Heat transfer enhancement in microchannel heat sinks with periodic expansion-constriction cross-sections

The heat transfer enhancement of microchannel heat sinks with periodic expansion-constriction cross-sections is investigated both experimentally and numerically. Each heat sink consists of 10 parallel microchannels with 0.1 mm wide and 0.2 mm deep in constant cross-section segment and each microchannel consists of an array of periodic expansion-constriction cross-sections. Three-dimensional laminar numerical simulations, based on the Navier-Stokes equations and energy equation, are obtained for pressure drop and heat transfer in these microchannel heat sinks under the same experimental conditions. Multi-channel effect, entrance effect, conjugate heat transfer, viscous heating and temperature dependent properties are considered. It is found that the numerical predictions of apparent friction factor and Nusselt number are in good agreement with experimental data. The influences of periodic expansion-constriction cross sections on pressure drop, heat transfer and thermal resistance are discussed, respectively. The effects of the entrance and exit plenum regions and the lateral parts of silicon wafer on fluid flow and heat transfer are discussed. Special attentions are given to analyze the variation of thermal resistance for each term with pumping power, corresponding to three stages of heat release at the substrate of heat sink.