Sub-cell radiation-conduction (SCRC) model in densely packed beds of mono-sized pebbles for HTGR under vacuum condition

Abstract

The equivalent sub-cells of radiation and conduction are modeled for close packing structures of mono-sized pebbles. The aim is to calculate and analyze the average radiative and conductive heat transfer of high-temperature gas-cooled reactors (HTGRs) under different ranges of temperature to further assist in the design and operation of HTGRs. The sub-cell radiation-conduction (SCRC) model is established analytically according to the analysis of thermal resistance networks for radiation and conduction. It can be utilized to calculate the effective thermal conductivity (ETC) due to radiation and conduction in an HTGR under vacuum conditions. Comparisons of data of ETC obtained from the SCRC model, empirical models, and experiments are carried out under vacuum conditions. Comparisons of the non-dimensional radiation exchange factor (REF) between the SCRC model and other occasionally used models are also given. The comparisons show that the SCRC model is generally in accord with the commonly used models and the experimental results. The results demonstrated that the established SCRC model is expected to be able to describe the radiation and conduction in closely packed pebble beds under wide temperature ranges and vacuum conditions reasonably.