Displaceable baffle for a heat exchanger and method for reducing vibration for the same

Abstract

A tube bundle device having at least one displaceable baffle which supports the tubes in the bundle device is disclosed in order to reduce tube vibration. The displaceable baffle includes at least two displaceable portions, which can be moved to installed position such that tubes in a tube bundle are deflected.

Description

FIELD OF THE INVENTION[0001]This invention relates to tube bundle devices such as heat exchangers, condensers and similar fluid-handling equipment with collections of tubes or rod-like elements, for example, in devices such as nuclear reactors, chemical reactors, electrical heaters, or any collection of parallel cylindrical shapes that has a fluid flow passing over the tubes or other elements. In particular, the present invention relates to a displaceable baffle or support structure for use in connection with the bundle to provide support to the individual tubes within the bundle and reduce vibration. The present invention is also directed to a method for reducing vibration in a tube bundle in a heat exchanger.BACKGROUND OF THE INVENTION[0002]Tube bundle equipment such as shell and tube heat exchangers and other similar fluid handling devices such as flow dampers and flow straighteners utilize tubes organized in bundles to conduct the fluids through the equipment. In such tube bundl...

AI Technical Summary

Benefits of technology

[0013]In accordance with another aspect of the present invention, the displaceable support baffle is used in conjunction with at least one fixed baffle. Each fixed baffle having a plurality of apertures that are sized to receive at least one of the tubes therethrough. The at least one fixed baffle and the at least one displaceable support baffle are spaced along the longitudinal axis of the tube bundle. Preferably, each displaceable support baffle is spaced from an adjacent fixed baffle. With such an arrangement when the displaceable support baffles are located in their second installed position, the tubes are deflected a sufficient amount such that the tubes also contact the fixed baffle further stabilizing the tubes within the bundle and reducing vibration.

Problems solved by technology

A common limiting factor experienced when evaluating the increase of rates in a heat exchanger is the potential for flow-induced vibration damage of the tubes.

Fluid flow patterns around the tubes may give rise to flow-induced vibrations of an organized or random oscillatory nature in the tube bundle and in the case of devices such as heat exchangers in which heat transfer takes place between the tubes and the surrounding fluid, the changes in the velocity, temperature and density of the fluid as it circulates and flows around the tubes may increase the likelihood of vibration.

If these vibrations reach certain critical amplitudes, damage to the bundle may result.

Tube vibration problems may be exacerbated if the heat exchanger equipment is retubed with tubes of a different material to the original tubes, for example, if relatively stiff materials are replaced with lighter weight tubes.

Flow-induced vibration may also occur when equipment is put to more severe operating demands, for example, when other existing equipment is upgraded and a previously satisfactory heat exchanger, under new conditions, becomes subject to flow-induced vibrations.

Rod baffle exchangers, however, tend to be approximately 30 to 40% more expensive than conventional shell-and-tube exchangers and there have been situations where tube bundle devices of this kind have failed owing to flow-induced vibrations.

If the rods are slightly oversized, tube loading will be very difficult and expensive.

Increasing baffle spacing is usually not an attractive option, since increased baffle spacing increases the likelihood of flow-induced tube vibration occurrence.

This, however, is even more expensive than the rod baffle design.

Like the rod baffle, the eggcrate is also susceptible to tube chatter that could lead to tube failure.

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