A unified wall function for wall condensation modelling in containment multi-component flows

•A unified formula is given for the wall function in mixed convection flows.•A smooth transition way is proposed for wall function from natural convection to forced convection.•The resolved boundary layer method is used to validate the wall function method for wall condensation.•Different test cases are calculated to validate the capability of the wall condensation model. One of the major difficulties in modelling the steam condensation in the containment under accidental scenarios arises from the complicated flow patterns. Although empirical correlations have been established to predict the heat and the mass transfer on the wall surfaces, it is difficult to apply the relations to real containments for the different flow patterns within the multiple compartments and the difficulty in defining the non-dimensional numbers under complex geometry. The application of the resolved boundary method is also limited since it requires very fine grids inside the boundary layer. This paper proposes a unified wall function method to calculate the heat and the mass transfer on the wall surfaces under mixed convection flows. A series of benchmark tests are used to validate the proposed method and it is shown the method is applicable to a wide range of flow regimes.