Radial two-phase thermal conductivity of ceramic sponges up to high temperatures - experimental results and correlation

The experimental determination of the radial two-phase thermal conductivity with forced convection (often also called effective thermal conductivity) at high temperatures up to 1100 K for different ceramic sponges (variation of material, porosity and cell size) is presented. The experimental results are shown and dependencies are clarified. The sponges investigated were made of alumina, mullite, oxidic-bonded silicon carbide (OBSiC) and silicon infiltrated silicon carbide (SiSiC). They have porosities between 75% and 88% and cell densities in the range of 10 ppi to 30 ppi. Due to the high temperature domain, the thermal radiation is significant and cannot be neglected. The radial two-phase thermal conductivity under forced convection conditions is highly dependent on the superficial air velocity, the temperature, the porosity and the cell size of the sponge sample. Furthermore, for future prediction of the radial two-phase thermal conductivity of sponges, a correlation based on an approach summing up the different underlying heat transfer mechanisms is developed.