Abstract Various equations for correlating the thermal conductivity of porous ceramic bodies with the porosity are evaluated, using experimental data on alumina, graphite, uranium dioxide, sandstone, silica brick and limestone. Generally, the correlation equations proposed by Austin, Francl and Kingery, and Biancheria are found to be unsatisfactory. The best equation, which correlates extremely well the thermal conductivity of the ceramic bodies with the porosity, is found to be the one proposed by Aivazov and Domashnev: K K 0 = 1 − P 1 + nP 2 , where K is the thermal conductivity of a porous ceramic body, K0 that of the pore-free ceramic body, P the volume fraction of the pores, and n a constant. This equation is found to be satisfactory up to at least 74% porosity and in the temperature range where the effect of emissivity can be neglected (below approximately 500°C for high-emissivity ceramics).
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