Numerical Simulation Research On Steam Transport And Condensation Characteristics In Containment

In nuclear power plant,under the condition of design basis accidents like LOCA(Loss of Coolant Accident)and MSLB(Main Steam Line Break accident),large amounts of steam with high pressure and temperature will release into containment and increase its inner pressure and temperature which may damage its integrated.In order to protect the last security barrier which inclusive radioactive products from destroyed,these released steam with high temperature and pressure should be condensed timely and effectively.The passive containment cooling system(PCCS)in advanced pressurized water reactor nuclear power technology is the ultimate heat sink that can effectively cool the steam that released in containment and ensure the containment will not fail of overpressure.Therefore,the in-depth study of PCCS has important significance.Among them,research on the mix flow of air and steam in containment and condensation of steam with non-condensable gases presence on steel containment is one of the key issues in the PCCS system.In this paper,computational fluid dynamics analysis was used.Containment three-dimensional geometric simulation model was established by using Pro/E software,the internal structure of the containment was appropriate simplified.Steady state natural circulation of air convection heat transfer within the containment was calculated.The magnitude relationship between Convective heat transfer and Radiation heat transfer under this condition was compared.The results show that radiation heat transfer and convection heat transfer in the same order of magnitudes,and the value is greater than the convective heat transfer.Three-dimensional numerical simulation of steam condensation with non-condensable gas presence in containment was achieved by loading UDF calculated model in FLUENT.Steam flow distribution in containment and condensation heat transfer characteristics on containment wall of constant steam mass flow was simulated.The results show that under this condition,the upper space of containment has higher steam concentration,and steam distribution appears obvious stratification.During total steam condensation process,condensation heat transfer is 2 to 3 times higher than convection heat transfer.Both condensation heat transfer coefficient and the convective heat transfer coefficient increase with the increase of steam mass fraction and decreasing from top to bottom along containment wall.Two correlations were used to calculate condensation heat transfer coefficient,the result show that Uchida correlation is more conservative.Through the comparison and analysis of steam distribution and condensation features under these three different steam inlet conditions found that inlet velocity has a significant influence on steam flow distribution and condensation properties in containment.