CFD verification for rod bundle under single phase flow condition

Abstract

Computational fluid dynamics (CFD) is known as a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems related to flow fields in many industries including the phenomena occurring in the reactor coolant system. The purpose of this study is to conduct the CFD simulation for the test rod bundle, set up the CFD simulation procedure for the specific analysis of the complex flow field within the fuel assembly and review its application for the core thermal-hydraulic design and new fuel assembly development. The CFD verification for the rod bundle test was performed using FLUENT 14.5 in single-phase flow condition. First, the CFD simulation for the 4x4 rod bundle test with a spacer grid in the middle location showed a good agreement within 5% except for the corner subchannel compared with the experimental data. At this time, the mesh for the CFD simulation was generated by T-grid (fluent meshing) and $y^+$ was within 5. Mesh independent and turbulence model tests were conducted at each run case and the solver used SIMPLE algorithm. Also, the standard k-omega turbulence model showed the best agreement to the experiment value. Next, the CFD simulation for 5x5 rod bundle of the thermal mixing flow test was carried out based on the this procedure. The configuration of this test consists of seven mixing vane spacer grids. The measurement temperature profile for each subchannel at the end of heated length was a similar tendency to that of CFD simulation and the maximum temperature deviation overestimated about 5 K (Measurement average temperature : 495 K). Therefore, CFD simulation showed a good agreement compared with the experiment data. At this time, k-epsilon turbulence model was used because the deviations with the experimental data were smaller than the result by k-omega model. The results by CFD simulation for 5x5 rod bundle of thermal mixing flow test were compared with those by the subchannel analysis code at the end of...