Thermal conductance at solid interfaces: an application of the Fenech-Rohsenow model

Abstract

An analysis of the thermal conductance of 240 pairs of uranium dioxide-Zircaloy-4 contact is presented. The analysis uses the Fenech-Rohsenow (F-R) model and the surface profiles obtained from mass-produced UO 2 pellets and Zircaloy cladding used in nuclear reactor fuel assemblies. For no contact pressure the differences in surface finish and the relative position of the surfaces in contact give a wide range of thermal contact conductance from 1.14 to 3.60 W cm −2 °C −1 in a helium environment. The contact conductance is insensitive to contact pressure up to 0.7 MPa apparent pressure. The values of the thermal conductance increase rapidly beyond that pressure due to the plastic flow of the Zircaloy-4 surface asperities. Values of thermal contact conductance evaluated with the Ross and Stoute (R-S) correlation are higher than those obtained with the F-R correlation. This difference is attributed to the use of average fluid thickness in the R-S correlation.