Abstract
Flow-induced vibrations in heat exchanger tubes have led to numerous accidents and economic losses in the past. Fluidelastic instability is the most critical flow-induced vibration mechanism in heat exchangers. Both experimental and computational studies conducted to determine fluidelastic instability were presented in this paper. In the experiment, a water channel was built, and a closely packed normal square tube array with a pitch-to-diameter ratio of 1.28 was tested, and significant fluidelastic instability was observed. A numerical model adopting large-eddy simulation and moving mesh was established using ANSYS CFX, and results showed good agreement with the experimental findings. The vibration behaviors of fluidelastic instability were discussed, and results showed that the dominant vibration direction of the tubes changed from streamwise to transverse beyond a critical velocity. A 180° phase lag between adjacent tubes was observed in both the experiment and simulations. Normal and rotated square array cases with pitch-to-diameter ratios of 1.28 and 1.5 were also simulated. The results of this study provide better insights into the vibration characteristics of a square tube array and will help improve the fundamental research and safety design of heat exchangers.
Highlights
Fluidelastic instability is considered the most critical flowinduced vibration mechanism in tube and shell heat exchangers that can cause short-term failure of tubes
The dominant frequency determined by the simulation agrees well with that obtained from the experiment, which verifies the reliability of the proposed simulation method in investigating the characteristics of fluidelastic instability
This paper investigated some characteristics of fluidelastic instability in square tube arrays using both experimental and numerical methods
Summary
Fluidelastic instability is considered the most critical flowinduced vibration mechanism in tube and shell heat exchangers that can cause short-term failure of tubes. Such failures are often expensive and potentially dangerous. Fluidelastic instability results from coupling between fluid-induced dynamic forces and the motion of structures. Instability occurs when the flow velocity is sufficiently high so that the energy absorbed from the fluid forces exceeds the energy dissipated by damping. Fluidelastic instability usually leads to excessive vibration amplitudes. The minimum velocity at which instability occurs is called the critical velocity. To ensure the safety of facilities, the operating flow velocity should be strictly controlled below the critical velocity
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