Method to evaluate heat leakage of vertical cryogenic vessels at different liquid levels

Heat leakage from cryogenic vessels is an important parameter of thermal insulation performance reflected by product loss in the standard method. Current standards require the cryogenic vessel to be full before testing, which wastes a considerable amount of working medium. If product loss is tested at another liquid level, especially at a low liquid level, the working medium can be significantly saved, but the results of the product loss test are inconsistent and do not reflect the thermal insulation performance correctly. In this study, the heat leakage of the test product loss was analyzed, and the energy equations of the gas and liquid in the cryogenic vessels were established. Based on these equations, the heat leakage absorbed by the product loss can be divided into two parts: latent heat and enthalpy rise. However, enthalpy rise is ignored in the standard method; therefore, the product losses are inconsistent at different liquid levels. The heat leakages were then calculated and compensated by the enthalpy rise at different liquid levels. These heat leakage results are consistent and their errors are below 5.0 %.