Methods of Analysis of Tube Array Fluid Elastic Instability Data

Abstract

Fluid-elastic instability (FEI) is the cause of mechanical failures and expensive damage in tube bundle heat exchangers. The purpose of this experimental study is to develop a methodology to analyze the vibrations due to fluid-elastic instability in a tube array. The motions of a square array of 15 stainless steel vibrating tubes (␀ 25.4mm) in water cross-flow, suspended using stainless steel piano wire have been recorded with a CCD camera. The captured images are analyzed using two different methods. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Eventually, critical velocities for various tube array configurations and flow conditions can be measured and compared with existing criteria for heat exchanger design and operation.