Performance enhancement in double-layer tapered microchannels by changing the wall hydrophobicity and working fluid

Due to the acceptable performance of microchannel heat sinks in electronic components, their performance enhancement in repelling the high heat fluxes has received much attention. In this research, the effects of applying the hybrid nanofluid flows in a double-layer microchannel heat sink with superhydrophobic walls are investigated numerically. The finite volume method is used to perform numerical simulations of the 3D solid-liquid conjugate model. The conventional straight microchannel containing pure water is considered as the base case and the aim is to increase the thermohydraulic performance of these channels by using hybrid nanofluid, converging channels, and superhydrophobic surfaces. The results indicate that at low Re numbers, the thermal resistance of the hybrid nanofluid in the superhydrophobic microchannel (in all values of tapered factor) is lower than that of the conventional microchannel with pure water. However, at high Re numbers, the situation is reversed. This is due to the higher temperature jumps at the wall contact surfaces for high Re numbers. Also, the excessive pumping power caused by the nanoparticles for volume fractions less than 3% can be compensated with superhydrophobic surfaces.