Heat and Mass Transfer Modeling of Vacuum Insulated Vessel Storing Cryogenic Liquid in Loss of Vacuum Accident

Cryogenic liquid is often stored in a vacuum insulated Dewar vessel for a high efficiency of thermal insulation. Multi-layer insulation (MLI) can be further applied in the double-walled vacuum space to reduce the heat transfer from the environment to the stored cryogenic fluid. However, in loss-of-vacuum accident (LOVA) scenarios, heat flux across the MLI will raise to orders of magnitudes larger than with an intact vacuum shield. The cryogenic liquid will boil intensively and pressurize the vessel due to the heat ingress. The pressurization endangers the integrity of the vessel and poses an extra catastrophic risk if the vapor is flammable, e.g., hydrogen. Therefore, safety valves have to be designed and installed appropriately, to make sure the pressure is limited to acceptable levels. In this work, the dynamic process of the heat and mass transfers in the LOVA scenarios is studied theoretically. The mass deposition - desublimation of gaseous nitrogen on cryogenic surfaces is modeled, as it provides the dominant contribution of the thermal load to the cryogenic fluid. The conventional heat convection and radiation are modeled too, although they play only secondary roles, as realized in the course of the study. The temperature dependent thermal properties of e.g., gaseous and solid nitrogen and stainless steel are used to improve the accuracy of calculation in the cryogenic temperature range. Presented methodology enabling the computation of thermodynamic parameters in the cryogenic storage system during LOVA scenarios provides further support for the future risk assessment and safety system design.