Two-Dimensional Effects on Measurement of Thermal Diffusivity by AC Calorimetric Method: I. Conditions for Precise Measurement

In the application of an ac calorimetric method to precise thermal diffusivity measurement of a thin material, one-dimensional temperature wave propagation is required. In a relatively thick material, one-dimensional temperature wave propagation is deformed and in the strict sense, two-dimensional temperature wave propagation should be taken into account. In the present paper, we propose the condition of the maximum thickness of a material required to measure thermal diffusivity within an accuracy of ±2% in the framework of one-dimensional temperature wave propagation, based upon the results obtained analytically for the two-dimensional temperature wave propagation.