Abstract 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.

中文翻译：

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低温两相自然循环回路

摘要 本文介绍了低温自然循环回路在运载火箭发动机冷却中的应用，以及自然循环系统的实验测量。实验结果表明，循环流量随着热输入的增加和系统压力的降低而增加。该研究包括自然循环回路的温度和压力分布。稳态流速计算是用两相模型开发的：均质平衡模型 (HEM) 和热平衡漂移通量模型 (TEDFM)。TEDFM 显示实验循环流量有 5% 的误差，与实验结果一致。小规模实验装置验证了低温自然循环回路中的两相流动模式。在向下部分观察到完全液体流动。水平段有气泡流动，气体和液体的速度相似。段塞流和搅动流出现在垂直向上的部分，其中气体速度比液体速度快。HEM 和 TEDFM 均可应用于水平加热段。然而，在低温自然循环回路的压降计算过程中，在垂直向上部分应用TEDFM更为合适。