Mehdi Bahiraei

This study attempts to evaluate the flow, heat transfer and second law characteristics of a hybrid nanofluid containing graphene–silver nanoparticles inside two new microchannel heat sinks. The temperature dependent thermophysical properties are employed in the simulations. Because the flow is divided uniformly between the channels of heat sinks, a rather uniform temperature distribution is obtained on the heating surface. By increasing either velocity or concentration at both heat sinks, the surface temperature reduces; the cooling uniformity improves; and the maximum temperature also decreases which reduces the possibility of hot spot formation. Moreover, increase of the velocity or concentration intensifies the pumping power in both heat sinks. Figure of merit, i.e. the ratio of heat transfer enhancement to pressure drop increment in the case of using the nanofluid instead of pure water, shows a greater value for the heat sink with more path changes. The results reveal that the heat transfer has a greater contribution in the entropy generation compared to the friction. Moreover, greater fraction of thermal entropy generated in the heat sinks occurs in the fluid part. Based on the results obtained, it is found that employing the heat sink with more path changes and also using the nanofluid as heat transfer fluid can be promising options to be utilized in electronics cooling regarding both first and second laws of thermodynamics.