Thermal Fatigue Analysis And Design Of A Fixed Tubesheet Heat Exchanger With A Nuclear Safety Level

A large number of fixed tubesheet heat exchangers are used in nuclear power plants. Many of the heat exchangers in the safety system play a function of heat removal, to ensure the normal and safe operation of nuclear power plants. The design of nuclear safety level heat exchanger is one of the important factors to ensure the safe operation of power plant. According to the requirements of RCC-M and ASME III, the influence of transient fluctuation of the system on the fatigue damage of the heat exchanger is required when designing a nuclear safety level heat exchanger. The thermal stress in the fatigue analysis is caused by the change of the metal temperature of the equipment, but not the change of the temperature of the fluid. At the same time, the designer of the system provide the designer of the equipment at the entrance of the flow, temperature, pressure transient, the export of the transient needs equipment design considerations.The starting point of thermal fatigue analysis of the heat exchanger is the fluid transient change curve of the tube inlet and the shell side inlet. The key areas of the heat exchanger are the inlet water chamber, the outlet water chamber and the tubesheet. In the previous engineering calculation, mechanics calculation model input thermal boundary conditions for fluid-solid exchange heat coefficient, that changing heat transfer coefficient is infinite, so that the fluid transient changes can be instantaneous transfer to solid, so the calculation results are very conservative. Based on this kind of conservative calculation, the design life of the heat exchanger is limited, and the economy of the nuclear power plant is reduced.In the context of nuclear power going out, nuclear power plant design under the premise of ensuring nuclear safety, improve the economic nature of the construction of nuclear power plants. In this paper, a complete set of calculation procedure and method is established for determining the thermal boundary conditions of the heat exchanger by using the combination of lumped parameters method and computational fluid dynamics. Under the method that the tube side inlet and the shell side inlet fluid parameters are known, the reasonable outlet flow and the heat transfer coefficient of the fluid in the area of fatigue analysis are obtained.The fixed tubesheet heat exchanger tube side and shell side outlet/inlet fluid transient and local fluid-solid heat transfer coefficient as the third kind of complete thermal boundary condition input mechanical calculation model, the analysis area metal temperature stress is obtained, fatigue analysis and evaluation of the concerned area according to the RCC-M standard.