Role of rectification and hysteresis in controlling thermal contact conductance across joints at low temperatures

Abstract

Hysteresis effect on thermal contact conductance due to load cycling is well documented for joints at ambient temperature. However very limited information is available at cryogenic temperature. The thermal cycling of joints to cryogenic temperature is also an unexplored area. In addition, the change in heat flow direction on thermal contact conductance across joints formed by dissimilar materials, which is referred as rectification, is an important parameter in maintaining desired thermal contact conductance across the joints. In the present study, these factors are experimentally evaluated for joints formed by stainless steel, aluminium alloy and titanium alloy over a temperature range of 150 K to 300 K at low interface loading. The present study reveals that the thermal contact conductance at cryogenic temperature is less affected by hysteresis by an average of 8% and 16% with thermal and mechanical loading cycles respectively. However, Rectification effect in thermal contact conductance is prominently observed in bi-metallic joints. More than 60% change in thermal contact conductance is observed with change in direction of heat flow. The study points out that rectification can be effectively utilised for controlling the thermal contact conductance at cryogenic temperature in joints subjected to low contact pressure, where the use of other controlling methods is constrained.