Thermophysical Characterization of Earthen Materials Using the Flash Method

Abstract

This work deals with the analytical solution of the rise temperature history on the back face of the unfired clay bricks related to the theoretical model of flash method, was calculated using Duhamel theorem. The local sensitivity analysis of the obtained solution shown that the sensitivity coefficients related to the thermal diffusivity and the adiabatic limit temperature meets the beck criterion for low time range, so these tow parameters can be simultaneously estimated with a good accuracy in this time range. Due to the slow convergence of the analytical solution in short times, the procedure for estimating the thermophysical properties is relatively slow. The theoretical analytical solution has therefore been replaced by an equivalent solution whose convergence speed was improved using the Wynn Epsilon method. The apparent thermal diffusivity and the adiabatic limit temperature of samples were then estimated by fitting measured rise temperature with the equivalent analytical solution. It is interesting to note the good agreement between the theoretical model with predicted values of parameters and the experimental data.