Velocity distribution and vibration excitation in tube bundle heat exchangers

Design criteria for tube bundle heat exchangers, to avoid fluidelastic inst ability, are based on stability criteria for ideal bundles and uniform flow conditions along the tube length. In real heat exchangers, a non-uniform f low distribution is caused by inlet nozzles, impingement plates, baffles an d bypass gaps. The calculation of the equivalent velocities, according to t he extended stability equation of Conners, requires the knowledge of the mo de shape and the assumption of a realistic velocity distribution in each fl ow section of the heat exchanger. It is the object of this investigation to derive simple correlations and recommendations, (1) for equivalent velocit y distributions, based on partial constant velocities, and (2) For the calc ulation of the critical volume flow in practical design applications. With computational fluid dynamic (CFD) programs it is possible to calculate the velocity distribution in real tube bundles, and to determine the most endan gered tube and thereby the critical volume flow. The paper moreover present s results and design equations for the inlet section of heat exchangers wit h variations of a broad range of geometrical parameters, e.g., tube pitch, shell diameter, nozzle diameter, span width, distance between nozzle exit a nd tube bundle. (C) 2000 Editions scientifiques et medicales Elsevier SAS.