PIV measurement of the vertical cross-flow structure over tube bundles

Shell and tube heat exchangers are among the most commonly used types of heat exchangers. Shell-side cross-flow in tube bundles has received considerable attention and has been investigated extensively. However, the microscopic flow structure including velocity distribution, wake, and turbulent structure in the tube bundles needs to be determined for more effective designs. Therefore, in this study, in order to clarify the detailed structure of cross-flow in tube bundles with particle image velocimetry (PIV), experiments were conducted using two types of model; in-line and staggered bundles with a pitch-to-diameter ratio of 1.5, containing 20 rows of five 15 mm O.D. tubes in each row. The velocity data in the whole flow field were measured successfully by adjusting the refractive index of the working fluid to that of the tube material. The flow features were characterized in different tube bundles with regards to the velocity vector field, vortex structure, and turbulent intensity.