Experimental and Numerical Studies on Mixed Convection in Vertical Rectangular Channels

Mixed convection in rectangular channels is frequently encountered in engineering applications.In spite of extensive studies,investigations on mixed convection coupled with thermal radiation are relatively scarce.The present authors carried out the experimental and numerical studies on the mixed convection coupled with thermal radiation in a vertically oriented rectangular channel.The results show that for upward flow in a vertical channel,buoyancy shows a strong effect and leads to a significant decrease（impairment）in heat transfer in the range of small buoyancy number.With increasing buoyancy number,the heat transfer coefficient,compared to that at forced convection conditions,recovers again.This evidence agrees well with previous studies in the open literature.Furthermore,it is concluded that thermal radiation plays an important role in the process of heat transfer,especially in the parameter range,where heat transfer impairment occurs.Numerical simulation using CFD and low Reynolds turbulence models shows reasonable agreement with the experimental data at low Buoyancy number conditions.The deviation between the numerical results and experimental data becomes larger at high Buoyancy number conditions.