Laminar, Transition, and Turbulent Parallel Flow Pressure Drop Across Wire-Wrap-Spaced Rod Bundles

Laminar, transition, and turbulent parallel flow pressure drop across wire-wrapped hexagonal rod bundles positioned inside a duct were determined in tests using water, sodium, and air. A smooth transition region from turbulent to laminar flow that occurred over the Reynolds number range from 5000 to 400 characterized the resulting friction factor behavior. The continuous transition region could be explained in terms of the fraction of the flow area in turbulent flow. Laminar friction factors calculated from individual subchannel measurements could be correlated by the same expression found for rod-bundle-averaged conditions. In the laminar range, the friction factor was correlated by the expression f = 110/Re, in the turbulent range by f = 0.55/Re^0,25, and in the transition range by where is the intermittency factor. A general laminar flow friction factor correlation was developed: This correlation agrees satisfactorily with limited laminar flow data from rod bundles having different wire-wrap lead pitch-to-diameter ratios.