Thermodynamic analysis of partially filled hydrogen tanks in a wide scale range

The primary challenge for the long-term storage of cryogens in space is evaporation and consequent pressurization due to heat leakage. This study innovatively presents the scale effects on pressurization covering a wide range of tank volume from 6.37 x 10(-3) to 208 m(3), under normal gravity and microgravity. A computational fluid dynamic model based on the volume-of-fluid method is constructed to predict the thermodynamic behaviors in partially filled hydrogen tanks. The geometric scale is found to play a significant role in influencing the pressurization rate only for tanks in the small-scale range, especially under normal gravity. The pressurization rate is lower under microgravity than under normal gravity for small tanks. However, the opposite is observed when the tank size exceeds a critical value. An empirical correlation is originally presented to relate the real pressurization rate to the tank diameter and the pressurization rate based on homogeneous model. According to a thermodynamic analysis, the direct sensible energy input of vapor, the mass transfer on the liquid-vapor interface, and the liquid thermal expansion are the three causes of self-pressurization, which are all related to the geometric scale. The conclusions can be used for the pressurization prediction of various emissions in the aerospace applications.

Automated summary

The study investigates the effects of scale on pressurization in cryogen storage tanks in space, finding that geometric scale only significantly influences pressurization rate in small-scale tanks. The causes of self-pressurization during the pressurization process are related to geometric scale, including direct sensible energy input of vapor, mass transfer on the liquid-vapor interface, and liquid thermal expansion. The findings can be utilized for pressurization prediction in various aerospace applications.