Microchannel heat sink with designed roughness: Analysis and optimization

A microchannel heat sink with rib structures is investigated numerically for thermal resistance and pumping power. Multi-objective shape optimization of a staggered-rib microchannel heat sink is performed using a multiobjective evolutionary algorithm. Three design variables (Le., ratios of the rib height to width of channel, width to height of the rib, and channel width to pitch of the rib) are selected for optimization. Thermal resistance and pumping power are taken as objective functions. Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved for flow analyses using a finite volume solver. Thermal resistance is decreased and the Nusselt number is increased at the expense of pressure drop in a ribbed microchannel. Thermal resistance in a ribbed channel is generally higher than that in a smooth channel for fixed pumping power, but the difference in thermal resistance reduces as pumping power increases. The design variable of the ratio of rib height to width of channel is primarily responsible for and the most sensitive to the heat transfer augmentation, whereas ratios of width to height of the rib and channel width to pitch of the rib are found to be less sensitive in the design space. The ratio of channel width to pitch of the rib is found to be the most Pareto-sensitive (sensitive along the Pareto-optimal front), whereas the ratio of width to height of the rib is found to be the least Pareto-sensitive.