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.