Abstract
To implement image-based numerical modeling of the thermal conductivity of coatings, a YSZ coating was considered as a network of two phases, namely the coating material and pores. The variation of the thermal conductivity of the gas trapped within the pores caused by their small size was considered by complying with the Knudsen law. In the present work, the quantification of the Knudsen effect on the effective thermal conductivity of coatings was achieved with the help of image analysis. The thicknesses of the pores were determined by combining the use of the Scion image software with a new in-house algorithm coded in C language. The Knudsen effect was quantified by applying a finite-difference model for both 2D images and a 3D image. In both cases, a decrease of the computed thermal conductivity was found while considering the Knudsen effect. Furthermore, the Knudsen effect was also taken into account in a finite-element model applied on the same images. Despite differences were noticed on the computed thermal conductivities obtained with the two methods, a quite similar decrease was calculated by comparing with data computed with the FDM method.