Analysis of Fluid-Solid Interaction Contributing to Thermal Fatigue in T-Junction Pipes of Nuclear Power Reactors using STAR-CCM+

Abstract

The focus of this project is on the investigation of phenomena causing degradation of specific zones of piping considering high temperature single-phase mixing in the location of T-Junction in Nuclear power plants. At these locations, thermal stratification and/or turbulent mixing are capable of generating damage-inducing thermal fluctuations of appropriate frequency and amplitude. Fluctuating stresses imposed on this section of the piping system are possible grounds of thermal fatigue failures in piping systems of nuclear power plants resulting into leakages of coolant. These stresses are produced mainly because of the temperature fluctuations that exist in regions where cold and hot streams are vigorously mixed together. A classic scenario for such mixing appears in turbulent flow via a T-junction. In this study, the purpose will be to perform a 3-D Simulation of fluid-Solid Interaction at a mixing Joint. Two different simulations of thermal mixing in T-junction of a nuclear power plant will be considered and perform thermal analyses of parameters leading to structure degradation. Pipe dimensions and flow parameters such as wall thickness and high operating temperatures difference are modeled and corresponding fluid-solid interaction‘s effect on wall thickness is investigated by using STAR-CCM+ Code for the simulations, where which fluid-flow calculations will be carried out. Thereafter, the flows inlet temperature will be interchange and another simulation conducted with same parameters so as to determine the effect in a different possible scenario. The flow characteristics and the temperatures in the pipe wall downstream are obtained using this Computational Fluid Dynamics. Simulations result and validation outputs with T-Junction experiment carried out at the FSI Test Facility, University of Stuttgart and contributions of the various investigated parameters contributing to thermal fatigue were presented.