Development of a subgrid-scale liquid film condensation model for use in Euler-Euler computational multiphase flow simulations

Accurate numerical modelling of liquid film condensation is essential due to its significant influence in numerous industrial applications. The very small scale of this heat and mass transfer phenomenon motivates the development of a subgrid-scale film condensation model in this study. The developed model, for use in the computational multi-fluid dynamics Euler-Euler approach, provides physical closure for interfacial transfers when the film thickness is smaller than the near-wall mesh resolution. For pure vapour conditions, the rate of condensation is determined from the local liquid film thickness by considering pure conduction across a laminar film. The model aims to be applicable to internal convective condensation with significant shear stress at the gas-liquid interface. Moreover, the model is intended to cover all range of non-condensable gas concentration by considering both the thermal resistance of the liquid film and thermal resistance due to non-condensable gases and iteratively predicting the saturation temperature at the gas-liquid interface. A validation of the proposed model has been carried out through comparisons with an analytical model and experimental data from literature. The model has been evaluated under a wide range of operating conditions, including both pure vapour conditions and vapour mixtures with non-condensable gases. The developed model offers a satisfactory prediction of the energy transfer and condensate dynamics for laminar liquid film condensation in vertical tubes.