Performance study on thermodynamic vent system in cryogenic propellant tank

The thermodynamic vent system (TVS) is crucial for the long-duration storage of cryogenic propellants in spacecraft, involving various instruments and complex processes of phase changes and heat transfer. This paper summarises the background research and existing works, developing theoretical models for cryogenic propellant tanks and throttling refrigeration valves. Using AMESim software, simulation models of the TVS system were constructed and analysed, leading to the proposal of different venting schemes: gas throttling, liquid throttling and multi-cycle mixing methods. The performance of these methods was analysed based on venting flow and cooling rates, with simulation results validated by ground test data. Key parameters, such as nitrogen flow rate, exhaust gas temperature and nitrogen tank pressure, were detailed. The findings indicate that gas throttling outperforms liquid throttling in cryogenic propellant conservation, while the combination of gas throttling and multi-cycle mixing optimises pressure control in the propellant tank.