Random excitation of heat exchangertubes by cross-flows

Abstract

This paper investigates the random excitation mechanism of tube arrays in cross-flow, also often called “turbulent buffeting”. It summarizes the experimental data obtained so far at CEA-Saclay on various tube bundles subjected to single and to two-phase flows. An attempt is made to put them into an appropriate theoretical framework. The formalism used to reduce the force spectra produced by single-phase cross-flow is first reviewed. It allows the determination of a reduced force spectrum which is found to be fairly independent of the tube array geometry. On the other hand, the situation in two-phase flow still remains insufficiently documented. Based on the restricted data set obtained at Saclay in the high void fraction range, random forces produced by air-water and by steam-water mixtures would be of the same order of magnitude. Only a crude estimate of it can be produced by using the single-phase force spectrum together with the homogeneous two-phase flow model without slip. Further investigations are still clearly required to confirm such preliminary conclusions and to derive the physically relevant scaling factors to reduce conveniently the two-phase data.