Thermal performance of nanofluids in a sinusoidal channel with embedded porous region

Inclusion of porous structures in micro-channels enhances heat transfer rates in energy harvesting devices, which signifies as the working fluid becomes a nanofluid. The present study compares the thermal performance of CuO-water, TiO₂-water and graphene-water nanofluids in a sinusoidal channel with a porous insert. The flow and heat transfer characteristics are simulated and the effects of volumetric fraction of nanofluids, Reynolds number (Re), porous insert width, and its permeability on the flow and temperature fields are examined. The findings reveal that CuO-water nanofluid results in higher heat transfer rates than those of other nanofluids considered. Graphene-water nanofluid gives rise to lower performance than that of CuO-water nanofluid in terms of convection heat transfer despite the fact that graphene has higher thermal conductivity than CuO. In this case, a decrease in Nusselt number of as much as 6.34% is observed for CuO-water nanofluid among all the cases considered for the Reynolds number of 100. Increasing the permeability of the porous insert slightly enhances (∼0.24%) the average Nusselt number. The porous insert with a small width in the channel improves the heat transfer rates (2.25% increase in Nusselt number), i.e. the average Nusselt number reduces as the porous insert width increases.