Mathematical Modeling And Heat Transfer Performance Simulation Of Steam Generator

Nuclear power plant steam generator is an important operating equipment of double-loopnuclear power plant and it is a hub to connect the primary side and secondary side. If nuclearpower plant can be safe and efficient operation is determined by inherent characteristics andworking condition of steam generator in a great extent. So it seems important that modelingsimulation is done to analyze working performance of steam generator by usingthermal-hydraulic calculation and computer simulation methods.Taken steam generators of Daya Bay Nuclear Power Plant as the prototype, theone-dimensional homogeneous flow and two-phase flow dynamic mathematics model ofnuclear power plant steam generator is built on the research object, the primary side, thesecondary side fluid and the inner and outer wall of U-tube, based on distributed parametermethod. Runge-Kutta method is used to discretizate differential equation. Jacobi iterativemethod and Gauss elimination method are used to solve steady-state linear equations.Simulation program is compiled based on MATLAB. Steady-state and dynamic heat transferperformance simulation of steam generator are conducted. Simulation results of two modelsare compared finally.Simulation results based on homogeneous flow model show that100%,70%,50%,30%,10%operation results are got. Outlet temperature of primary side fluid does not vary withpower. Outlet temperatures of U-tube wall and secondary side fluid increase with power drops.Outlet enthalpy and vapor mass fraction of secondary side boiling-section decrease withpower drops. While operation drops from full power to70%power, temperatures of primaryside and inner wall decrease as time, temperatures of secondary side and outer wall graduallyincrease as time and outlet enthalpy and vapor mass fraction drop. When power uprating isconducting, the secondary side preheating-section becomes shorter. Outlet enthalpy and massfraction increase. Temperatures of the primary and secondary side decrease and temperatureof the tube wall is lower generally.Simulation results under full power based on two-phase flow model show that thesecondary side vapor and liquid velocity rises. Slip ratio increases from zero and falls sharplyafter arriving at maximum. At last it trends to a steady state. Cross-section void fraction shows a rise trend.100%,70%,50%,30%,10%steady-state operation results are got.Vaporand liquid velocity, maximum of slip ratio and outlet cross-section void fraction decrease aspower drops. Compared parameters of two-phase flow model with homogeneous flow model,mixing speed based on homogeneous flow model is between vapor velocity and liquidvelocity. Vapor mass fraction based on homogeneous flow model is slightly higher than resultof two-phase flow model.To sum up, operating characteristics of steam generator is analysed in this paper. Badplace of work condition and accident-prone point are obtained. It prevents steam generatortube explosion accident because of overheating and provides technical support forestablishing solution scheme, so as to improve safety and reliability of nuclear powerequipment.