Numerical Investigation Of The Thermal-hydraulic Characteristics Of PWR Steam Generator Based On CFD

Steam generators(SGs)play a key role in connecting the primary and secondary circuits in the pressurized water reactors(PWR)of nuclear power plant.They comprise not only the primary side pressure boundary that prevents the release of radionuclides but also the heat transfer boundary for fluid going from the primary to the secondary side.Therefore,it is important to study the thermal-hydraulic characteristics of SGs to prevent the SG tube rupture(SGTR)accidents and to improve the safe operation of nuclear power plants.At present,most scholars used a porous medium model to study SGs,which can effectively predict the thermal-hydraulic characteristics of the SG.However it has certain limitations,and the local thermal-hydraulic phenomenon of tube bundles in the SG cannot be obtained.In this paper,CFD code is used to analyze the thermal-hydraulic characteristics of SG tube bundles.A coupled model of the primary side,heat transfer tube and secondary side of SG with the trefoil tube support plates(TSPs)is developed to calculate the thermal-hydraulic characteristics of the AP1000 SG.Using ANSYS CFX 18.0,a thermal phase change model is used to calculate the coupled heat transfer process between the primary side fluid and the secondary side fluid of tube bundles.The simulation results reasonably reveal the distribution of key parameters,such as steam quality,temperature,velocity,heat transfer coefficient,etc.The influences of different inlet subcooling on the thermal-hydraulic characteristics of the SG are also investigated.The results show that the slip-ratio first increases sharply and then decreases slowly along the flow direction of the secondary side.The simulated heat transfer coefficient agrees well with the result of the Rohsenow formula.The most severe flow-induced vibration(FIV)damages is predicted at the angles of ?=60° on the cold leg and ?=110° on the hot leg based on the cross-flow energy over the U-bend region,and the results are in good agreement with predictions using the porous media model.By comparing the model with and without TSPs,the influence of the trefoil TSPs on the thermal and hydraulic characteristics of the heat transfer tube is obtained.Due to the effects of the TSP,the fluid velocity of the secondary side changed abruptly,thus generating local vortexes.The circumferential of the outer wall temperature appears a periodic characteristic in the TSPs regions,which increase the possibility of concentrated aggressive solutes and tube rupture.Under the condition of natural circulation in reactor systems,reflux may occur at U-tubes of SG.Taken the AP1000 SG as the prototype,the thermal-hydraulic characteristics of the SG reflux are investigated.In this paper,the SG U-tubes are divided into six groups according to their lengths,and the flow and heat transfer characteristics of single-phase fluid in the U-tubes are analyzed with CFD methodology.The trends of total pressure drop against mass flow rate are derived based on the simulation results.The influence of the U-tube length and the temperature difference between the primary side fluid and the secondary side wall on the reflux are discussed.It is shown that when the temperature difference is constant,the reflux occurs more often in the longer U-tubes.When the U-tubes length is constant,the smaller the temperature difference is,the more often reflux occurs.