Effect of rib shape and fillet radius on thermal-hydrodynamic performance of microchannel heat sinks: A CFD study

New designs for ribbed microchannels (semi-circular and semi-elliptic) and filleted ribs are numerically studied in the present paper. Four presented configurations include: microchannel with semi-circular ribs (MC-SCR), microchannel with semi-elliptic ribs (MC-SER), microchannel with semi-circular ribs and filleted corner (MCSCR-FR) and microchannel with semi-elliptic ribs and filleted corner (MC-SER-FR). Thermal and hydraulic performance of these configurations are evaluated by comparing Nusselt number, fanning friction factor, and performance evaluation criteria (PEG). Based on the results, the ribs corner curvature leads to a significant increase in heat transfer coefficient, accompanied by a minor increase in pressure drop. Compared to MC-SCR and MC-SER heat sinks, the two designs of MC-SCR-FR and MC-SER-FR enhance Nusselt number about 18-21% and 0.5-10%, increase the fanning friction factor about 0.1-7% and 1-9%, and improve the performance evaluation criteria (PEG) about 19-22% and 19-21%, respectively. In addition, because of the re-development of thermal boundary layer and higher mixing level, MC-SCR-FR configuration revealed the best performance among all other configurations. Moreover, the effect of relative fillet radius on thermal-hydrodynamic performance of MC-SER-FR configuration is investigated, and R* > 1.2 is selected as the appropriate value for design of microchannel heat sinks.