Phase-change transpiration cooling in heterogeneous composite porous plates: Heat transfer characteristics and their prediction

•A novel heterogeneous pore model was developed for composite porous structures.•Cooling efficiencies with heterogeneous composites are inferior compared to metals.•The pore structure and conductivity influenced cooling efficiency significantly.•Improving pore uniformity and permeability can enhance the cooling effect. Ceramic matrix composites are lightweight, high-temperature resistant materials that are extensively utilized in aerospace applications. Transpiration cooling with porous ceramic matrix composites is regarded as one of the most efficient thermal protection methods for spacecraft vehicles exposed to high heat fluxes. However, the feasibility and mechanism of phase-change transpiration cooling in heterogeneous ceramic matrix composite pore structures still remain unclear. In this study, the effect of phase-change transpiration cooling on heterogeneous C/C-SiC porous plates was investigated. A novel heterogeneous pore model based on micro-CT scanning slices was developed, which increased the accuracy of the transpiration cooling simulation with composite materials, and provided accurate flow distribution and phase change process inside the porous media. Experiments were conducted in a wind tunnel with a Mach number of 3 and a total temperature ranging from 450 to 550 K. Results of simulations and experiments demonstrated that the transpiration cooling effect with phase change of ceramic matrix composites is significant. In the future, the pore uniformity and permeability of ceramic matrix composites should be improved to enhance the cooling efficiency. By combining high-temperature-resistance composites with high-performance phase-change transpiration cooling, lighter thermal protection solutions for extreme heat environments can be achieved.