Thermohydraulic performance of winglets inside a rectangular microchannel

For application chaotic advection in microchannel heat sinks, manipulation of extended structures (longitudinal vortex generators) is done to increase the conjugate heat transfer by disrupting the boundary layer. A Microchannel heat sink (MCHS) with rectangular winglets was etched on an externally heated silicon substrate and deionized water was used as the working fluid. A comprehensive parametric study was done to analyze the effects of winglet height, angle, and various staggered configurations. The thermal enhancement was evaluated by augmenting the Nusselt number (Nu) and friction factor. The common flow-up configuration (CFU) had higher helicity and vortex index which resulted in higher thermal enhancement. The optimum height of the winglet was 0.75 times the channel height. As the winglet angle increases, frictional loss increases with a marginal gain in convective heat transfer. As winglet length increases, the optimal winglet angle shifts from 30° to 45°. The staggered CFU configurations resulted in higher heat transfer and lower frictional loss in comparison to conventional CFU and common flow-down (CFD) configurations. For the CFU stagger configuration, Nu is 32.8 and overall the overall thermal enhancement is 2.5 (Reynolds number 1050). The validity of the vortex index for the heat transfer study is also established.