CFD Simulation of Single Phase Mixing in a 4x4 Rod Bundle with Different Spacers

Abstract

Enhancing heat transfer between fuel rods and coolant is one of the main goals of nuclear engineering. Spacer grids equipped with mixing vanes are placed inside nuclear fuel assemblies to enhance the lateral velocities of the flow inside the sub-channels and, also, increase the lateral mixing between different sub-channels and, consequently, the heat transfer. For the design and analysis of these spacer grids, Computational Fluid Dynamics (CFD) tools, able to compute flow structures taking into account effects such as wall friction, turbulent mixing or heat transfer, are commonly used. In this project, CFD methodologies have been developed to simulate flow field inside bare rod bundle and bundles equipped with 4 types of spacers, testing different mesh strategies and turbulence models. Behaviour of different methodologies are studied and results are compared against experimental data, and promising options are identified.