Development and validation of an analytical charge-hold-vent model for cryogenic tank chilldown

To enable future in-space cryogenic fuel depots, efficient methods are required for the tank chilldown and transfer process to minimize the amount of consumed propellant. This paper presents a transient charge-hold-vent (CHV) analytical model which is compared against the single set of liquid hydrogen tank chilldown data. The model solves conservation of mass and energy, uses quasi-unsteady steps in time to simulate natural convection and jet impingement heat transfer, and tracks two-phase fluid thermodynamic properties as the chilldown process evolves. The additional cooling potential made available through a cyclic tank venting process is also calculated in the code. The flexible code can simulate multiple CHV cycles, be used to optimize tank geometry and nozzle location, and provide predictions on the amount of propellant mass used for each cycle. This model compares within 7% of the liquid hydrogen tank chilldown experimental data.