Phonon transmission theory of heat transfer through solid–gas interfaces

The heat flow is investigated from a hot solid into a gaseous medium using the phonon transmission theory. This basic approach correctly predicts the essential features of the temperature jump occurring at solid–gas interfaces during heat flow across the boundary and the predictions agree well with recent measurements of heat transfer between microspheres of UO2 in helium and nitrogen atmospheres. The results suggest that the medium–medium acoustic mismatch dominates the heat transfer through these interfaces.