Isothermal study of the flow at the junction between an auxiliary line and primary circuit of pressurised water reactors

摘要

This paper deals with an experimental and numerical study of an isothermal flow at the junction of a high Reynolds number piping system and both very small and zero flow-rate pipe. The motivation is to understand and model the hydraulic behaviour of various auxiliary lines connected to the primary circuit of Pressurised Water Reactors. Experimental data have been obtained on a hydraulic mock-up using flow visualisation method and particle image velocimetry (PIV). They shown an helicoidal flow extending along the auxiliary pipe. Numerical calculations performed with the 3D ESTET code are presented and contrast the performance between ak-epsilon eddy viscosity model and a second moment closure turbulence model. Coarse (100 000), medium (400 000) and fine (1 500 000) meshes were used to test the influence from mesh. The numerical results obtained with the second moment closure turbulence model and the finest mesh confirm the swirl flow structure into the dead leg observed on the mock-up. On the other hand thek-epsilon eddy viscosity model is not able to predict the vortex penetration along the auxiliary pipe. These results illustrate the necessity to use second moment closure turbulence model to simulate flows in piping system dead legs.