Numerical Simulation Of Steam Contact Condensation In Injection Water Tank

Direct contact condensation(DCC)is widely used in nuclear power,chemical industry and other fields,such as steam jet driven ejector,contact feed water heater and nuclear reactor safety system.DCC plays an important role in thermal and hydraulic safety of nuclear power plant and nuclear power system because of its strong phase change heat transfer capability.For nuclear power or nuclear power system,in case of overpressure of primary system or overpressure of containment under LOCA accident,it is necessary to inject steam into the condensate tank to relieve the pressure.At present,the mechanism of direct contact condensation between steam and supercooled water is still unclear,so further research is needed.Based on the theoretical analysis and CFD numerical simulation,the phenomenon and heat transfer characteristics of steam jet condensation in supercooled water are analyzed in this paper.On the basis of numerical simulation,combined with the characteristics of DCC jet condensation,the transient process of large flow steam jet condensation in engineering is calculated and analyzed,and the nozzle design of large flow jet condensation is proposed.In the research of numerical simulation,the combination of VOF model and Lee model were used to analyze the steam condensation in the injection water tank in detail.At the same time,According to the characteristics of injection condensation,the condensation mass transfer coefficient of the phase-change condensation model(Lee model)was modified.Compared with the experimental results of Kim et al.,the calculation results of two-phase flow field are very similar to them.The numerical results show that There is a wave shape at the interface of velocity field of steam plume,which enhances the momentum and energy transfer between steam and water,and the flow fluctuation is extremely intense.In the affected area of injection condensation,Steam can maintain the basic characteristics of steam flow in a small range along the axial direction.Then most of the steam is quickly condensed until it is completely condensed.The numerical also results show that the condensation capacity of the steam decreases gradually increasing of the initial water temperature.At the same time,due to the existence of compression wave and expansion wave,the temperature of steam plume along the axial direction fluctuates.Combined with the numerical analysis of steam jet condensation,the transient analysis program of the condensation of injection condensation in the injetction water tank was developed.Through the analysis of the calculation program,the transient change of the parameters in the process of steam injetction and the distribution of the parameters in the equilibrium state are obtained,including the height of water level in the water tank after reaching the equilibrium state,the peak value of the mixing speed at the outlet of the injection hole,and the back punch force of the single injection hole.At the same time,the influence of non-condensable gas on the main thermal parameters of the steam emission under the accident condition is analyzed.It is found that the non-condensable gas makes the pressure value of the injection water tank suddenly increase,which needs to be considered particularly when designing of the injection water tank.On this basis,The primary design of the steam nozzle in the injection tank is carried out,and the main parameters such as the layout,size and number of injection holes are determined.