Measurement of the thermal properties of materials by the hot plate method considering the convection coefficient around the device

Abstract

Measurement methods based on the hot plate did not consider the exchange coefficients around the device. These measurements were based on analytical solutions of the unidirectional (1D) heat conduction equation. This paper describes an experimental method to simultaneously estimate the thermal conductivity and thermal diffusivity of materials, taking into account the exchange coefficient around the device. This method is based on the measurement of the temperature at the center of a heating element inserted between two samples, with the unheated surface of the samples being kept constant. As a first step, a two-dimensional (2D) heat transfer model was solved using the finite volume method (FVM) and implemented in MATLAB®. To validate the computational code developed with the 2D model, a comparative study was performed with the full 3D model simulated in COMSOL Multiphysics. This 2D model was then used to perform a sensitivity analysis on the different thermophysical parameters and the convection coefficient. The Levenberg-Marquardt algorithm was used to calculate the estimates. An experimental study was performed on several material samples, leading to an estimation of their thermal properties. In addition, a comparative study based on the asymmetric hot plate (AHP) method was performed, and the results obtained showed a relative error of less than 4%. Therefore, it can be concluded that the proposed model is validated to provide reliable thermophysical properties of materials.