Thermal performance of porous microchannel heat sink: Effects of enlarging channel outlet

The effects of enlarging the channel outlet on the heat transfer through a porous microchannel heat sink (MCHS) were investigated numerically. Emphasis was placed on the influences of the enlargement ratios for the channel outlet width and height on the hydraulic and thermal performances of a porous MCHS. The simulation results indicated that increasing the width or height enlargement ratio reduces the pressure drop across an MCHS. The averaged Nusselt number, heat transfer efficacy, and temperature control effectiveness are enhanced, while thermal resistance is reduced with an enlarged channel outlet. Hence, increasing the width or height enlargement ratio of the channel outlet is an effective method for improving the hydraulic and thermal performance of porous MCHSs. For certain width or height enlargement ratios, the thermal resistance of a porous MCHS is not necessarily lower than that of an MCHS without a porous medium if the pumping power is not large enough to overcome the pressure loss.