An Experimental Study on the Identification of Flow Patterns Responsible for Crossflow in a Vertical Tube Bundle Geometry

Abstract

The aim of the present study is to enhance the current understanding of crossflow in a vertical tube bundle geometry in an experimental way. LDA measurements were carried out in a 4 x 4 tube bundle having diameter to pitch ratio of 0.7 for Reynolds numbers ranging approximately from 600 to 11,000. Water was used as a working fluid at isothermal, single-phase flow and ambient operating conditions. The experimental results showed the existence of large-scale coherent structures for laminar, transitional and turbulent flows. The secondary flow patterns were resolved as well. A comparison of the root mean square of cross velocity fluctuations in the gap region, being a measure of cross-flow, with the magnitude of the secondary flows reveals a dominant contribution of the former over the latter. Furthermore, the successful use of FEP in the above-mentioned experiments as solid, refractive index matching material in water has been demonstrated.