Investigation on heat transfer during transpiration cooling with hydrocarbon fuel coolant

•The thermal dispersion of the fluid is enhanced with cracking reaction.•A non-thermal equilibrium model is used to study the cracking reaction.•The ratio of chemical heat sink to physical heat sink is studied.•The change of heat transfer coefficient due to cracking reaction is studied. The article presents a numerical approach to investigate the transpiration cooling problems with coolant cracking reaction inside porous media. The effects of cracking reaction, coolant mass flow rate per unit area, coolant inlet temperature and heat flux distribution on porous wall on the transpiration cooling are studied. Studies have shown that the cracking reaction of hydrocarbon fuels can greatly improve the heat absorption caused by only physical heat sink, and the heat sink ratio can exceed 1 near the outlet of the porous media. The cracking reaction can improve the solid temperature uniformity of porous media at the inlet, but has a negative impact on that at the outlet, and the temperature difference between the fluid and the solid increases at the outlet of the porous media because the small molecular products produced by the cracking have a smaller specific heat capacity. The occurrence of the cracking reaction reduces the flow Reynolds number of the fluid inside the porous media, and the convective heat transfer coefficient is limited. Small-molecule products from cracking enhance thermal dispersion inside porous media, which is conducive to the transfer of local high heat to the surrounding area and reduces thermal stress.