临近空间环境下封闭方腔内耦合换热特性

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。 

Conjugate heat transfer characteristics of enclosure cavity in near space environment

Aimed at the application of near space aerostats'load cabins,numerical simulation of natural convection,surface thermal radiation and heat conduction in a cubical enclosure cavity with a heat source in complex thermal boundary conditions was carried out.A model of near-space thermal environment was estab-lished considering the effects of convective heat transfer,infrared radiation and solar radiation.The diurnal variation of the thermal characteristics in the enclosure cavity was studied by introducing the external unsteady convection-radiation coupling thermal boundary conditions through the Fluent software's user-defined function (UDF).The effects of solid wall thickness,emissivity and thermal conductivity were discussed.The numeri-cal results indicate that the average temperature change in the enclosure cavity is about 12.9 K during one day,and the temperature field distribution changes with the sun's position.The natural convection in the en-closure cavity is weak and the maximum temperature difference is 71.3 K at the same time.Increased thermal resistance and surface emissivity lead to weakening of natural convection in the cavity.