基于OpenFOAM的含不凝气蒸汽气泡冷凝模拟

Numerical Study of Air-vapor Mixture Bubble Condensation in Unsaturated Water Using VOF Model in OpenFOAM

对初始蒸汽质量分数在0.5以上的干空气-蒸汽混合气泡在过冷水中的冷凝过程进行了数值研究。基于开源软件包OpenFOAM中的icoReactingMultiphaseInterFoam多相流求解器对以上问题进行模拟。采用的相界面追踪方法是流体体积方法(VOF),并结合连续表面应力模型(CSF),相变Lee模型以及k-ε模型建立三维数值模型。所建立的数值模型的计算结果能够较好的和实验结果匹配,表明了此模型能够很好的对含不凝结气体的蒸汽气泡直接接触冷凝的行为进行预测。结果表明:气泡体积稳定后,气泡的形状会出现震荡;在冷凝过程中,气泡的边界附近存在温度梯度;气泡的冷凝时长与过冷度和气泡初始直径呈非线性关系;终端等效直径与气泡初始直径呈线性关系,并且对于初始不凝气含量高的气泡,其终端等效直径随初始直径的增大而增长更快;小间距的竖直气泡对,下方的气泡中的蒸汽的凝结会被抑制。

In this paper,the condensation process of air-steam mixed bubbles in water with initial vapor mass fraction above 0.5 has been numerically studied.Based on multi-phase flow solver of open source software package OpenFOAM icoReactingMultiphaseIterFoam for simulating the problem above.The phase interface tracing method is fluid volume method(VOF),combined with continuous surface stress model(CSF),Lee model and K-εmodel to establish numerical model.The calculated results of the established numerical model match the experimental results well,which indicates that the model can predict the behavior of direct contact condensation of steam bubbles containing non-condensing gas well.The results show that:After the bubble volume stabilizes,the shape of the bubble will appear oscillation.During condensation,there is a temperature gradient near the bubble boundary.There is a linear relationship between the terminal equivalent diameter and the initial bubble diameter.For the bubble with high initial non-condensing gas content,its terminal equivalent diameter increases faster with the increase of initial diameter.In pairs of vertical bubbles with small spacing,condensation of steam in the bubbles below is inhibited.