Heat Transfer Characteristics for Gaseous Flow in Long Rectangular Microchannels

摘要

Heat transfer characteristics for compressible flow in microchannels were less studied both experimentally and numerically. Experimentally, it was due to the difficulties in fabricating micro temperature sensors. Numerically, it was due to the long computational time and large memory required in simulating the full Navicr-Stokes equations three-dimensionally. This study develops an efficient three-dimensional numerical procedure to investigate heat transfer characteristics of steady compressible laminar flow in long microchannels. The proposed numerical procedure solves the reduced compressible Navier-Stokes equations. Two boundary conditions, a constant wall heat flux and an isothermal wall, were simulated in this study. The local Nusselt number in microchannel flows subject to a constant wall heat flux diminishes considerably along the channel axis. The effect of heat flux on the friction characteristic of microchannel flows was also examined. The effect of pressure ratio on the local Nusselt number was investigated. The local Nusselt number in microchannel flows subject to an isothermal wall was found to behave quite differently compared with that of conventional channel flows. The reasons for the differences were explored and discussed.