This work studies the hydrodynamics of the seven pin wire-wrapped rod bundle in the sodium cartridge loop for the Versatile Test Reactor (VTR) through scaled water experiments and computational fluid dynamics (CFD) simulations. The scaling analysis is first performed to demonstrate the hydrodynamic similarity between water and sodium flows at the same Reynolds number Re. A separate-effects test facility is designed and constructed based on the scaling analysis. Detailed experimental data on the pressure drop covering a wide range of Re values (1165 to 27 689) are obtained, which are used to evaluate existing correlations for friction factor and to benchmark CFD simulations. The experimentally determined friction factors f(Exp) agree well with the Upgraded Cheng and Todreas Detailed Correlation and Pacio-Chen-Todreas Detailed Model within +/- 7 but are significantly underpredicted by Rehme's correlation by 25. Various CFD near-wall treatment methods are tested using ANSYS Fluent and evaluated by experimental data. It is found that when the recommended wall y(+) values are met, most of the near-wall treatment methods can give accurate friction factor predictions. The resolved near-wall method (y(+)similar to 1) with the Shear Stress Transport k - omega turbulence model and the scalable wall functions (y(+) > 12) with the realizable k - epsilon turbulence model can predict f(Exp) within +/- 5 The standard wall functions (y(+) > 30) and nonequilibrium wall functions (y(+) > 30) with the realizable k - s model can predict f(Exp) within +/- 10.
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