Determination of Thermal Diffusivity by the Temperature Wave Method

An analysis has been made on the Angstrom's method to determine the thermal diffusivity of solids when the size of the specimens are comparatively small. The equation of thermal conduction was solved under boundary conditions that the temperature was varied sinusoidally at one end of the specimen and was constant at the other end connected to a heat sink. The solution shows that there exist temperature waves propagating along the specimen, attenuating gradually, and being vanished completely at the end connected to the sink. Expressions to determine the thermal diffusivity by measuring the attenuation or the phase difference of the waves at two positions along the specimen have been derived. An apparatus to determine the thermal diffusivity of N-type germanium has been measured at room temperature. The experimental results showed a good agreement with those computed numerically using the present analysis.