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An example of a vibration analysis for a typical heat exchanger U‐tube is illustrated in Figs. . This vibration analysis was done with the heat exchanger vibration analysis code PIPO1.

The tube support geometry and the support locations are shown in Fig. 2-20. The input data required for the PIPO1 code is outlined in Fig. 2-21. This figure shows the thermalhydraulic input in the form of pitch flow velocity distribution along the tube. Note the relatively high flow velocity in the inlet region near the tubesheet.

Fig. 2-20 Flow Velocities, Support Locations and Tube Geometry for a Typical Heat Exchanger Tube.

Fig. 2-21 Example of Heat Exchanger Tube Vibration Analysis: Input of Vibration Analysis Code PIPO1.

Typical free vibration analysis results are shown in Fig. 2-22 for selected vibration modes. The results include the vibration mode shapes and the natural frequencies.

Figure 2-23 shows the results of a fluidelastic instability analysis for the condenser tube described in Fig. 2-4. For some vibration modes, the ratio of actual to critical flow velocity for fluidelastic instability, U_p/U_pc, is greater than one, indicating that fluidelastic instability is possible for this tube, which was subjected to abnormal flow conditions. In reality, fretting‐wear and fatigue damage were observed in this condenser.

Fig. 2-22 Heat Exchanger Tube Vibration: Typical Free Vibration Analysis Results.