Extraction of thermal contact conductance of metal-metal contacts from scale-resolved direct numerical simulation

The thermal contact conductance (TCC) between two conforming metallic rough surfaces was extracted from scale-resolved direct numerical simulation (DNS) of thermal transport across the interface. To compute thermal transport across the interface, microscale models of the interface geometry were created by stochastically reconstructing the topography of the two metallic surfaces, followed by generation of meshes that resolved all fine-scale features of the interface, including the air pockets. Steady state conjugate heat conduction computations were then conducted, and the TCC values were extracted and expressed as a function of the applied pressure (which translates into a mean separation distance) and the mean interface temperature. When compared with experimental data, the extracted TCC values were found to be in good agreement, thereby validating the approach. To lend practical value to the methodology and data presented in this paper, a relationship was also established between the extracted TCC and the number of contacts between the two surfaces. Further, it was shown that the number of contacts generated using surface reconstruction (numerically computed) correlates well with the theoretically calculated number of contacts using the joint probability distributions of the asperity heights on the two surfaces. The implication of these relationships is that irrespective of the actual topography of the surface, for a given pressure (separation distance) and metallic pair combination, the TCC can be estimated from the correlations presented in this paper (TCC versus number of contacts) without the need to conduct any additional numerical computations.