Experimental investigation of the crossflow of water in a 7-pin wire-wrapped rod bundle

Abstract

In this study, the crossflow of water in a 7-pin wire-wrapped rod bundle was investigated experimentally using particle image velocimetry and the technique of matching index of refraction. Three Reynolds numbers, 3000, 6000, and 9000, were used to examine the effect of the Reynolds number on crossflow. A large-dimension rod bundle was utilized to provide sufficient space for high-resolution measurements. The cross-sectional flow distribution in the wire-wrapped rod bundle was obtained. Both global circulation flow in the bundle outer region and local reverse flow in the bundle interior were identified. In general, crossflow distribution is complex and is characterized by vortices of various scales. Previously, a large-scale vortex has been observed near the rod, which is related to the wall-fluid interaction. However, small vortexes are likely to appear on the lead side of the wire, which is attributed to the blockage effect of the wire. The distributions of the dimensionless velocity and turbulent kinetic energy in three typical subchannels were studied. The features of streamwise flow were also examined briefly. The flow blockage and redistribution caused by the wrapped wires were observed. The experimental data can be applied to validate CFD codes, turbulence models, and subchannel crossflow models.