Thermal Fluid Coupling Analysis Of Steam Generator Heat Transfer Tube With Support Plate

In PWR nuclear power plant,steam generator is not only a pressure boundary of primary loop,but also an visual equipment connecting nuclear island with conventional island.Through fluid-heat-solid coupling with heat transfer tube,the heat transfer from primary side to secondary side is completed.At the same time,the steam generator blocked the direct convection on the primary side and the secondary side,which constituted the second barrier in the reactor shielding system to prevent radioactive materials from leaking to the environment.However,most of the domestic and international research on steam generator is still based on one-dimensional numerical model,which can not directly and accurately reflect the thermal hydraulic characteristics of steam generator in three dimensions.In this paper,the local thermal hydraulic analysis of the direct pipe section of the steam generator is carried out based on the CFD method,and the results are compared with the results of the numerical model with the support plate.Based on the steam generator of Daya Bay 900MW nuclear power plant and guided by the similarity principle,a mathematical physical model is established,which is in line with the actual size of the primary loop,the secondary loop,the heat transfer tube and the supporting plate.Through the computational fluid dynamics simulation software CFX,the numerical simulation of the three-dimensional flow and coupled heat transfer process is realized.The secondary side is used in two-fluid and Euler mathematical model,considering the energy and mass between gas and liquid phase conversion,to avoid the porous medium model with single heat source as thermal boundary conditions,while ignoring the two side vapor-liquid conversion and heat transfer tube heat transfer effect.Through this numerical simulation,the distribution rule of key parameters such as steam vapor rate,heat transfer coefficient,pressure and temperature of Daya Bay nuclear power plant under steady-state operation conditions is obtained.The calculation results show that;Due to the reduction of the flow section at the support plate,the flow velocity of the secondary side fluid in the gap at the support plate rises sharply,and then is rapidly reduced to form a reflux.The possibility of impurity deposition is greatly increased because of the reflux and the barrier of the supporting plate.The pressure of the fluid decreases along the axial direction of the heat transfer tube.The variation of pressure difference occurs when the support plate is flowing through the support plate,and the magnitude of the mutation amplitude varies with the change of the resistance loss of the secondary lateral fluid.The temperature of the heat transfer tube is periodically changed in the vicinity of the supporting plate,which increases the fatigue damage and the probability of stress corrosion in the heat transfer tube.By using the thermal phase transition boiling model,the position of the starting point of the secondary side boiling point and the vapor content of the outlet can be predicted accurately and effectively.