Design and Optimization of Microchannel Cooling Systems

Microchannel heat sinks have been shown to exhibit significant heat transfer rates from extremely small volumes, albeit at the expense of moderately high pumping power. However, their successful integration into commercially viable miniature cooling systems will likely be determined by system-level factors such as energy efficiency, weight, volume, manufacturability, material compatibility, and ultimately, cost. While previous studies have focused on optimizing the microchannel heat sink device in isolation, the present study focuses on the entire system comprising a microchannel heat sink, a pump, a liquid-to-air plate and fin compact heat exchanger, and a fan or blower. A thermal resistance-based network model is constructed to characterize the system physics. Heat transfer and flow parameters for the liquid and air sides, as well as spreading in the microchannel heat sink base, are predicted using correlations from the literature. Heat extraction optimization is linked to heat rejection capability to allow for a holistic approach. Optimal system design with and without manufacturability constraints is presented to quantify the "gap" between ideal and practical solutions. Analysis is carried out for copper microchannel heat sink and heat exchanger materials, with water as the liquid side coolant, and with a commercial pump and fan as fluid moving devices