Review of Models for Thermal Contact Conductance of Metals

Thermal contact conductance is a topic of great relevance to such applications as electronics packaging, satellite thermal control, nuclear reactor cooling, aerodynamic heating of supersonic aircraft and missiles, and turbine and internal combustion engine design. A fundamental problem in this discipline concerns the contact of metals in a vacuum environment for which gap and radiative conductance are negligible and only contact (solid spot) conductance is appreciable. A number of conductance models for metals are compiled and compared to experimental data from the literature. Theoretical models have been developed that accurately predict contact conductance for the two bounding cases of flat, rough surfaces and nonflat (spherical), smooth surfaces. However, these do not agree with most results for arbitrarily nonflat, rough surfaces, those usually obtained from common manufacturing processes. Empirical and semiempirical correlations, although many are developed for nonflat, rough surfaces, also suffer from limited applicability. The few theoretical models for nonflat (spherical), rough surfaces are computationally intensive and are not readily applied to design.