A new method for evaluating the heat leak of cryogenic vessels without exhaust gas.

The thermal insulation performance of cryogenic vessels is evaluated by the boil-off gas (BOG) rate and heat leak as a reference standard; however, it consumes considerable testing time and working medium. In this study, we proposed a method of evaluating the thermal insulation performance of cryogenic vessels from the heat leak in the self-pressurization process, which can minimize the testing time and preserve the working medium. To improve the accuracy of heat leak calculation, the vapor temperature distribution of cryogenic vessels is analyzed and considered in the calculation of heat leak. However, it is ignored in the current standard test method. In this study, the energy equations of cryogenic vessels in the self-pressurization process were established by considering the vapor temperature distribution. Then, based on the experimental data, the heat leak was calculated for demonstrating the thermal insulation performance of cryogenic vessels depending on the new method. The results indicate that the vapor temperature should be seriously considered when the liquid level ratio is less than 50 %.