Enhancement in thermo hydraulic performance of radially curved microchannel with secondary flow

Abstract

Microchannel-based cooling methods have been found extremely suitable for compact heat exchangers. High rate of heat extraction is always associated with pressure drop penalty which lowers the overall performance of the device. Heat sinks that would deliver high thermal performance at relatively lower pumping are highly desirable. In the present article, curved microchannels with secondary flow channels are numerically investigated to minimize the pressure loss and enhance the heat transfer simultaneously. Uniform heat flux boundary condition with Reynolds number ranging from 100 to 225 is considered for analysis. Seven models having secondary flow channel orientation angles varying from 30° to 42° are compared with radially curved microchannel (RCMC) having central inlet and horizontal radial outlet arrangement. A greater increase in Nu is observed in the secondary channel with a higher orientation angle, primarily attributed to enhanced fluid mixing. Results revealed a maximum Nusselt number increase of 25.72% for RCMC with secondary flow (RCMCSF) when compared to RCMC with reduction in pressure drop penalty at the same time. At a Reynolds number of 100, the RCMCSF 30D demonstrated the maximum pressure loss reduction, which amounted to 23.91% compared to RCMC. The temperature of the wall in contact with the fluid exhibits a decreasing trend with an increase in Reynolds number (Re). This occurrence is attributed to improved fluid mixing, resulting from higher flow rates. The intensified velocity vectors in the cross-plane contribute to this enhanced mixing and subsequent decline in wall temperature. Reduction in average wall temperature up to 3.43°C is noted for RCMCSF when compared to RCMC. Of all the designs considered, radial curved microchannel with a secondary channel orientation angle of 40° shows enhanced thermal hydraulic performance with performance factor equal to 1.31.