ASSESSMENT OF THE RANS TURBULENCE MODELS FOR A TURBULENT FLOW AND HEAT TRANSFER IN A ROD BUNDLE

摘要

A computational fluid dynamics (CFD) analysis has been performed to assess the Reynolds Average Navier-Stokes (RANS) turbulence models to predict a turbulent flow and heat transfer in a triangular rod bundle with pitch-to-diameter ratios (P/Ds) of 1.06 and 1.12. The CFD predictions using various turbulence models were compared with experimental results. Anisotropic turbulence models such as the nonlinear k — ε and the second-order closure models predicted the turbulence-driven secondary flow in the triangular channel and the distributions of the time mean velocity and temperature showing significantly improved agreement with the measurements from the linear standard k — ε model. The anisotropic turbulence models predicted the turbulence structure for a rod bundle with a large P/D fairly well but could not predict the very high turbulence intensity of the azimuthal velocity observed in the narrow flow region (gap) for a rod bundle with a small P/D.