Flow-induced Vibration Damage Research Articles

Computational fluid dynamics investigation of thermal–hydraulic characteristics for a steam generator with and without tube support plates

A three-dimensional computational fluid dynamics model with the thermal phase change model is used to investigate the thermal–hydraulic characteristics of a steam generator with and without quatrefoil tube support plates. The two types of modeled designs are a unit pipe with and one without tube support plates. The computational fluid dynamics simulations capture the boiling phenomena, vortex and recirculation distributions, and the periodic characteristics of the circumferential wall temperature in the regions surrounding the tube support plates. The cross-flow energy responsible for flow-induced vibration damage in the region of the U-bend tubes is obtained with the aid of these localized thermal–hydraulic distributions. A comparison between the key parameters of the unit pipe models with and without tube support plates clearly reveals the influence of tube support plates in guiding flow behavior and alleviating flow-induced vibration damage for a steam generator’s U-bend tube bundle. Therefore, this computational fluid dynamics model can provide technical support for optimizing tube support plate design and improving the thermal–hydraulic characteristics of steam generator.

Numerically investigating the influence of tube support plates on thermal-hydraulic characteristics in a steam generator

A three-dimensional “unit pipe” model coupled with broached tube support plates (TSPs) is developed to investigate the influence of TSPs on the thermal-hydraulic characteristics of the primary and secondary side of steam generator (SG). The model reasonably captures the unbalanced boiling phenomena in the SG secondary side, particularly in the regions surrounding the TSPs. At these points, there is an abrupt increase in secondary fluid velocity, generating recirculation distribution and local vortex. Nonuniform outer wall temperatures periodically fluctuate around the circumference of the tubes at the TSPs, with the corresponding temperature difference between the support location and flow hole gradually decaying in the primary flow direction. These thermal-hydraulic distributions are then used to determine the cross-flow energy, which is strongly related to flow-induced vibration (FIV) damage. According to the FIV distributions, FIV damage is predicted to be most severe at angles of θ = 65° on the cold-leg side and θ = 120° on the hot-leg side of the U-bend tube bundles. These simulated FIV damage results are in agreement with the measured plant data from a prototypical SG. Therefore, this developed “unit pipe” model can provide technical support to help alleviate FIV damage and minimize the probability of tube failure.

An experimental investigation on the critical heat flux enhancement by mechanical vibration in vertical round tube

In order to gain an understanding of the relationship between critical heat flux (CHF) and flow-induced vibration (FIV), an experimental investigation was carried out with vertical round tube at the atmosphere. In the both condition of departure from nucleate boiling (DNB) and the liquid film dryout (LFD), CHF increases up to 12.6% with vibration intensity, represented by vibrational Reynolds number ( Re v). CHF enhancement by tube vibration seems to come from the reinforced flow turbulent mixing and the increment of deposition of droplet into the liquid film. Based on the experimental results, an empirical correlation is proposed for the prediction of CHF enhancement ratio. The correlation predicts the CHF enhancement ratio ( E n ) with reasonable accuracy, with an average error rate of 4.5 and 26.5% for RMS. Vibration is an effective method for heat transfer enhancement as well as CHF. Nonetheless, the risk of system failure by FIV has made it very difficult to take advantage of vibration in heat transfer facilities. Therefore, it is necessary to find out optimal fuel design enhancing the CHF but preventing FIV damage in an acceptable vibration range.

Thermal-Hydraulic Simulation of Localized Flow Characteristics in a Steam Generator

Multidimensional thermal-hydraulic characteristics in the secondary side of a steam generator (SG) are simulated by way of flow-boiling models. These models essentially belong to the so-called first-principle models that are derived from the conservation laws. The calculated results can provide the whole picture of thermal-hydraulic phenomena and the localized distributions of velocity, pressure, enthalpy, and void fraction, etc. in the secondary side of the SG. In addition, with the help of these localized flow characteristics, the forcing sources can be estimated for predicting flow-induced vibration (FIV) damage suspected in the tube bundles around the U-bend region. These calculated results can provide important information to help the FIV prediction for SG U-tubes and to find where the most possible FIV damage is located.