Experimental Investigation of the Subchannel Axial Pressure Drop and Hydraulic Characteristics of a 61-Pin Wire Wrapped Rod Bundle

Abstract Wire-wrapped hexagonal fuel bundles have been extensively investigated due to their enhanced heat transfer and flow characteristics. Experimental measurements are important to study the thermal-hydraulic behavior of such assemblies and to validate and improve the predictive capabilities of specialized correlations and computational tools. Presently, very limited experimental data is available on the local subchannel pressure drop. Experimental measurements of subchannel pressure drop were conducted in a 61-pin wire-wrapped rod bundle replica, for Reynolds numbers between 190 and 22,000. Specialized instrumented rods were utilized to measure the local pressure drop and estimate the subchannels' friction factor. Three interior subchannels, one edge subchannel, and one corner subchannel were selected to study the effects of location and flow regimes on the friction factor and hydraulic behavior. The transition boundaries from laminar to transitions regimes, and from transition to turbulent regimes were estimated for the subchannels analyzed. The results were found to be in agreement with the predictions of the upgraded Cheng and Todreas detailed correlation (UCTD). The results of the experimental campaign provided a better understanding of the hydraulic behavior of the subchannels of wire-wrapped bundles, in relation to its geometrical features.