Radiant heating experiment using stand-off Thermal Protection systems with diffuse reflection based on Mie theory

Abstract

Diffuse reflection of thermal radiation transfer by Mie scattering can provide a thermal barrier without conversion leading to conduction heat transfer. Applying such a system to internal thermal insulating materials of a stand-off thermal protection systems (TPS) provides an efficient means of preventing thermal radiation transfer. Porous MgAl₂O₄ ceramics have high thermal resistance and low emissivity. For this study, the heat transfer between the porous MgAl₂O₄ ceramics and the fibrous insulator was evaluated using the Lambert-Beer rule and the Fourie rule in a vacuum infrared lamp system for the radiation heating layer (Layer-1) and the back layer (Layer-2) to investigate the effect of the decrease in apparent heat transfer coefficient. The effect of using a low-emissivity material for the radiation heating surface and a low thermal conductivity layer for the second layer was confirmed to be more effective in reducing the apparent thermal conductivity than when a single material was used. It is suggested that the low emissivity layer on the radiation heating surface not only suppresses the heat input of the radiation but also suppresses the heat transfer in the thickness direction.