Modern tube and shell heat exchangers designed with the existing standards may be susceptible to damage as a result of excessive tube vibrations caused by the shell-side flow. The present study was undertaken to further our understanding of the liquid cross-flow-induced vibrations of a tube array of contemporary interest. An experimental facility to study these phenomena was designed and built. The experiments were conducted using this specially designed water tunnel having a 305 x 305 mm working section. The tube bundle was a parallel-triangular array with pitch to diameter ratio of 1.375. The array was 6 rows deep with 5 tubes in each row. Ten tubes at the centre of the array were designed to be flexibly mounted. The natural frequency and damping of these tubes could be controlled over a range of values. The rest of the tubes were rigidly fixed in the test section. The critical velocity for instability of tubes located in the third and fourth rows was established and the stability for the array was determined. The present results indicate that extrapolation of the stability boundary proposed from results obtained in wind tunnels, for arrays of the same geometry yield unconservative predictions. A study of the flow velocity power spectra indicate that no flow periodicity could be detected in the flow before the critical velocity was reached. Detuning of adjacent tubes was proven to have little effect on the stability threshold of a tube located in the third row. The results of the present study were compared with data in the published literature. It is seen that the present results lie below the majority of the proposed stability boundaries.

Master of Engineering (ME)