The influence of wall properties on convective heat transfer in isothermal nanochannel

Abstract

The effect of solid wall properties on the convective heat transfer characteristic in a three-dimensional nanochannel is probed with molecular dynamics simulation. The interfacial velocity slip and temperature jump are treated as the function of the interatomic interaction, the atomic mass and thickness, respectively. The result shows that the wall properties, including interatomic interaction among wall atoms, atomic mass, as well as coating thickness based on certain interatomic interaction and atomic mass, will lead to significant changes in the temperature jump. These effects are caused by the variations of coupling degree of solid-liquid vibration frequency induced by the mismatch between solid wall and fluid atoms. Furthermore, temperature jump is also related to the solid-liquid interaction while the velocity slip is only related to the solid-liquid interaction. It's found that both the decrease of interatomic interaction and the increase of atomic mass can further enhance the heat transfer. That is, the interatomic interaction among wall atoms is closer to that among fluid atoms, the atomic mass of wall atoms is much greater than that of the fluid atoms, and the convective heat transfer in the channel is better. However, the variation of Nusselt number with coating thickness is notably, which exhibits a peak value in the hydrophilic and hydrophobic cases. It's indicated that vibrational density of states (VDOS) corresponding to a selected coating wall properties (including interatomic interaction, atomic mass and thickness) lies in between the VDOS of the channel wall atoms and that of fluid atoms, can play a role of thermal bridge between wall and fluid atoms and lead to a remarkable increase of heat transfer. Based on the selected solid wall properties, a reasonable selection of wall-fluid interaction can effectively increase velocity slip and achieve drag reduction.