The thermal diffusivity of a solid material can be determined using pairs of identi cal specimens prepared for a thermal conductivity determination in a Guarded Hot Plate apparatus (ASTM C-177). Specimens are placed one on top of the other with a temperature sensor between them, and the pair is placed between the heat-sink plates of a Guarded Hot Plate apparatus. The temperature of these plates is varied at a constant rate.
The thermal conductivity, specific heat and density of the material are assumed to be constant over the range of temperature used for the test. For a pair of granite slabs, at a mean temperature of 8°C, the thermal diffusivity is 8.49 × 10-7 m2/s ± 0.02 × 10-7 m2/s.
