Estimating the thermal contact conductance of metals by ultrasonic waves

Abstract

Experiments and numerical simulations were performed to study heat transfer through a contact interface between two metallic solids in order to clarify the effects of roughness and waviness of the contact surface on the mean thermal contact conductance hm. In the experiments, the characteristics of an ultrasonic transmission were also investigated so as to obtain a relation between hm and the transmitted sound energy ratio, with and without attenuation, at the contact interface Er. Ten pairs of brass specimens were tested in an atmospheric environment at room temperature. Each specimen was a cylindrical block 40 mm in diameter and 45 mm long. The contact surface was finished by polishing, grinding, milling, or turning. Mean nominal contact pressures pm from 0.08 to 1.67 MPa were applied to the test columns. Our analysis takes account of the radial distribution of thermal contact conductance, using numerical solutions of the two-dimensional cylindrical heat conduction equation to simulate the heat transfer experiments. From the simulations, the effects of roughness and waviness on the temperature fields around the contact surfaces and on hm were clarified. Finally, for flat rough surfaces, an empirical correlation expression between hm and Er is proposed. Using this expression, hm can be predicted to within about ±50%. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(2): 130–141, 1998