Experimental study on cross flow induced vibration response of four-span straight tube bundle with TSP or AVB supports

Abstract

Flow induced vibrations in steam generator and other heat exchangers can result in tube failure and lead to large economic losses. Tube supports such as tube support plates (TSP) or anti-vibration bars (AVB) are commonly used to suppress the flow induced vibration. Knowledge on the tube dynamic characteristics and instability phenomena under these support conditions is therefore essential, when fluid flows across the multi-span tubes. In this paper, flow induced vibration of a four-span rotated triangular tube array with a pitch-to-diameter ratio of 1.4 under three sets of AVB or TSP supports is experimentally studied. Part of the middle segment of the tube is subjected to cross flow. The vibration displacements and frequency spectra of a tube on first row are analyzed. It was found that the vibration mode for four-span tube bundle with TSP is different from that of the tube supported by AVB when fluid elastic instability (FEI) happens. The effective FEI critical velocities for the tube with TSP and that with AVB is 6.8 m/s and 3.0 m/s, respectively. Five correlations for predicting the onset of FEI of the tube bundle tested are compared with experimental results. Weaver and El-Kashlan correlation (1981b) is best. The effective FEI critical velocities predicted by Weaver and El-Kashlan correlation (1981b) are 15% and 27% higher than the experimental results for tube with TSP and tube with AVB, respectively. The vortex shedding responses are analyzed for the two tube-support structures. The Strouhal number for non-resonant vortex shedding response is calculated and compared with expectations from literature. The turbulent buffeting response for tube under different supports are compared with each other and discussed.