Retrieving thermal conductivities of isotropic and orthotropic materials

This paper describes the development of a novel non-destructive technique to measure the thermal conductivity (TC) of isotropic and orthotropic materials. The sample is locally heated using a laser flash, and the spatial and temporal changes of the temperature field are recorded using an IR camera that is located on the same sample side as the energy source. The TC is then measured by invoking an inverse technique that is based on the best fit of the recorded and modelled spatial temperature distribution within the sample by applying computational fluid dynamics (CFD). The solution to the resulting mathematical model encompasses both the sample and the surrounding air and was obtained using a commercial CFD solver. The values of the TC tensor were determined by minimizing the discrepancy between the modelled and measured temperature using the Levenberg-Marquardt technique. The determined TC was compared with that obtained by the classic Parker flash method. This work is an initial step towards the development of a measurement method that can be used to determine the thermal conductivity of engine blades and thin coatings with arbitrary shapes without sample preparation. The developed numerical model exhibits good accuracy in comparison with other measurement techniques.