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 established 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 numerical 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 enclosure 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.