NUMERICAL STUDY OF HEAT TRANSFER IN A DISTORTED ROD BUNDLE
The effect of rod distortion on the flow and heat transfer in a rod (fuel) bundle similar to those in an Advanced Gas-cooled Reactor (AGR) is investigated. Despite the use of such a specific configuration, the results are of relevance to various other engineering applications, for example heat exchangers. The domain under investigation is made of two sections: the first consists of an undamaged section at nominal pitch to diameter (p/d) ratio, which allows the flow to develop. The second section is a distorted bundle: the p/d ratio reduces gradually over the first half of the bundle, reaching a minimum at half high, then increases back to its normal value over the second half of the bundle. In this paper, the results for forced convection are presented. Changes in the rod profiles are shown to divert flow to regions of less resistance. As a consequence of flow diversion cross flow recirculation regions occur. In these regions temperature spots are observed, with peak rod temperatures occurring after the location of minimum p/d ratio. Axial temperature variation within the subchannels is also shown to be complex.