Effects of Surface Wettability and Roughness on the Heat Transfer Performance of Fluid Flowing through Microchannels

The surface characteristics, such as wettability and roughness, play an important role in heat transfer performance in the field of microfluidic flow. In this paper, the process of a hot liquid flowing through a microchannel with cold walls, which possesses different surface wettabilities and microstructures, is simulated by a transient double-distribution function (DDF) two-phase thermal lattice Boltzmann BGK (LBGK) model. The Shan-Chen multiphase LBGK model is used to describe the flow field and the independent distribution function is introduced to solve the temperature field. The simulation results show that the roughness of the channel wall improves the heat transfer, no matter what the surface wettability is. These simulations reveal that the heat exchange characteristics are directly related to the flow behavior. For the smooth-superhydrophobic-surface flow, a gas film forms that acts as an insulating layer since the thermal conductivity of the gas is relatively small in comparison to that of a liquid. In case of the rough-superhydrophobic-surface flow, the vortex motion of the gas within the grooves significantly enhances the heat exchange between the fluid and wall.