Thermal–hydraulic performance of a 5 × 5 rod bundle with spacer grid in a nuclear reactor

Highlights: • A numerical method is proposed for the complex structure of the fuel rod bundle. • Complex flow and heat transfer in the rod bundle is obtained and analyzed. • The numerical result agrees well with the experimental result. • Detailed thermal–hydraulic performance in the complex rod bundle is presented. - Abstract: The turbulent flow behavior and heat transfer performance of the rod bundle with spacer grid have significant effect on the thermal–hydraulic characteristics in Pressurized Water Reactor (PWR). The complex structure of the spacer grid includes dimple, mixing vane and spring. In this paper, different turbulence models are coupled with the Computational Fluid Dynamics (CFD) analysis for the complex flow in rod bundle, and the numerical results are compared with the experimental results with temperature distribution at outlet. This paper focuses on thermal–hydraulic behavior downstream of the spacer grid caused by mixing vane, dimple and spring. Two types of rod bundles are investigated, including with spacer grid and without spacer grid. According to the numerical study, the strong secondary flow induced by the spacer grid gradually decay along the rod bundle after the mixing vane, and this secondary flow has significant effect on the heat transfer. In addition, a normalized Nusselt number (Nu) and swirl factor are defined to investigate the thermal–hydraulic performance of the rod bundle.