Thermal Contact Resistance of Nonconforming Rough Surfaces, Part 2: Thermal Model

Abstract

A new analytical model is developed for thermal contact resistance (TCR) of nonconforming rough surfaces. TCR is considered as the superposition of macro- and microthermal resistances. The effects of roughness, load, and radius of curvature on TCR are investigated. It is shown that there is a value of surface roughness that minimizes the TCR for a fixed load and geometry. Simple correlations for determining TCR, using relationships introduced in Part 1 of this study, are derived that cover the entire range of TCR from conforming rough to smooth spherical contacts. With introduction of an approximate model, it is shown that the effective microthermal resistance is not a function of surface curvature and contact pressure profile. The comparison of the present model with 600 experimental data points shows good agreement in the entire range of TCR. A criterion for conforming contacts is proposed that gives a range for the ratio of out-of-flatness to surface roughness.