The thermal conductivity of perlite insulation under varying conditions of temperature, humidity and packing denisty

Measurements have been made of the thermal conductivity of expanded perlite under varying conditions of density and humidity over the temperature range 113 K to 298 K. A thermal conductivity test cell was constructed according to the requirements of ASTM C177. The measurement system and test methods are described. The new test data shows that perlite conditioned in standard conditions has a thermal conductivity of 0.0153 to 0.0193 W/mK at 113 K. Varying the relative humidity (R.H) of the environmental chamber used to prepare some samples from 40% to 80%, made little to no change to the thermal conductivity values. However, increasing the density of the perlite packed into the cavity of test cell, by 15% to 25% resulted in moderate increases in the thermal conductivity at the maximum density of 2.0% and 7.7% and was dependent on the source.