Investigation of thermal contact conductance of bare copper-copper and aluminum 1070-aluminum 1070 interfaces at low temperatures between 10 and 70 K

Abstract

The prediction model of thermal contact conductance (TCC) for bare OFHC-OFHC and Al 1070-Al 1070 flat interfaces is presented. OFHC (Oxygen free high conductivity copper) and Aluminum are widely used in cryogenic systems. Since the thermal conductivity of pure copper or aluminum materials has a highly non-linear characteristic with its peak value at around 20 K, it is difficult to predict TCC of those materials at this temperature range. The TCC model in this paper proposes the dimensionless correlation through 16 experiments considering various conditions such as surface roughness, materials, pressure, and temperature. The model has been established by the modification on the previous CMY (Cooper, Mikic, Yovanovich) model with additional parameters. The first important feature of the model is to adopt the contact thermal conductivity (kc). It can be calculated by using the size effect theory at the micro-scale contact single spot. The second feature is the dimensionless temperature (T/TD). An experimental setup is constructed inside of the conduction-cooled cryostat to measure the thermal conductivity of bulk material and the TCC simultaneously for the temperature range between 10 K and 70 K. OFHC and Al 1070 specimens with various surface roughness are prepared and tested with contact pressure of 6 to 13.5 MPa in vacuum environment. The predicted TCC by the proposed model shows a reasonable agreement with the experimental results in low temperature.