Prediction of Thermal Conductance of Metallic Surfaces in Contact

Abstract

A mathematical analysis of a thermal contact is first carried out on an idealized shape of contact point. The thermal conductance is expressed in terms of the thermal conductivities of the metals and of the fluid filling the voids, the real area in contact, the number of contact points per unit area, and the volume average thickness of the void gaps. A method is given for the determination of the above physical properties of a contact. To use this method the following measurements are needed: Two recorded profiles, perpendicular to one another; and a Knoop hardness test on the softer of the two metals making the contact. The last part of the paper is devoted to the experimental verification of the assumptions made in the theoretical analysis and to the application of the method outlined for the case of an iron-aluminum contact. Good agreement was found between the predicted and measured conductance over a range of pressures from 90 to 2600 psi.