Modeling of Pressure Reducing in a Cryogenic Tank by a Thermodynamic Vent System Considering Flashing

Thermodynamic vent system (TVS) is a promising approach for controlling pressure propellants in cryogenic tanks under microgravity conditions. Prior simulations for the pressurization of cryogen in the tank with TVS basically treated the liquid as quasi-static by the venting operation. However, experiments showed that the liquid could be superheated during that period. The present work will present a model for the passive TVS for one-dimensional cryogenic tanks. Flash evaporation correlation is adopted for calculating the phase change between the superheated liquid and the vapor. The predicted pressure by the model that considers flash evaporation agrees with the experimental data better than that without considering the flashing phenomenon. The evaporation rates in the cases at different fill levels are compared based on the model. It is found that the flashing has a significant impact on the cycle period and mass mean loss rate prediction.