漫射和准直光束辐射对自然对流对称冷却情形的影响
Effects of Diffuse and Collimated Beam Radiation on a Symmetrical Cooling Case of Natural Convection
摘要：
本文用数值方法研究了漫射辐射和准直辐射对底部加热的二维空腔内自然对流对称冷却的影响。腔体底部对流加热，换热系数为50 W/m2 K，自由流温度为305 K，腔体两垂直壁面均为等温，温度为296 K。顶壁是绝热的，并且所有壁对于辐射热传递是不透明的。对于准直的情况，在左壁上已经创建了高度为0.7的无量纲宽度为0.05的小半透明窗口，并且在该半透明窗口上以角度45施加值为1000 W/m2的准直照射。结果表明，漫辐射对腔内两辊的动力学特性影响不大，而准直光束的照射则显著改变了腔内两辊的动力学特性，同时也改变了腔内的换热特性。这进一步随着流体的光学厚度而变化。在透明流体中，准直光束的左涡旋比右涡旋大，而在非零光学厚度的流体中，准直光束的左涡旋比右涡旋大。
英文摘要：
In the present work, the effects of diffuse and collimated radiation on the symmetrical cooling case of natural convection in a two-dimensional cavity heated from the bottom have been investigated, numerically. The cavity is convectively heated from the bottom with heat transfer coefficient of 50 W/m2K and free stream temperature 305 K, while both vertical walls of cavity are isothermal at temperature of 296 K. The top wall is adiabatic and all walls are opaque for radiation heat transfer. For collimated case, a small semitransparent window of non-dimensional width of 0.05 at height of 0.7 has been created on the left wall and a collimated irradiation of value 1000 W/m2 at an angle 45 is applied on this semitransparent window. The results reveal that the diffuse radiation has little effect on the dynamics of two rolls inside the cavity, however, collimated beam irradiation changes the dynamics of two rolls significantly and also the heat transfer characteristics. This further changes with the optical thickness of the fluid. The left vortex is bigger in size than the right vortex for collimated beam in transparent fluid, whereas, reverse trend is seen for collimated beam in non-zero optical thickness of the fluid.
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