Role of wall-fluid interaction and rough morphology in heat and momentum exchange in nanochannel

Abstract

As an efficient cooling method, the convective heat transfer in nanochannel has been widely utilized in thermal management of various energy systems. However, the effects of surface roughness on velocity slip and flow resistance in nanochannel are still unclear. The effects of rough morphology and wall-fluid interaction on the flow and thermal characteristics in rectangular nanochannel are probed with molecular dynamics method. The results show that nanostructure morphology and wall-fluid interaction induce distinct variations in temperature jump and velocity slip, which further determine the heat and momentum exchange between the channel wall and fluid. Specifically, rough morphology is responsible for the augments of heat transfer and flow resistance, which is derived from limitation on the motion of fluid atoms by the nanostructure grooves in channel. In comparison, the strong wall-fluid interaction brings about the improvement of heat transfer and the increase of flow resistance, which owes to the adsorption enhancement. As the nanostructure free shear ratio increases from 0.1875 to 0.75, the flow resistance increases and heat transfer performance weakens. Yet, the combination of rough morphology and wall-fluid interaction is significant for overall heat transfer performance. The overall heat transfer performance in rough channel with the weak wall-fluid interaction is superior. The Nusselt number in rough channel only decreases by 1.78% while the resistance coefficient reduces by 27.1%. The optimal overall performance is achieved in rough channel with the nanostructure free shear ratio of 0.1875.