The thermal contact conductance (TCC) between two metallic rough surfaces is dictated both by the size and shape of the asperities on the surface. In this study, scale-resolved direct numerical simulation of thermal transport across the interface was conducted to isolate and quantify their effects. The mean roughness height (indicator of asperity size) and the mean absolute slope (indicator of asperity shape) of the asperities — two common surface topography descriptors — were treated as parameters, in addition to the contact pressure. Microscale models of the interface geometry were generated by statistically reconstructing the surface pairs from the aforementioned topography inputs, followed by generation of unstructured meshes that resolved all fine-scale features of the interface, including the air pockets. Steady state conjugate heat conduction computations were conducted, and the TCC values were extracted. The extracted TCC values were found to be in good agreement with experimental measurements. Examination of trends revealed the TCC to be a strong function of asperity size and a weak function of asperity shape. The extracted TCC data was finally reduced and curve-fitted by correlating it to two non-dimensional parameters: the number of contacts and the mean absolute slope. The accuracy of this correlation (curve-fit) was tested, and the TCC values predicted by it were found to be well within the statistical uncertainty of the raw DNS results. The curve-fit represents a simple, yet valuable tool for future researchers to estimate the TCC of metal-metal interfaces of any topography characterized by common topography descriptors.

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