Acquiring the thermal conductivity of anisotropic insulating materials accurately has important implications for applications of insulation materials. In this study, a modified step-wise transient method with special considerations of heat-loss effect occurring at the edge of measured samples, finite geometry of the sample and orthotropic thermal conductivity was proposed. A three-dimensional model in a rectangular coordinate system was established to describe the heat transfer process correctly. A general analytical solution of the temperature rises of the measured sample was derived by applying Laplace-transform technique and the separation of variables method. It is indicated that the temperatures calculated by the analytical solution agree well with the results of numerical calculation. The sensitivity analysis of crucial parameters was performed to select appropriate measuring points of the measured sample. Based on the above analysis, the orthotropic thermal conductivities of the measured anisotropic materials were achieved by measuring the temperature rises at two points of the measured sample. The simulation results demonstrate the reliability and validity of the proposed model taking orthotropic thermal parameters, heat-loss effect and finite geometry of the sample into account.
A Study on the Heat Loss Effect of Steel Structure in a Refrigerator Mullion
