Development of thermal stratification in a rotating cryogenic liquid hydrogen tank

• Thermal stratification in rotating liquid hydrogen tank is investigated.
• The influences of spin rate, tank aspect ratio and gravity level are analyzed.
• Interface phase change has caused great effects on fluid thermal stratification.

Accurate prediction of thermal stratification in cryogenic propellant container is of significance to space missions. In the present paper, a thermal stratification model, considering phase change transmission at the liquid vapor interface, is developed and adopted to investigate the pressurization performance and stratification development in a rotating liquid hydrogen tank. Heat exchange associated with viscous flow is particularly considered to ensure that the flow and heat exchange are continuous when Ra is in the range of 0.1 to 1015. The calculated results show that the stratified layer in a rotating tank develops more slowly than in a non-rotating tank. With the rotation rate increasing from 1.0 deg/s to 4.0 deg/s, the required time of stratification developing fully has increased approximately 1.82 times. The speed of the stratification development with aspect ratio of 0.5 is approximately 2.27 times faster than that with aspect ratio of 1.0. The fluid stratification under different gravity levels express different developing speed, slower developing speed is observed at the micro-gravities. More than 10 times consumed time needs to reach fully field stratification at 10−4g0 comparing at 1g0. Meanwhile the ullage pressure increases faster with the greater gravity level. It is also found that the liquid–vapor phase change has great influence on the tank pressure. The deviation of ullage pressure increased reaches by 18.27% with the consideration of phase change. It is suggested that phase change effect should be accounted for in the prediction of thermal stratification and ullage pressure of liquid hydrogen tank.