Detailed and simplified models for evaluation of effective thermal conductivity of open-cell porous foams at high temperatures in presence of thermal radiation

Simulations of coupled conduction-radiation heat transfer through open-cell porous foams have been performed in this article in order to evaluate the effective thermal conductivity (ETC) at high temperatures due to combined effects. For this purpose, the complex structure of foams has been generated using the knowledge obtained from 3D Computer Tomography (CT)-scan images and both detailed and simplified homogeneous modes have been employed during the present investigation. For detailed models, in addition to the energy conservation equation, the radiative transfer equation has been solved in order to obtain the distribution of radiation intensity using the blocked-off region approach, which can handle the voxel information acquired from the CT-scan data. Proposed simplified models, on the other hand, are based on homogenization approach and the performance of these simplified models has been compared with the reference model in terms of their accuracy. Simplified models mainly require information about the ETC due to pure conduction calculated from detailed 3D simulation and the extinction coefficient estimated from the CT-scan data using the image processing technique. Extensive parametric study has been conducted and the analysis of results show that ETCs estimated from the simplified models reasonably agree with those obtained from the most accurate model, depending upon the chosen value of extinction coefficient. (C) 2013 Elsevier Ltd. All rights reserved.