A new data reduction procedure in the flash method of measuring thermal diffusivity

Abstract

This article presents a new way to reduce data in the flash method of measuring thermal diffusivity. Experimental temperature versus time data are first periodized, then transformed by using the discrete Fourier transformation (DFT), and the real part of the second term of the transformed temperature is then fitted with a theoretical formula derived in this article. The main advantage of this procedure is that the thermal diffusivity calculation actually does not depend on the temperature level before the flash, and can also be applied in the case when the measured temperature signal of the sample is superimposed with an arbitrary linearly rising or falling signal, with no need to know the parameters of this imposed signal. This is a unique, completely new feature of this procedure, which has no analog among the other methods of data reduction. Practically, it means that the thermal diffusivity of the sample can be measured by the flash method under an arbitrary dynamically (linearly) changing condition of temperature. The proposed procedure allows the treatment of perturbed signals, even in the case when the data are partly statistically correlated, i.e., the noise is not Gaussian. Experimentally, the data reduction procedure has been tested for a correction of the effect of an electronic noise imposed on the temperature versus time signal in the flash method. The results show that the reproducibility of our procedure is favorable, and the accuracy is comparable with other data reduction methods.