Radiation Effects on Heat Transfer in the Reactor Core and Heat Exchangers of an HTGR

Abstract

A general and fundamental study of the effect of radiation between duct walls on the heat transfer performance of duct flows of nonradiating gas such as helium is made by an approximate analysis and numerical calculations. Laminar and turbulent flows in a duct simulating a coolant passage in an HTGR and flows in counterflow and parallel-flow heat exchangers in an HTGR heat transfer system are investigated. An approximate analytical solution, based on the assumption that radiation from a point of duct wall produces an effect only on the narrow region opposite the point, agrees well with numerical results. The increase of radiative heat transfer causes a decrease of temperature difference between the duct walls and improves the heat transfer performance. For heat exchangers the heat transfer effectiveness is shown to depend on three nondimensional parameters and can be improved by the increase of these parameters.