar are examined. The results show that significant reductions in the total thermal resistance are not achieved by designing for turbulent flow. In contrast, significantly higher pumping power requirements are realized when designing for turbulent flow with only slight improvement in overall thermal performance