CFD Analysis of Effects of Grid Spacer Vane on Thermal-Hydraulic Performance of Fluid in a 5×5 Fuel Channel

A grid spacer with a vane is an influential segment in reactor fuel channels. A vane produces significant effects on flow mixing and augmentation of heat transfer in subchannnels. The purpose of this work was to do a computational fluid dynamics (CFD) analysis on the effects of a grid spacer vane on the thermal-hydraulic performance of fluid in a 5×5 fuel channel. A square array of a 5×5 fuel channel was used for this analysis with a pitch–to–rod diameter ratio of 1.33 and a blockage ratio of the grid spacer of 0.16. The relative study was made for the thermal-hydraulic performance among a grid spacer with a vane, a grid spacer (without a vane), and without a grid spacer (bare bundle). Analyses were made for fluid pressure of 15.5 MPa, inlet temperature of 583 K, and velocity of 4.74 m/s. The SST k-ω and RNG k-ε turbulence models were used to analyze flow phenomena and thermal performance. CFD results were validated with experiment data and were also compared with correlations proposed by researchers. The results were analyzed by different methods such as data curves, streamlines, and vector and contour plots. The results show that the strong characteristics of swirl flow in subchannels cause a greater mixing rate of turbulent flow, which hence improves heat transfer performance. The swirl ratio was observed maximum close downstream to a grid spacer with a vane. Grid spacer effects on heat transfer were noticed from z/D_h = 0 to 20 in downstream.