Thermal Diffusivity Measurement Method of Transparent Material sandwiched between opaque plates by Flash Method
2018 Volume 32 Issue 2 Pages 80-87
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2018 Volume 32 Issue 2 Pages 80-87
It has been confirmed that thermal conduction of optical thickness less than 0.1 is approximately composed of diffusive heat transfer and radiative heat transfer between the end faces. It was applied to single layer glass and the thermal diffusivity was measured at high temperature. Since the opaque film at both ends was made of a thin film whose heat capacity and thermal diffusiviry can be neglected, there was a temperature limit where evaporation and diffusion are active. In order to apply this method at a higher temperature, three layer material with an opaque plate on both ends was examined. This 3 layer material temperature equation was obtained in the Laplace space under the radiation loss. Analyzing method of the 2nd layer thermal diffusivity was investigated. First method is a search of a root-mean-square deviation minimum in the Laplace space under the condition that the thermal diffusivity, diathermic coefficient and the Biot number are independent variable (Direct method). Second method is a method to search the minimum under the condition that the theoretical cooling time constant equals to the cooling time constant of the temperature data (Cooling time constant method). It was confirmed that it is possible to determine the thermal diffusivity by both methods.
