Thermal wave analysis for measurements of thermal diffusivity

An experimental temperature oscillation technique is described for the thermal diffusivity. By periodic sinusoidally modulated laser beam a temperature oscillation is generated at a spot or line of the thin specimen. The temperature oscillation at the heated spot/line results in a wavelike propagation behavior of heat flow and temperature within the specimen. With increasing distance this thermal wave is strongly attenuated and phase-shifted. The characteristic of thermal wave propagation depends directly on the thermal diffusivity of the specimen. So the thermal diffusivity can be calculated from the attenuation of amplitude as well as from the phase lag of the thermal wave. For monitoring thermal waves an infrared line scanner is used, which allows a non contacting real time measurement of temperature distributions. Experiments are carried out to confirm the practical applicability. Measured thermal diffusivities of copper, paper, polycarbon, and aluminum agree well with data from the literature