NUMERICAL ANALYSIS FOR EFFECTS OF GRID SPACER VANE ON FLOW-THERMAL CHARACTERISTICS OF TWO PHASE FLOW IN A 5 × 5 ROD BUNDLE

Abstract

The inclusion of a grid spacer with vane is a crucial component in reactor fuel channels. This component is employed to ensure the proper spacing and firmness of the rods during the flow operation. The presence of vane significantly influences the flow mixing and heat transfer enhancement within subchannels. The objective of this study is to conduct a numerical analysis to investigate the effects of grid spacer vane on flow-thermal characteristics of two phase flow. This investigation used a 5 &times; 5 rod bundle square array. Pitch to rod diameter ratio was 1.33, and grid spacer blockage ratio was 0.16. Eulerian model was used for two phase fluid formulation. Transient simulations were performed for the flow considerations of flow considerations of velocity 4.74 m/s, liquid temperature 583 K, volume fraction 0.35, heat flux 1500 kW/m², and pressure 15.5 MPa. The shear stress transport (SST) <i>k-&omega;</i> turbulence mixture model was used to analyze flow phenomena and thermal performance. Computational fluid dynamics (CFD) results have been validated through the comparison with experiment data. Results show that the accumulation of water vapor is greater in the central zone of subchannels compared to the surfaces of the rods. It is also observed that the vanes lead to an increase in the turbulent mixing rate within the subchannels and a notable reduction in the temperature of the liquid is observed within the grid spacer zone.