Thermal characteristics of epoxy as a bonding material in a low temperature vessel

One of the main sources of heat leakage in a low temperature vessel is the thermal conduction of the vessel wall between room temperature and the low temperature. The material of the vessel is generally stainless-steel, and it is fabricated by welding. To reduce the amount of the thermal conduction, materials having low thermal conductivity are chosen. Glass fiber reinforced plastic (GFRP) is one of the adequate candidate materials because it has low thermal conductivity and high mechanical strength. We use GFRP pipe instead of stainless-steel pipe, as a neck in a liquid nitrogen vessel (or Dewar). Epoxy, as a bonding material, is inserted between the GFRP neck and the main body of the vessel. Therefore, the thermal characteristics, especially the thermal expansion, are very important because the vessel is cooled and warmed periodically. The experimental results of thermal expansion between room temperature and the low temperature are presented in the paper. Leakage in a vacuum environment is incurred because of different linear thermal expansion coefficients of various materials. The leakage is investigated using a vacuum-level checking method during the thermal cycle. In addition, the amount of boil-off in a low temperature vessel is discussed in terms of the thermal characteristics of the neck’s material.