Overall thermal diffusivity of materials using a 3D cartesian model. Effect of sample geometry on the measurements

In this work, we analyse the influence of the sample shape on the experimental determination of the thermal diffusivity of materials used in several engineering fields. By means of a simple method we obtain good estimations of the overall thermal diffusivity for homogeneous or inhomogeneous materials. The method is based on the combination of simple temperature measurements with the analytical solution of the 3D differential Fourier’s equation applied to cartesian geometry. The classical transient analytical solution based on the separation of space and time variables is adapted to particular thermal boundary conditions. By associating these solutions with the measurements obtained on a simple experimental bench, the thermal characterization of materials can be achieved with a satisfactory precision. The present 3D study attempts to complete previous works dealing with cartesian and cylindrical 1D and 2D models. Based on the same procedure, it sheds further light on the fast multidimensional surface phenomena of heat exchange. Although we conclude that the 3D model does not provide the directional values typical of anisotropic materials, our results revealed that thermal diffusivity can be useful in other respects, being advantageous in the overall thermal characterization needed for sizing certain systems.