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A three‐dimensional numerical analysis was carried out to study in detail the combined heat and mass transfer processes between a moist air flow and a cooled surface when film condensation occurs. A cross‐flow was considered between the air flow and the film flow. A turbulent flow was modelled using the Wilcox k−ω turbulence model. The shape of the interface between the air and the film was treated as a moving boundary, and it was calculated with the assumptions that the interface ways remain an interface, the stress at the interface is continuous and that there is no slip at the interface. Numerical results were obtained by solving simultaneous coupled equations of the air, film and solid. The results show that the condensate film flow has a significant effect on the extended surface temperature distribution and consequently on its efficiency. It is shown that the simultaneous influence of gravity and the air flow on the condensate film results in an asymmetric velocity profile in the film as well as in the asymmetric shape of the film.