Study on the heat transfer performance of stepped lap joint in thermal protection tile based on carbon foam

The heat flow through the slit between the thermal protection tiles (TPT) may cause fatal damage to the structure of spacecraft. In this study, a stepped lap joint for tiles based on coal-based carbon foam was designed to investigate the heat transfer near the slit. A pore scale stochastic model of coal-based carbon foam was developed, and the anisotropy of geometry and thermal conductivity were analysed with steady-state heat transfer method, as well as their relation. The anisotropic conductivity of foam was then used in a 2D numerical model of tiles, and the heat transfer in the lap region of the joint was analysed with transient heat transfer method. Heat transfer experiments of tiles were conducted. The thermal insulation performance of the lap joint improved about 8.6 % and 10.2 % from that of slit inclination angle α = 90° to those of α = 56° and 124° respectively, due to the more tortuous heat transfer path and the larger region affected. The performance improvement was 11.2 % by filling with the SiO₂ aerogel in the slit, mainly contributed by those in the transverse direction. This study could provide a reference for the design of stepped lap joints of thermal protection tiles.