Investigation on engineering applications of cryogenic pipeline chill-down.

Cryogenic pipeline chill-down, involving intricate interaction of phase change, heat transfer and multiphase fluid dynamics, is an indispensable process for cryogenic devices, including in-space cryogenic engines, inspace fuel storage depots and ground filling systems. However, there is a big gap between theoretical analysis and practical engineering operation due to the unclear chill-down characteristics and complex composition of the actual filling system. Thus, in the present paper, more cryogenic two-phase investigations, standing in the view of engineering applications, are conducted for achieving the safe and high-efficiency management of cryogenic propellants. The results show that the special characteristic resulted from transient flow regime
transition would promote the two-phase instability and an optimal mass flow rate exists to reduce the chilldown time. Besides, due to the higher sensible heat of hydrogen gas, single gas forced convection contributes significantly to chill-down process, accounting for about 74% of total heat exchange.