A Transient Technique to Determine Thermal Conductivity and Thermal Contact Resistance of Porous Materials

The application of a transient technique for the measurement of effective thermal conductivity and thermal contact resistance of porous media is discussed. A sensitivity analysis has proven that direct measurement of thermal contact resistance from a single temperature recording is not feasible. It requires the measurement of at least one additional sample with different height. The estimation of effective thermal conductivity is done by solving the inverse heat conduction problem (IHCP). The direct problem is treated analytically by describing the system with a quadrupole formalism in Laplace domain. The inversion procedure was found to be computational expensive. For this reason, the analytical solution of a reference case was obtained and used to validate a finite difference scheme. The indirect problem of the IHCP is solved via the Levenberg-Marquardt algorithm. Preliminary results are shown to demonstrate the method. Future actions consist of calibrating the experimental setup, benchmark with known materials and report uncertainty.