Thermal Contact Conductances of Metallic Contacts at Low Loads

Experimental investigations on thermal contact conductances of metallic contacts have been reported here. The studies are restricted to relatively low contact pressure: hardness ratios $(< 0.7 \times 10^{-3})$ where very little data exist. These results have applications in situations like some types of electrical contacts, cooling of electronic components, contacts in instruments and highpower semiconductors. Results show that the behaviour is considerably different from what happens in high-pressure contacts, due to the increased importance of gap fluid conductance at low pressures. This is not the case at higher interface pressures where the dominant mechanism is the solid spot conductance. The study shows that the correlations developed for highpressure cases cannot be used for low-load conditions. The effects of mean interface temperature, interstitial fluid and thermal rectification are also found to be more pronounced than those for high-pressure conditions

Thermal Resistance Across a Copper/Kapton/Copper Interface at Cryogenic Temperatures

The high-{Tc} superconductor current lead heat intercept connection, which is utilized as a thermal intercept to remove the Joule heat from the upper stage lead to a heat sink operating at 50--77 K, consists of a structure where a 152-{micro}m film is sandwiched between two concentric copper cylinders. The material chosen for the insulating film is Kapton MT, a composite film which has a relatively low thermal resistance, but yet a high voltage standoff capability. Here, the measured thermal conductance of a copper/Kapton MT/copper junction in a flat-plate geometry is compared to the results obtained from the actual heat intercept connection. Increasing the contact pressure reduces the thermal resistance to a minimum value determined by the film conduction resistance. A comparison between the resistance of the copper/Kapton MT/copper junction and a copper/G-10/copper junction demonstrates that the Kapton MT layer yields a lower thermal resistance while still providing adequate electrical isolation

Interlaboratory comparison for heat transfer coefficient identification in hot stamping of high strength steels.

The topic of the paper is the identification of the heat transfer coefficient (HTC) in hot stamping of boron steel sheets under conditions very close to the industrial ones. Two approaches followed by one lab in Germany and one lab in Italy are presented for HTC identification, showing the two experimental apparatuses that were set-up to conduct the tests, the procedures developed and applied to identify the HTC. The obtained results are compared in terms of dependence of HTC from the applied contact pressure, the similarities and the differences of the two approaches are outlined and commented