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以临近空间浮空器载荷舱为应用背景,对复杂热边界条件下含热源的三维封闭方腔内自然对流、表面辐射和导热的耦合问题进行了数值模拟。综合考虑对流换热、长波辐射、太阳辐射等因素的影响,建立了临近空间热环境模型。通过Fluent软件用户自定义函数(UDF)引入外部非定常的辐射-对流耦合热边界条件,对腔内换热特性的昼夜变化进行研究,并分析了腔壁厚度、发射率和导热系数对其的影响。数值结果表明,腔内平均温度昼夜变化很小,约为12.9 K,但温度场分布随太阳方位变化而变化;腔内对流换热较弱,同一时刻最大温差约为71.3 K;腔壁热阻和发射率增加会削弱自然对流的强度。
In this paper, the numerical simulation of the coupled problem of natural convection, surface radiation and thermal conductivity in a three-dimensional enclosed cavity with heat source under the condition of complex thermal boundary is carried out with the loading space near space aerostat. Considering the influence of convective heat transfer, longwave radiation and solar radiation, the thermal environment model near space is established. The Fluent software user-defined function (UDF) was used to introduce the external non-stationary radiation-convection thermal boundary conditions and to study the diurnal variation of the heat transfer characteristics in the cavity. The influence of cavity wall thickness, emissivity and thermal conductivity influences. The numerical results show that the average intracavity temperature changes very little, about 12.9 K, but the distribution of the temperature field changes with the azimuth of the sun. The convective heat transfer in the cavity is weak and the maximum temperature difference at the same time is about 71.3 K. And the increase of emissivity will weaken the intensity of natural convection.