Calculation of a maximum permitted flow velocity to avoid vibration damage in heat exchangers

Vibration damage of heat exchanger tubes generally occurs very rapidly in the first few hours of service or, alternatively, after several years of service. The very rapid damage is caused by strong interactions between the tube vibration and the fluid cross flow, resulting in indefinitely large amplitudes of unstable vibration. The damage that occurs after several years of service is associated with wear. In this case, the interaction between the cross flow and the tube is relatively weak, but the maintenance of a constant amplitude of vibration eventually causes damage. New formulae for treating both these circumstances by an examination of the fundamental governing equation are developed. Some data that have been recently measured are poorly represented by existing theory. The implications of these recent data are discussed, and new equations are developed by performing a dimensional analysis and using some results from the theory of control systems. (author)