Numerical modeling of thermal conductivity of air-plasma-sprayed zirconia with different porosity levels

The effective thermal conductivity of a porous ceramic coating depends on porosity and the distribution of pores. Due to these aspects, the structure of a ceramic coating plays an important role in the analysis of heat transfer. In this study, using real microstructural images, effective thermal conductivities of air plasma sprayed (APS) zirconia coatings have been calculated via CFD modeling as well as using Maxwell-Eucken and the EMT models. CFD studies were carried out using FLUENT 6.1.22 code. Samples were produced having five different porosities by changing the coating parameters. The porosities of the samples were in the interval of 9% - 31%. Results obtained from analytical and finite volume methods have been compared to experimental thermal conductivity data given in the literature. The numerically calculated effective thermal conductivities are in good agreement with those determined experimentally. This study demonstrates that CFD analysis can be used to predict the effective thermal conductivity of porous ceramic coatings using real digital images. By virtue of this, the model can be used to obtain preliminary values instead of high cost and time-consuming experiments.