Numerical simulation study of thermal and hydraulic characteristics of laminar flow in microchannel heat sink with water droplet cavities and different rib columns

Microchannel heat sink is an effective technology to dissipate heat for high flux density devices. However, it is still unknown that what geometric structure form of channel will most effectively improve the overall performance of microchannel heat sinks. Three-dimensional numerical simulations were carried out to investigate the flow and heat transfer characteristics of microchannel heat sinks designed with an innovative combination of water droplet cavities and rib columns. Five different shaped rib columns were considered, including triangular, rectangular, diamond, elliptical and trapezoidal rib columns. A comparative analysis was presented to discuss the performance of these geometric configurations according to average Nusselt number (Nu), friction coefficient (f), entropy production (S-Delta) and overall performance factor (eta). It was found that the combination of water droplet cavities and rib columns can greatly improve the overall performance of microchannel heat sinks due to the full use of the advantage of rib columns to enhance heat transfer with the strengthened fluid flow disturbance and the advantage of cavities to reduce pressure drop with the enlarged flow area. The rib column shape and geometric parameters have significant effect on hydrothermal performance. Furthermore, the microchannel with water droplet cavities and elliptical rib columns has the best overall performance in all the cases and its overall performance factor achieves up to 1.513 with alpha = 0.3 and xi = 0.5 at Re = 331.32.