Thermal Conductivity Measurements on High-Temperature Fibrous Insulations by the Hot-Wire Method

Abstract

We have developed equipment to determine the “thermal conductivity” of insulating materials, in the temperature range 25° to 1600°C, by the hot-wire method. We have based our method on the German draft standard DIN 51046 and on the work of Padgett and Davis at the British Ceramic Research Association (BCRA). The method has been applied to measurements on polycrystalline alumina fibers, where the “thermal conductivities” range from 0.03 to 0.8 W/m-K. This paper gives details of our experiences with the hot-wire method and indicates some areas where we have found difficulties that are not completely covered in the specification. In order to assess the value of “thermal conductivity” data obtained by the hot-wire method, we have, where possible, tried to compare our results with those obtained by parallel-plate methods. The dangers of making such a comparison are indicated, but the agreement between the results obtained by the two different methods gives us confidence in their reliability for insulation design.