THE CROSSING FREQUENCY AS A MEASURE OF HEAT EXCHANGER SUPPORT-PLATE EFFECTIVENESS

• Published in: Journal of fluids and structures Vol. 16; no. 1; pp. 83 - 92
• Main Author: AU-YANG, M.K.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.01.2002; Elsevier
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Solid mechanics; Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Vibrations and mechanical waves; Level crossing; Vibration; Time frequency domain method; Heat exchanger; Dynamic stability; Critical speed; Tube plate; Fluid structure interaction; Cylinder set; Modeling; Structural analysis
• ISSN: 0889-9746; 1095-8622
• DOI: 10.1006/jfls.2001.0404

The crossing frequency is the number of times per second the vibration amplitude crosses the zero displacement line from negative displacement to positive displacement. In flow-induced vibration in which the motions are often random and/or a number of modes contribute to the vibration amplitudes, the crossing frequencies are modal-weighted average frequencies of the vibration. It is postulated in this paper that the crossing frequency can be used as a measure of heat exchanger support-plate effectiveness. Using a time-domain, nonlinear analysis technique, the crossing frequencies of a tube vibrating in support plates with oversized holes can be computed as a function of time and the tube-to-support-plate clearances. It was found that the fluid–elastic stability margin of a tube bundle, in the context of the original Connors' equation for tube bundle fluid–elastic instability, should be independent of the tube-to-support-plate clearances. A simple method of estimating the critical velocity based on the time-domain equation of fluid–elastic stability is suggested.