A Generalized Prediction Method for Single-Phase Pressure Drop in a String of Alinged CANDU-type Bundles

Abstract

A generalized prediction method has been developed to calculate various pressure-drop components over a string of aligned CANDU-type bundles in single-phase flow. The friction factor is evaluated using the Colebrook equation based on the surface roughness. It is modified with two correction factors to account for the geometry effect (i.e., from a tube to a bundle) and the bundle-eccentricity effect. The pressure loss over the bundle junction is assumed to be caused by (a) the flow impact loss on the exposed regions of the endplate, and (b) the separation loss between two planes of rods. The flow-impact loss is determined using a correlation based on the blockage-area ratio, whereas the separation loss is calculated using data obtained from a bundle separation test. The pressure drop at either the spacer plane or the bearing-pad plane is calculated based on the blockage-area ratio. Modification shave been introduced to account for (a) the rounding of the leading and trailing edges of a spacer, and (b) the 15 degrees offset from the flow direction. The prediction method has been validated using experimental data obtained with several bundle strings. Good agreement with experimental data was observed for both the frictional pressure drop and the local pressure drops over the junction and the spacer planes.