Prediction of high temperature thermal contact conductance considering radiation effects based on fractal theory

Abstract

High temperature thermal contact conductance is a crucial parameter affecting the performance of thermal control and thermal protection systems in many engineering applications under extreme conditions. In this paper, the rough surface of high temperature Inconel 718 alloy (HTA) was characterized and reconstructed based on fractal theory satisfied with a three-dimensional W-M function. The mechanical deformation of contact model was estimated in considering three types of mechanics at the contact points: elastic, elastoplastic, and plastic. The heat transfer between contact surfaces was analyzed account for the conduction of contact points and the radiation between rough surfaces under high temperature conditions. The effects of pressure (0.1–0.6 MPa), temperature (650–1100 K), and fractal parameters on thermal contact conductance were studied through the proposed model. The results show that the contribution of solid conduction and radiation to total thermal contact conductance increases from 45 % to 73 % and from 14 % to 27 % with increasing pressure and temperature, respectively. Also, the thermal contact conductance increases with decreasing and increasing the fractal parameter of D and G, respectively, due to the simulated surface becomes smoother. And the variation tendency is more significant at higher interface pressure. Additionally, the accuracy of the thermal contact resistance prediction model was validated by comparing the predicted results with experimental data.