Simulation of the two-phase flow across tube bundle

Abstract Experiments on two-phase flow across an in-line tube bundle are analyzed with the STEG code, which has been developed for modeling thermal-hydraulic processes in a horizontal steam generator (SG). An adiabatic, vertical two-phase flows of air-water across horizontal in-line, 5 x 20 rod bundles, with a pitch-to-diameter ratio P/D=1.3 are considered, the mass velocity is varied in the range 27 - 818 kg/m2s. The calculated values of void fraction in the tube bundle are compared with the experimental ones measured by a gamma densitometer. A reasonable agreement between the calculations and the experimental data is obtained.

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Influence of the Pitch-to-Diameter Ratio on Two-Phase Flow-Induced Forces Across a Tube Bundle

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2019-93319 ◽

2019 ◽

Author(s):

Enrico Deri

Keyword(s):

Power Plants ◽

Two Phase Flow ◽

Tube Bundle ◽

Fluid Dynamic ◽

Diameter Ratio ◽

Analytical Models ◽

Phase Flow ◽

Excitation Spectra ◽

Two Phase ◽

Safety Margins

Abstract Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators and designers of nuclear power plants. In order to predict damages due to such vibrations, predictive calculations are performed, both by designers and by operators, which allow one to evaluate safety margins and thereafter to optimize the SG maintenance policy. In cases when semi analytical models of fluid-dynamic forces are used, together with corresponding dimensionless fluid force coefficients, closures are assessed by experiment. The database of dimensionless coefficients should then cover relevant tube bundle configurations. Within this framework, a test rig which was available at EDF was modified in order to arrange different pitch-to-diameter ratio bundles and different tube diameters. This paper discusses the fluid-induced forces measured on a set of flexible tubes placed in a triangular pitch bundle both in the lift and drag directions. Two-phase flow excitation spectra are presented as well.

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Two-Phase Void Fraction and Pressure Drop in Horizontal Crossflow Across a Tube Bundle

Journal of Fluids Engineering ◽

10.1115/1.2819638 ◽

1998 ◽

Vol 120 (1) ◽

pp. 140-145 ◽

Cited By ~ 14

Author(s):

G. P. Xu ◽

K. W. Tou ◽

C. P. Tso

Keyword(s):

Pressure Drop ◽

Void Fraction ◽

Mass Velocity ◽

Flow Model ◽

Tube Bundle ◽

Diameter Ratio ◽

Two Phase ◽

Friction Pressure ◽

Oil Flow ◽

Friction Pressure Drop

Void fraction and friction pressure drop measurements were made for an adiabatic, horizontal two-phase flow of air-water, air-oil across a horizontal in-line, 5 × 20 tube bundle with pitch-to-diameter ratio, P/D, of 1.28. For both air-water and air-oil flow, the experimental results showed that the average void fraction were less than the values predicted by a homogenous flow model, but were well correlated with the Martinelli parameter Xtt and liquid-only Froude number FrLO. The two-phase friction multiplier data exhibited an effect of flow pattern and mass velocity, and they could be well-correlated with the Martinelli parameter.

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Effect of Void Fraction on Vibrational Behavior of Tubes in Tube Bundle Under Two-Phase Cross Flow

Journal of Vibration and Acoustics ◽

10.1115/1.2889745 ◽

1997 ◽

Vol 119 (3) ◽

pp. 457-463 ◽

Cited By ~ 8

Author(s):

H. Y. Lian ◽

G. Noghrehkar ◽

A. M. C. Chan ◽

M. Kawaji

Keyword(s):

Void Fraction ◽

Two Phase Flow ◽

Tube Bundle ◽

Dynamic Pressure ◽

Damping Ratio ◽

Cross Flow ◽

Vibration Measurement ◽

Phase Flow ◽

Two Phase ◽

Vibrational Behavior

The effects of local two-phase flow parameters on the vibrational behavior of tubes have been studied in an in-line 5 × 20 tube bundle subjected to air-water cross-flow. One of the tubes was flexibly mounted and instrumented for vibration measurement and the others were rigid. Parameters obtained include local void fraction fluctuations, RMS amplitude of void fraction fluctuations, void fraction distributions across the tube bundle, flow regimes based on probability density function of void fraction signals, damping ratio, and tube vibration response as a function of mass flux, void fraction and dynamic pressure. Damping and tube vibration amplitude in two-phase flow have been found to be closely related to the RMS amplitudes of the local void fraction fluctuations and dynamic pressure fluctuations, respectively.

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Fluidelastic Instability and Periodic Fluid Forces in a Normal Triangular Tube Bundle Subjected to Air-Water Flow

ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B ◽

10.1115/fedsm-icnmm2010-30143 ◽

2010 ◽

Author(s):

G. Ricciardi ◽

M. J. Pettigrew ◽

N. W. Mureithi

Keyword(s):

Two Phase Flow ◽

Tube Bundle ◽

Fatigue Cracks ◽

Cross Flow ◽

Fretting Wear ◽

Phase Flow ◽

Steam Generators ◽

Two Phase ◽

Fluid Forces ◽

Void Fractions

Two-phase flow in power plant steam generators can induce tube vibrations, which may cause fretting-wear and even fatigue cracks. It is therefore important to understand the relevant two-phase flow-induced vibration mechanisms. Fluidelastic instabilities in cross-flow are known to cause the most severe vibration response in the U-bend region of steam generators. This paper presents test results of the vibration of a normal triangular tube bundle subjected to air-water cross-flow. The test section presents 31 flexible tubes. The pitch-to-diameter ratio of the bundle is 1.5, and the tube diameter is 38 mm. Tubes were flexible in the lift direction. Seven tubes were instrumented with strain gauges to measure their displacements. A broad range of void fractions (from 10% to 90%) and fluid velocities (up to 13 m/s) were tested. Fluidelastic instabilities were observed for void fractions between 10% and 60%. Periodic fluid forces were also observed. The results are compared with those obtained with the rotated triangular tube bundle, showing that the normal triangular configuration is more stable than the rotated triangular configuration.

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Comparison of Drift-Flux Models for Void Fraction Prediction in Sub-Channel of Vertical Rod Bundles

Volume 9: Student Paper Competition ◽

10.1115/icone26-81435 ◽

2018 ◽

Author(s):

Quanyao Ren ◽

Liangming Pan ◽

Wenxiong Zhou ◽

Tingpu Ye ◽

Hang Liu ◽

...

Keyword(s):

Void Fraction ◽

Drift Velocity ◽

Nuclear Reactor ◽

Two Phase Flow ◽

Rectangular Channel ◽

Phase Flow ◽

Rod Bundles ◽

Two Phase ◽

Drift Flux Model ◽

Drift Flux

In order to simulate the transfer of mass, momentum and energy in the gas-liquid two-phase flow system, tremendous work focused on the phenomenon, mechanisms and models for two-phase flow in different channels, such as circular pipe, rectangular channel, rod bundle and annulus. Drift-flux model is one of the widely used models for its simplicity and good accuracy, especially for the reactor safety analysis codes (RELAP5 and TRAC et al.) and sub-channel analysis code (COBRA, SILFEED and NASCA et al.). Most of the adopted drift-flux models in these codes were developed based on the void fraction measured in pipe and annulus, which were different with the actual nuclear reactor. Although some drift-flux models were developed for rod bundles, they were based on the void fraction on the whole cross-section not in subchannel in rod bundles due to the lack of effective measuring methods. A novel sub-channel impedance void meter (SCIVM) has been developed to measure the void fraction in sub-channel of 5 × 5 rod bundles, which is adopted to evaluate these existing drift-flux models for rod bundles. By comparison, the values of drift-flux parameters have large differences among different correlations, which are suggested to be reconsidered. Based on the experimental data and physical laws, Lellouche-Zolotar and Chexal-Lellouche correlations show a better performance for drift velocity. If the predicting error of void fraction is the only concerned parameter, Chen-Liu, Ishizuka-Inoue and Chexal-Lellouche correlations are recommended for averaged relative error less than 30%. More experiments are suggested to focus on the distribution parameter and drift velocity through their definition.

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Flow-Induced Vibration Responses of U-Tube Bundle in Air-Water Flow

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2007-26777 ◽

2007 ◽

Author(s):

In-Cheol Chu ◽

Heung June Chung ◽

Chang Hee Lee ◽

Hyung Hyun Byun ◽

Moo Yong Kim

Keyword(s):

Steam Generator ◽

Two Phase Flow ◽

Tube Bundle ◽

Damping Ratio ◽

Geometrical Parameters ◽

Phase Flow ◽

Elastic Instability ◽

Flow Induced Vibration ◽

Two Phase ◽

Vibration Responses

In the present study, a series of experiments have been performed to investigate a fluid-elastic instability of a nuclear steam generator U-tube bundle in an air-water two-phase flow condition. A total of 39 U-tubes are arranged in a rotated square array with a pitch-to-diameter ratio of 1.633. The diameter and other geometrical parameters of U-bend region are the same to those of an actual steam generator, but the vertical length of U-tubes are reduced to 2-span in contrast to 9-span of an actual steam generator. The following parameters were experimentally measured to evaluate a fluid-elastic instability of U-tube bundles in a two-phase flow: a general tube vibration response, a critical gap velocity, a damping ratio and a hydrodynamic mass. Based on the experimental measurements, the instability factor, K, of Connors’ relation was preliminary assessed with some assumptions on the velocity and density profiles of the two-phase flow.

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Development of Models Correlating Vibration Excitation Forces to Dynamic Characteristics of Two-Phase Flow in a Tube Bundle

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2007-26077 ◽

2007 ◽

Author(s):

C. Zhang ◽

M. J. Pettigrew ◽

N. W. Mureithi

Keyword(s):

Dynamic Characteristics ◽

Two Phase Flow ◽

Tube Bundle ◽

Flow Path ◽

Main Flow ◽

Phase Flow ◽

Two Phase ◽

Drag Forces ◽

Vibration Excitation ◽

Lift Forces

Recent experiments reveal that somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions existed in a rotated triangular tube bundle subjected to two-phase cross flow. The quasi-periodic drag forces appear to be related to the momentum flux fluctuations in the main flow path between the cylinders. The quasi-periodic lift forces, on the other hand, are mostly correlated to the oscillation in the wake of the cylinders. The objective of this work is to develop semi-analytical models for correlating vibration excitation forces to dynamic characteristics of two-phase flow in a rotated triangular tube bundle and understanding the nature of vibration excitation forces. The relationships between the lift or drag forces and the dynamic characteristics of two-phase flow are established through fluid mechanics momentum equations. A model has been developed to correlate the void fraction fluctuation in the main flow path and the dynamic drag forces. A second model has been developed for correlating the oscillation in the wake of the cylinders and the dynamic lift forces. Although still preliminary, each model can predict the corresponding forces relatively well.

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Experimental Investigation of Fluid-Elastic Vibration of Square Array Tube Bundle in Two Phase Flow

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2019-93473 ◽

2019 ◽

Author(s):

Ryoichi Kawakami ◽

Seinosuke Azuma ◽

Toshifumi Nariai ◽

Kazuo Hirota ◽

Hideyuki Morita ◽

...

Keyword(s):

Two Phase Flow ◽

Tube Bundle ◽

Flow Direction ◽

Phase Flow ◽

Elastic Instability ◽

Steam Generators ◽

Two Phase ◽

Critical Flow Velocity ◽

Tube Bundles ◽

Square Array

Abstract The in-plane (in-flow) fluid-elastic instability (in-plane FEI) of triangular tube arrays caused tube-to-tube wear indications as observed in the U-bend regions of tube bundles of the San Onofre Unit-3 steam generators[1]. Several researches revealed that the in-plane FEI is likely to occur in a tightly packed triangular tube array under high velocity and low friction conditions, while it is not likely to occur in a square array tube bundle. In order to confirm the potential of steam-wise fluid-elastic instability of square arrays, the critical flow velocity in two-phase flow, (sulfur hexafluoride-ethanol) which simulates steam-water flow, was investigated. Two types of test rigs were prepared to confirm the effect of the tube diameter and tube pitch ratio on the critical velocity. In both rigs, vibration amplitudes were measured in both in-flow and out-of-flow directions in various flow conditions. In any case, in-flow fluid elastic instability was not detected. Based on the results of the tests, it is concluded that the flow interaction force is small for concern to occur the fluid-elastic instability in the in-flow direction of the square tube bundles of steam generators.

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A New Capacitance Sensor for Measuring the Void Fraction of Two-Phase Flow Through Tube Bundles

Sensors ◽

10.3390/s20072088 ◽

2020 ◽

Vol 20 (7) ◽

pp. 2088

Author(s):

Wael Ahmed ◽

Adib Fatayerji ◽

Ahmed Elsaftawy ◽

Marwan Hassan ◽

David Weaver ◽

...

Keyword(s):

Void Fraction ◽

Two Phase Flow ◽

Tube Bundle ◽

Local Variation ◽

Phase Flow ◽

Capacitance Sensor ◽

Two Phase ◽

Element Analysis ◽

Tube Bundles ◽

The Stability

Evaluating the two-phase flow parameters across tube bundles is crucial to the analysis of vibration excitation mechanisms. These parameters include the temporal and local variation of void fraction and phase redistribution. Understanding these two-phase parameters is essential to evaluating the stability threshold of tube bundle configurations. In this work, capacitance sensor probes were designed using finite element analysis to ensure high sensor sensitivity and optimum response. A simulation-based approach was used to calibrate and increase the accuracy of the void fraction measurement. The simulation results were used to scale the normalized capacitance and minimize the sensor uncertainty to ±5%. The sensor and required conditioning circuits were fabricated and tested for measuring the instantaneous void fraction in a horizontal triangular tube bundle array under both static and dynamic two-phase flow conditions. The static calibration of the sensor was able to reduce the uncertainty to ±3% while the sensor conditioning circuit was able to capture instantaneous void fraction signals with frequencies up to 2.5 kHz.

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