Thermal conductivity dependence of MgO thermal insulation on in temperature range 500-2000 K

Thermal conductivity of MgO (magnesia) foam thermal insulation with porosity 0.49-0.81 have been measured by the non-steady plane flow method in the temperature range of 500-2000 K at atmospheric pressure. We have demonstrated a significant influence of porosity on the apparent thermal conductivity of MgO insulating materials in the temperature range 500-1500 K. Materials with porosities exceeding 0.75, have relatively low radiation attenuation coefficients. This results in a relatively large contribution to the radiative component of the apparent thermal conductivity. For such materials this property measured at temperatures above 1700 K weakly depends on porosity. The measured apparent thermal conductivities are analyzed on the basis of a theoretical model, accounting for total material porosity and particle size distribution. We discuss the suitability of the data on particle and pore size distributions, measurable by various experimental methods, for calculation of the apparent thermal conductivity.