Heat transfer in rod bundle subchannels.

Abstract

Presented in this study is an experimental investigation of heat transfer in a model of the 37-rod CANDU reactor bundle. Localized heat was provided by a narrow heated strip mounted on the central rod, which could be traversed within the duct and rotated about its axis. The relative variation of the "apparent" local heat transfer coefficient around the central rod was determined for various rod-wall proximities including two limiting cases of rod-wall contact and rod-rod-wall contact. The flow temperature measurements were concentrated on the rod-wall gap variation. The statistics of the temperature fluctuations showed a deviation from Gaussianity, that was more pronounced as the gap diminished. Asymmetry of the mean temperature and the temperature fluctuation contours is observed with the heater near the gap as well as facing the sub-channel centre. (Abstract shortened by UMI.)