Numerical investigations on the effect of fin shape and surface roughness on hydrothermal characteristics of slip flows in microchannels with pin fins

Abstract

Accurate modelling of convective heat transfer in micro/nano gas flows is critical for many applications such as temperature/mass flow micro-sensors and mixing/separation analysis of gases in micro-systems. This study numerically investigates the effect of pin fin shape and wall roughness on heat transfer and flow field of gas flows in rough microchannels in the presence of the second order slip boundary condition. The hydrothermal characteristics of flows were obtained for a smooth microchannel under slip boundary conditions for the constant wall temperature (330 K) and constant wall heat flux (10 kW/m2) boundary conditions. Afterwards, four types of pin fin shapes (rectangular, diamond, oblong, and elliptic) and two types of surface roughness (regular and random rough elements) were taken into account. According to the obtained results, although velocity slip raises Nusselt number, temperature jump tends to reduce it. It was shown that the generated recirculating flows between the roughness elements reduce Nusselt number and increase friction factor. Furthermore; it was found that the effect of pin fin shape diminishes with surface roughness.