Effect of thermal radiation on the effective thermal conductivity of open-cell SiC foams
Charles C. Tseng, Triplicane A. Parthasarathy, Ruth L. Sikorski, Raymond Viskanta and Ming Y. Chen
To use open-cell foam materials for high temperature applications, thermal radiation may be important or dominate heat transfer in foams; however, the effective thermal conductivity which is one of the most important thermal characteristics of foams is difficult to estimate due to the fact that studies based on detailed thermal radiation analysis are limited. In this paper foams are considered to be semitransparent, because radiation can penetrate through the pore (or void) space and/or foam skeleton (ligament), depending on the materials from which the foams are made. Of particular interest in this study is to create a model that includes the effect of the foam physical properties (such as its density, mean cell size, etc.) on the conductive and the radiative transfer through silicon carbide (SiC) foams for predicting the temperature dependent effective thermal conductivity. In the paper, the dimensionless strut diameter is considered to be an important physical parameter of foams. The attenuation/extinction behavior of SiC foams is considered to be a function of the dimensionless strut diameter of the foam. The results reveal that the foam physical properties can significantly reduce the effective thermal conductivity of the foam used for the thermal protection.
Keywords: Open-cell foams, silicon carbide, high temperature, effective thermal conductivity, thermal radiation, thermal protection.