Thermal conductivity of silica refractories and its temperature dependence during thermal cycling, compared to silicite and sandstone

Abstract

The thermophysical properties of silica refractories are important for their potential application as high-temperature thermal energy storage (HT-TES) media. In this paper, we report new measurements of thermal conductivity and thermal diffusivity by plane-source techniques and the laser-flash technique, respectively. The latter is also used to determine the temperature dependence of the thermal conductivity from room temperature to 800 °C during heating and cooling. It is shown that for a silica refractory with porosity 21 % the experimentally measured thermal conductivity (1.3–1.6 W/mK) is significantly lower than the analytical and numerical predictions for spherical, polyhedral and concave pores (3.1–4.7 W/mK), which indicates the influence of microcracks. The anomaly in the temperature dependence below ∼200 °C can be attributed to the phase transitions of cristobalite and tridymite, but above this temperature the thermal conductivity increases, whereas that of silicite and sandstone decreases. Thermal cycling leads to microcrack-induced damage.