Experiment Study on Fluidelastic Instability of Tube Bundles Consisting of Different Frequency Tubes With Visual Image Processing System

Abstract

Fluidelastic instability (FEI) is the most harmful vibration mechanism for heat exchangers. Due to the inevitable manufacturing precision and assembly error, natural frequencies of tubes are not equal in the ideal condition. In order to describe the dispersion characteristic of tube bundles, a new factor named dispersion ratio is proposed in this paper. A series of tubes experiments in normal square and rotated triangular array with pitch ratio s = 1.4 and s = 1.28 were designed and conducted with high-speed camera and visual image processing system. Results show that FEI behaviors of tubes were greatly affected by tubes array geometry, pitch ratio, and dispersion ratio. Reduced critical velocity (Vcr) increased with dispersion ratio in normal square array but no obvious phenomenon was observed in rotated triangular array.