A preliminary assessment on a two-phase steam condensation model in nuclear containment applications

Steam condensation in the presence of air is a vital heat transfer process in postulated loss of coolant accidents. To numerically evaluate local and global thermal hydraulic properties, several single-phase models have been developed in previous studies. However, potential mutual interactions between the liquid and gas phase (e.g. evaporation, radioactive material retention, etc.) impose requirements on two-phase models. Accordingly, the present work performed CFD evaluations on a two-phase boundary layer model (TPBL) which concerned the gas phase, liquid phase and their mutual interactions. Assessments were performed by comparing calculated results with the COPAIN and TOSQAN experimental data. The COPAIN cases show that predicted local and average heat fluxes are generally within 25% and 15% deviation, respectively. Detailed properties were obtained on the formation, distribution, and thermal resistance of liquid film as well as the model computational costs. In the TOSQAN cases, two steady states, including steam-air mixtures and steam-air-helium mixtures were considered. Via these cases, the applicability of the TPBL model in predicting local field profiles like velocity, temperature and concentration distribution was discussed. Results demonstrate that the calculated results overall agree well with the experimental ones. In general, the TPBL model is feasible in postulated accident analysis.