Numerical Simulation of Wall Condensation Phenomenon of Steam in Containment Based on Code HYDRAGON

In order to simulate the wall condensation phenomenon of steam in containment during a severe accident in a nuclear power plant, a wall condensation model is added in code HYDRAGON, a computational fluid dynamics（CFD） code specialized for the containment hydrogen analysis. The model, which is established on the analogy theory between heat and mass transference, provides boundary condition, mass source and heat source for Navier-Stokes equations. In order to validate the model and the code, a TOSQAN experiment is selected from published literatures as a test case to be compared with the simulation results. The study manifests that the computation results agree well with the experiment data. An analysis of the results also shows that the wall condensation phenomenon works in two aspects. On one hand, wall condensation decreases the amount of steam and mitigates the increase of pressure in the containment. Meanwhile, the percentage of non-condensable gases（e.g. hydrogen） increases. On the other hand, the near-wall convective heat transfer caused by condensation intensifies the flow of gas in the system. It is unfavorable for the formation of a stable stratification zone of hydrogen at the top of containment and can reduce the hazard of hydrogen explosion.