A Computational Study of the Effect of Fill Level During Tank Self-Pressurization and Validation Against Ground-Based K-Site Experiment

It is essential for NASA’s short and long duration missions to be able to accurately predict rates of tank pressure increase when heat leaks into a cryogenic storage tank through insulation, structural support, and tank penetrations. A two-phase CFD model for self-pressurization of a cryogenic storage tank partially filled with liquid hydrogen was developed using the Volume-Of-Fluid approach for modeling two-phase flow, as well as interfacial heat, mass and momentum transfer between the liquid and vapor regions. The CFD model was validated against self-pressurization experiment performed using the K-site flightweight hydrogen storage tank at NASA Glenn Research Center. The model was initially validated against 49% liquid fill level cases. The validation was extended to two more liquid fill levels – 29% and 83%, studied in the experiment. Laminar and turbulent simulations were performed together with conjugate heat transfer analysis for three different fill levels. Results of these simulations for tank pressures and fluid and wall temperatures are compared with the experimental data for the external tank heat loads of 3.5 and 2.0 W/m2 in this paper. Effects of turbulence, as well as liquid fill level, are presented and discussed.