Experimental investigation of transpiration cooling through porous ceramics using hydrogen

In order to investigate porous ceramics transpiration cooling performance and potentials using hydrogen as coolant at high pressure and high heat flux, a model chamber was designed and fabricated by reaction bonded SiC with radial directed pore by freeze-casting, which has well oriented pore structure green bodies obtained from a slurry. All the tests were executed in an air arc-heater. Totally 13 hot tests were carried out with 10~28% media porosity, at 3.6~7.9MPa chamber pressure and blowing ratio about 0.008~0.021. The results indicate a significant reduction of heat transfer rate through porous ceramics by hydrogen transpiration cooling. For a blowing ratio of 1%, the local heat transfer coefficient was reduced by about 30% relative to the heat transfer coefficient with no blowing. Some empirical correlations are modified.