Turbulent flow through spacer grids in rod bundles

The effects of the spacer grids with mixing vanes in rod bundles on the turbulent structure were investigated experimentally. The detailed hydraulic characteristics in subchannels of a 5 X 5 rod bundle with mixing spacer grids were measured upstream and downstream of the spacer grid by using a one component LDV(Laser Doppler Velocimetry). Axial velocity and turbulent intensity, skewness factor and flatness factor were measured The turbulence decay behind spacer grids was obtained from measured data. The trend of turbulence decay behaves in a similar way as turbulent flow through mesh grids or screens. Pressure drop measurements were also performed to evaluate the loss coefficient for the spacer grid and the friction factor for a rod bundle.