Development of a Convective Heat Transfer Measurement Technique for Flow Downstream of Support Grids in Rod Bundles

Abstract

Convective heat transfer coefficients are measured for flow downstream of support grids in a rod bundle. The rod bundle geometry consists of a 5×5 square array of parallel rods that are held on a constant pitch by a series of support grids spaced axially along the rod bundle. The rods are heated using direct resistance heating, and a bulk axial flow of air is used to cool the rods in the rod bundle. The support grid designs are modified to enhance the local heat transfer in the rod bundles. The present study examines the heat transfer enhancement downstream of standard, disc, and split-vane pair support grid designs. Results indicate that the heat transfer downstream of the support grid designs is enhanced for up to 10 hydraulic diameters downstream of the support grid. The heat transfer enhancement for the disc and split-vane pair support grid designs is greater than that of the standard support grid design. The heat transfer development downstream of the split-vane pair support grid designs indicates a decreased region of heat transfer below that of the fully-developed heat transfer for the Reynolds numbers investigated. The heat transfer results are the first presented in the open literature for flow downstream of a fully-heated span for disc and split-vane pair support grid designs.