Cryogenic two-phase natural circulation loop.

• Cryogenic natural circulation loop analyzed experimentally and mathematically. • The circulation flow-rate calculated by the two-phase flow model: HEM and TEDFM. • The TEDFM estimated the circulation flow rate with 5% error. • The two-phase flow pattern of cryogenic liquid verified with flow visualization. This paper presents the application of cryogenic natural circulation loop for engine cooling of launch vehicles, and the experimental measurements of the natural circulation system. The experimental results indicate that the circulation flow rate increases with an increase in heat input and a decrease in system pressure, on varying them. The study includes the temperature and pressure profiles of the natural circulation loop. The steady-state flow rate calculation was developed with two-phase models: the homogeneous equilibrium model (HEM) and thermal equilibrium drift-flux model (TEDFM). The TEDFM revealed a 5% error in the experimental circulation flow rate, and it is agreeable with the experimental results. The small-scale experimental setup verified the two-phase flow pattern in the cryogenic natural circulation loop. A fully liquid flow was observed in the downward section. The horizontal section had a bubbly flow, where the speed of the gas and liquid were similar. The slug and churn flows were present in the vertically upward section, where gas velocities were faster than liquid. Both HEM and TEDFM can be applied in the horizontal heated section. However, it is more appropriate to apply TEDFM in the vertically upward section during the pressure drop calculation for the cryogenic natural circulation loop. [ABSTRACT FROM AUTHOR]