An Experimental Study on Flow-Induced Vibration of a Single and Adjacent Tubes Within a Model Helical Coil Heat Exchanger

Abstract

The helical coil heat exchanger (HCHX) is a geometrically complex tube and shell heat exchanger design that is preferred over straight tube bundles due to its increase in heat transfer efficiency, compact design, and thermal stress flexibility. Previous studies have shown prominent flow phenomena within the shell-side of the heat exchanger such as vortex shedding. A helical coil heat exchanger model was designed and constructed to study the vibration response of a single and two adjacent tubes within the center of the bundle. Results from tests conducted at Re∞ = 7,500 showed that the addition of an adjacent vibrating tube either upstream or downstream slightly increased the frequency of the motion but stabilized the vibration response. Results also showed that increasing Reynolds numbers 3,800 to 8,300 maintained frequencies of vibration from 9.17 Hz to 10.84 Hz in the x-direction and 19.45 Hz to 21.96 Hz in the y-direction. Comparisons to correlations showed a fair agreement with Weaver’s Strouhal Number equations. Safety standard equations to avoid fluid elastic instability show that the flow was within the unsteady region at even the lowest Reynolds numbers suggesting they do not accurately predict the flow development within this heat exchanger design.