An important problem that may arise in the operation of tube and shell heat exchangers is tube vibrations, especially with the new trend toward increasing shellside flow velocities to improve heat transfer and reduce fouling. Different flow phenomena can cause tubes to vibrate. These include vortex shedding, turbulent buffeting, fluidelastic whirling, eddy formation, and acoustic vibration. The predictive methods proposed by various investigators for the characteristic frequencies of these flow phenomena are based on tests in ideal tube banks, and they are usually not applicable to 2-phase flow. These methods when applied to the complex problem of the full-size shell-and-tube exchanger become uncertain, and a measurement of the stress state of the tubes is desirable.

This paper describes a method for assessing the reliability of tubes in the evaporator of a centrifugal water chiller and relates an actual experimental application of the proposed method.