Second law analysis of hybrid nanofluid flow in a microchannel heat sink integrated with ribs and secondary channels for utilization in miniature thermal devices

Abstract

A second law assessment is conducted to study irreversibility values for the stream of a hybrid water-based nanofluid within a microchannel heat sink fitted with secondary channels and rectangular ribs. The hybrid nanofluid has been synthesized from the graphene nanoplatelets on which the silver nanoparticles have been decorated. In the fluid part, entropy generations caused by heat transfer and friction are intense in the interfaces of solid-fluid, whereas lower thermal entropy generation occurs in the dead zones. In the solid part, thermal entropy generation in corners of the solid-fluid interface is higher than other regions. The lowest thermal entropy generation happens at the front of ribs, whereas the frictional entropy generation demonstrates lowest values at the heat sink central part. With the elevation of either Reynolds number (Re) or weight fraction, the entropy produced by heat exchange reduces. A 7 % decline in the total entropy generation happens by adding the nanoparticles with concentration of 0.1 % at Re = 300, while a 17 % reduction in this parameter happens with elevating the Re from 100 to 500 at concentration of 0.06 %. Furthermore, with the growth of concentration and decrement of Re, the contribution of solid to thermal entropy generation intensifies compared with the fluid.