Thermal gap conductance - Effects of gas pressure and mechanical load

Nitrogen and helium gap-conductance data are reported for interfaces formed by contacting bead-blasted/ lapped stainless-steel type 304 and nickel 200 pairs over a range of gas and contact pressures at a fixed mean interface temperature of about 440 K. The effective interface surface parameters are controlled by the beadblasted surface roughness and mean absolute asperity slope. The effective contact microhardness is controlled by the Vickers microhardness layer of the lapped surface and the effective interface surface parameters. The data show the rarefaction, transition, and continuum heat-conduction regimes at gas pressures from about 10-760 Torr. The predictions of several gap-conductance models are compared against the data. Significant differences between the predictions of some of the models and the data are reported. The models of Veziroglu and Yovanovich are in good to very good agreement with the data.