Numerical investigation on the effects of vortex generators on sub-channel flow in a rod bundle

Spacer grids of fuel assemblies are equipped with vanes, which promote mixing and turbulence within and across the sub-channels and thereby enhance the heat transfer. In this study, we investigated the impact of vortex generating vanes on the downstream flow evolution and heat transfer from the fuel rods by numerical analyses. Simulations were performed with ANSYS CFX. We investigated the turbulence change along the channel in the presence of the vanes depending on vorticity. The use of vanes results in a vortex, in which the vorticity enhances with increasing vane angle. These change induce turbulence kinetic energy variations. Physical conditions for optimum heat transfer along the sub-channel were determined in terms of Nusselt number. The Nusselt numbers of the present simulation were compared with experimental results from literature and a slight over prediction of the simulation compare to the experiment was found.