Development of friction factor correlations for hexagonal and square bundles with rough rods based on CFD

Abstract

Changes in fuel assembly roughness caused by crud deposits can influence the flow resistance characteristics of the fuel assembly. The existing correlations cannot accurately predict the friction factor of the rod bundle with different wall roughness. The friction pressure drop factor of the rod bundle was calculated using the two-equation k-ω shear stress transport (SST) turbulence model to investigate the impact of surface roughness on the friction pressure drop factor of the rod bundle. Two new friction factor correlations are proposed based on the simulation results. The new correlations can accurately predict the pressure drop of the rod bundle in the laminar flow region, the transition region, and the turbulent flow regime. The application ranges of the new correlations are 1.1 < P/D < 1.5, 100 < Re < 700000, and the absolute roughness within 100 μm. The new correlations will be helpful in the design and safety analysis of light water reactors.