Vibration Analysis of a Multi-span Tube in a Bundle

Nuclear and process industry has seen tube bundle failures more frequently in recent years. There is some concern that the practice of structural configuration has not advanced as rapidly as thermal design of heat exchangers. Catastrophic vibration of tube in a bundle can be avoided if the tube natural frequency is kept well above the estimated existing turbulent buffeting frequencies. Flow distribution and partial admission in to the tube bundle due to upstream piping further complicates the system. In this paper, tube in a bundle has been modeled as a beam on multiple supports. Effects of damping and motion of boundaries have also been considered. Governing equations have been solved analytically for natural as well as forced vibrations. The model has been extended for a bundle of tubes by developing and implementing a computer code. Subsequent experimental verification of results on a research heat exchanger bundle has been carried. The proposed model is expected to prove a useful guide in predicting the vibration behavior of tube bundles. (authors)