1G and Microgravity Tank Self-Pressurization: Experiments and CFD Model Validations across Ra and Bo Regimes

Abstract

In this paper several important thermal management aspects of propellant storage tanks are investigated. Special attention is devoted to the heat and mass transport, fluid flow and phase change phenomena that govern tank pressurization and pressure control under 1G and microgravity conditions in terms of three computational-experimental case studies. In the first study, 1G pressurization of a simulant low-boiling point fluid in a small scale transparent tank is considered in the context of the Zero-Boil-Off Tank (ZBOT) Experiment. It is shown that computational predictions of tank pressure and temperature evolution for this moderate Ra and high Bo number regimes are in excellent temporal and spatial agreement with their experimental counterparts. Next, 1G pressurization and pressure control of the large-scale K-site liquid hydrogen tank experiment is considered where the high Bo number - high Ra number flow regimes challenge our ability to predict the vapor phase turbulent heat and mass transfer and their impact on the tank pressurization correctly. Finally, we examine pressurization results from the small scale simulant fluid Tank Pressure Control Experiment (TCPE) and ZBOT Experiment, both performed in microgravity, to show that we have a fairly good ability to simulate the tank self-pressurization rates for low Bo number low Ra regimes encountered in reduced gravity. Unfortunately these results also indicate that accurate tank heat loss and precise knowledge of low and high frequency residual accelerations are all necessary for proper and direct quantitative model validation against microgravity data.