Computational fluid dynamic simulation of swirl flow in hexagonal rod bundle geometry by split mixing vane grid spacers

Abstract

Heat transfer and pressure drop are numerically investigated for turbulent flows through a hexagonal fuel rod bundle. For the purpose of numerical analysis, the geometric and boundary conditions were taken from the VVER-1000. Since VVER-1000 does not have mixing vane on the grid spacer of the fuel assembly, split mixing vane is designed to boost turbulent flow and heat transfer in the rod bundle subchannels. The computational domain including two grid spacers extend from 100 ? Dh upstream of the first grid spacer to 250 ? Dh downstream of the second grid spacer. The steady-state form of the RANS, mass, energy and turbulence equations was discretized and solved using ANSYS-CFX. The standard k-? model is employed to simulate turbulence. The results show a considerable increase in the average heat transfer to ~10 ? Dh downstream of the grid spacer using the mixing vane on the grid spacer of VVER type reactor. As expected, the pressure loss through the grid spacer also increased slightly with the mixing vanes.