Abstract To study the droplet entrainment mechanisms in liquid nitrogen (LN2) and vaporous nitrogen (VN2) countercurrent flow, simulation on three fields comprised of the liquid, the vapor, and the droplet phase was implemented for the horizontal segregated flow based on the Eulerian-Eulerian mathematical framework in ANSYS Fluent®. The droplet entrainment model was adopted to determine the droplet entrainment and deposition source terms, and the position of the generated droplet was also estimated by calculating the velocity gradient in the normal direction of the interface toward the gas core. The model was validated according to the available data of water–air flow in the literature. For further evaluation of the model applied in the cryogenic fluid, the experiment and simulation of LN2-VN2 countercurrent flow were performed in a horizontal pipe of 15 mm diameter and 900 mm long. Three flow patterns, including stratified-wavy flow, churn flow, and pseudo-slug flow, were visually identified. The characteristics of the three flow patterns were obtained through the comparison of simulated contour results and experimental video recording. Furthermore, ligament breakup was found to be the main droplet entrainment mechanism in the churn and pseudo-slug flow. Pressure drop signals of the three flow patterns were also obtained and analyzed.

中文翻译：

---

考虑液滴夹带的液氮和气态氮逆流研究

摘要 为了研究液氮 (LN2) 和气态氮 (VN2) 逆流中液滴的夹带机理，基于欧拉方程对水平分离流进行液、气、液滴三场模拟。 ANSYS Fluent® 中的欧拉数学框架。采用液滴夹带模型确定液滴夹带和沉积源项，并通过计算界面法向朝向气核的速度梯度来估计产生的液滴的位置。根据文献中现有的水-空气流数据对模型进行了验证。为了进一步评估应用于低温流体的模型，LN2-VN2逆流实验和模拟在直径15mm、长900mm的水平管中进行。三种流动模式，包括分层波浪流、搅动流和伪段塞流，通过视觉识别。通过模拟轮廓结果和实验视频记录的比较，获得了三种流动模式的特征。此外，发现韧带断裂是搅动和伪段塞流中的主要液滴夹带机制。还获得并分析了三种流动模式的压降信号。通过模拟轮廓结果和实验视频记录的比较，获得了三种流动模式的特征。此外，发现韧带断裂是搅动和伪段塞流中的主要液滴夹带机制。还获得并分析了三种流动模式的压降信号。通过模拟轮廓结果和实验视频记录的比较，获得了三种流动模式的特征。此外，发现韧带断裂是搅动和伪段塞流中的主要液滴夹带机制。还获得并分析了三种流动模式的压降信号。