Conductive-radiative heat transfer within SiC-based cellular ceramics at high-temperatures: A discrete-scale finite element analysis

Abstract

Cellular ceramic materials possess many favorable properties that allow to develop efficient modern-day high-temperature thermal energy conversion systems and processes. The energy conversion within these porous media is governed by tightly coupled conduction–radiation physics. To efficiently design and optimize these systems, a comprehensive understanding of the conduction–radiation behavior within these materials becomes important. In this study, by performing large-scale numerical experiments, we analyze the conduction–radiation coupling characteristics within different (with respect to topology and porosity) silicon carbide (SiC)-based open-cell cellular ceramics surrounded by fictitious vacuum up to temperatures of 1800 K. To induct minimal approximations, our finite element simulations are based on a discrete-scale approach within which realistic discrete (pore-level) representations of the cellular ceramics are used as numerical media. The results presented in this study provide means to better understand the role of radiation in the coupled conduction–radiation physics within the ceramic samples. A detailed comparison on effectiveness of energy conversion is established for SiC-based full-scale cubic-cell, Kelvin-cell, and pseudo-random-cell ceramic structures which are at 80% and 90% porosity each. In conclusion, among the different standalone and full-scale ceramic samples, the Kelvin-cell structures at 90% porosity have proven to benefit the most from radiation coupling.