Abstract: The passive containment cooling system (PCCS) is widely used in the next generation of nuclear reactor systems to maintain the integrity of containment for longer time after utmost accidents such as the loss of coolant and main steam line break. For double concrete containment, the condenser is one of the most essential equipment in the PCCS and its heat transfer capability determines its performance. In the steam condensation process, the presence of large amounts of non-condensable gases will lead to serious deterioration of heat transfer, so further study on steam condensation in the presence of air must be conducted. In this study, condensation processes of steam in the presence of air are modeled by applying a user defined function added to the commercial computational fluid dynamics package. Calculated profiles of temperature, air concentration, velocity components and condensation heat transfer coefficient are compared to experimental results. The simulation results indicate a good agreement between the experimental results and model predictions. It also shows that both the latent and the sensible heat transfer coefficient decrease with the increase of air mass fraction, and the latent heat transfer is a dominant factor in the total condensation heat transfer at air mass fractions less than 50%. Local latent heat coefficient presents an upward tendency along the axial direction of heat transfer tube from the bottom to the top, while the sensible heat transfer coefficient takes an opposite trend.

Key words: air, condensation, heat transfer, latent heat transfer coefficient, numerical simulation

摘要： 根据已有的传热传质关系式，通过CFD软件在控制方程中加载控制方程源项，建立了含空气蒸汽冷凝的数值计算模型，运用此模型对两种实验的共10组工况进行了数值计算。结果表明，计算模型对两组实验在压力、温度、空气含量以及冷凝传热系数的预测方面均有较高的准确度；潜热传热系数及显热传热系数都随着空气含量的升高而减小；在空气质量分数低于50%的工况下，潜热换热是冷凝传热的主导因素；局部潜热传热系数沿传热管高度方向从下至上呈递减趋势，而局部显热传热系数则呈现相反变化。

关键词: 空气, 凝结, 传热, 潜热传热系数, 数值模拟