垂直矩形通道内的混合对流实验与数值研究

Experimental and Numerical Studies on Mixed Convection in Vertical Rectangular Channels

对耦合了热辐射的垂直矩形通道内的混合对流情况进行了实验研究和数值模拟分析。研究表明:空气在通道内向上流动时,随着浮升力作用的增大,对流换热能力表现出先减小后增强的趋势;热辐射在换热过程中起着重要的作用,并随着对流换热能力的减弱而增强。数值模拟在浮升力影响较小时可以给出较好的结果,当浮升力影响比较大时,数值模拟计算的结果与实验有较大的偏差。

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.