Most surface properties used in calculating contact conductance are not intrinsic to the surface, but vary with the sampling frequency of the instrument used to characterize the surface. This paper offers a methodology for characterizing a surface based on intrinsic surface characterization properties (the self-affine fractal dimension and topothesy), intrinsic material properties, and applied load. A surface characterization model is developed to predict the wavelengths on a surface that are significant in predicting thermal contact conductance. The surface characterization model is combined with surface deformation and constriction resistance models to predict contact conductance across nominally flat, metallic surfaces. The long-wavelength cutoff in the surface characterization is set by the dimensions of the contact area. A theoretical correlation for the short-wavelength cutoff as a function of surface and material properties and load is developed, and then improved by a least-squares fit to experimental data. The integrated model developed predicts contact conductance in three modules: defining unique asperity geometries important in deformation modeling; calculating the mode of asperity deformation; and accounting for the actual geometry of asperities in the constriction resistance model. The predicted contact conductance compares well to experimental data over a range of surface roughnesses, pressures, and substrate materials.

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A. F. Black and S. V. Garimella, “Characterization of Rough Engineering Surfaces for Use in Thermal Contact Conductance Modeling,” AIAA Journal of Thermophysics and Heat Transfer Vol. 20(4), pp. 817-824, 2006.