Transient effects of radiative transfer in semitransparent materials

Abstract

Temperature distributions within semitransparent materials can be strongly affected by internal emission, absorption and scattering of radiant thermal energy. This is important for translucent materials at elevated temperatures, in high temperature surroundings, or with large incident radiation. Transient behavior must be examined since translucence can result in internal temperature responses that are much more rapid and have different distributions than by heat conduction alone. Radiation effects on transients have been studied less than for steady state because of additional mathematical and computational complexities, but an appreciable literature has gradually developed. Detailed transient solutions are necessary to examine heat transfer and thermal stresses in ceramic components, ceramic thermal protection coatings, forming and tempering of glass windows, porous burners and insulation systems, energy dissipation from liquid drop and liquid sheet space radiators, some high temperature ceramic components in advanced aircraft engines, and other scientific and engineering applications. In this article, some of the governing equations are summarized along with the required radiative and convective boundary conditions. The literature is reviewed to provide an overview of the computational methods, geometries and types of conditions that have been analyzed. Analytical results are given to demonstrate transient effects and comparisons are made with transient experimental measurements.