Implementation of a CFD methodology for computing subchannel friction factors and split parameters in wire-wrapped rod bundles

Abstract

A Computational Fluid Dynamics (CFD) model is presented to simulate an isothermal flow within a 61-pin wire-wrapped fuel assembly, typically employed in Liquid Metal Nuclear Reactors. A methodology is proposed to compute subchannels friction factors and split parameters, which are relevant variables for reactor licensing calculations and safety evaluations. Five subchannels are analyzed: three interiors, one on the edge and one at the corner. The model is validated with pressure drop experimental data of the different subchannels measured at the Texas A&M Thermal-Hydraulics Research Lab. The CFD pressure drop results are found in correct agreement with the experimental data. The subchannels parameters are compared with the predictions of the UCTD and PCTD correlations to evaluate their performance. Results indicate a reasonable agreement at turbulent regime, while the highest differences between the CFD model and the correlations are found at laminar regime. Therefore, the use of numerical simulations can be a suitable strategy for improving the correlations at low Reynolds numbers.