Abstract: Fluid-elastic instability of tube bundles is the main cause of vibration failure of heat exchangers. To establish more reasonable and reliable design guidelines for fluid-elastic instability of tube bundles subjected to two-phase cross flow, we investigated experimentally the effects of the flow conditions of the two-phase flow and the geometrical characteristics of the tube bundles on damping, vibration, and fluid-elastic instability. Moreover, we proposed recommended values of the instability constant based on the conductivity difference measurement (CDM) model and the classification of tube bundle arrangements. The reliability of these values was also verified. The results indicated that the damping ratio in the lift direction was smaller than that in the drag direction and fluid-elastic instability was more prone to occur. The order of stability of the four tube bundle arrangements from high to low was normal triangular, normal square, rotated square, and rotated triangular. Thus, to avoid fluid-elastic instability, the normal triangular tube bundle is recommended for large shell-and-tube heat exchangers subjected to two-phase cross flow. In addition, for normal square and normal triangular tube bundles, the recommended instability constant is 4.0. For rotated square and rotated triangular tube bundles, the recommended instability constant is 1.1 when the mass damping parameter is less than or equal to 0.54, otherwise the value is 1.5.

Key words: Tube bundle; Fluid-elastic instability; Two-phase cross flow; Design guidelines

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