Thermal performance improvement of microchannel heat sinks by utilizing variable cross-section microchannels filled with porous media

Abstract This study presents optimal design of microchannel heat sinks (MCHSs) by utilizing variable cross-section microchannels filled with porous media to improve the MCHS thermal performance. A parametric optimization has been carried out based on varying coolant passage widths and heights with or without a porous material, regarding two different objectives: an average heat transfer coefficient and pumping power. Results indicate that the coolant passage enlargement has a positive impact on reducing the required pumping power. Although the coolant passage's width enlargement causes a slight drop in the heat transfer coefficient, the coolant passage's height extension provides a higher heat transfer coefficient. In addition, the porous material has a significant effect on reducing pumping power; however, it causes a slight reduction in the heat transfer coefficient. The results reveal that there is an optimum design for MCHS with a porous material. Numerical optimization carried out at Reynolds numbers ranging 140–560, shows better performances at higher Reynolds numbers; however, the effectiveness of utilizing variable cross-section microchannels and porous media are less pronounced when the Reynolds number increases. Utilizing variable cross-section microchannels filled with and without porous media is found to enhance conventional microchannel heat sinks performance up to 90% and 40%, respectively.