Flow-Induced Void Fraction Transition Phenomenon in Two-Phase Flow

2010 ◽  
Author(s):  
Xiuzhong Shen ◽  
Kaichiro Mishima ◽  
Hideo Nakamura
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Regimes ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Transition Phenomenon ◽  
Drift Flux Model ◽  
Slug Flows

The flow-induced void fraction transition phenomenon was observed in an upward air-water two-phase flow in a vertical pipe with inner diameter D = 200 mm and height z = 25 m. As the two-phase flow develops in a vertical pipe, the void fraction increases firstly in the flow direction in bubbly flow, then decreases in the flow direction, finally increase again. The flow-induced void fraction transition shows an N-shaped changing manner. The present experimental investigation revealed that this phenomenon was attributed to the formation and the growth of local dominant large bubbles in the flow. According to the bubble sizes and behaviors observed in the experiment, the flow regimes were classified into bubbly, churn and slug flows in a vertical large-diameter pipe. The drift velocities in the three flow regimes were measured in this paper. New constitutive equation for drift velocities in bubbly, churn and slug flows was proposed and confirmed in this study. The flow-induced void fraction transition in N-shaped manner can be predicted by using the drift flux model with the newly developed constitutive equations.

Countercurrent Two-Phase Flow Regimes and Void Fraction in Vertical and Inclined Channels

1995 ◽  
Vol 119 (3) ◽  
pp. 182-194 ◽  
Author(s):  
S. M. Ghiaasiaan ◽  
K. E. Taylor ◽  
B. K. Kamboj ◽  
S. I. Abdel-Khalik
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Inclined Channels

Axial Development of Vertical Upward Bubbly Flow in a Minipipe

2005 ◽  
Author(s):  
Tatsuya Hazuku ◽  
Naohisa Tamura ◽  
Norihiro Fukamachi ◽  
Tomoji Takamasa ◽  
Takashi Hibiki ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Constitutive Relations ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Measurements ◽  
Local Flow ◽  
Interfacial Area Concentration ◽  
Drift Flux Model

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. Mechanistic modeling of the interfacial area concentration entirely relies on accurate local flow measurements over extensive flow conditions and channel geometries. From this point of view, accurate measurements of flow parameters such as void fraction, interfacial area concentration, gas velocity, bubble Sauter mean diameter, and bubble number density were performed by the image processing method at five axial locations in vertical upward bubbly flows using a 1.02 mm-diameter pipe. The frictional pressure loss was also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 1.02 m/s to 4.89 m/s and from 0.980% to 24.6%, respectively. The obtained data give near complete information on the time-averaged local hydrodynamic parameters of two-phase flow. These data can be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. As the first step to understand the flow characteristics in mini-channels, the applicability of the existing drift-flux model, interfacial area correlation, and frictional pressure correlation was examined by the data obtained in the mini-channel.

Experiment of Adiabatic Two-Phase Flow in an Annulus Under Low-Frequency Vibration

2012 ◽  
Author(s):  
Shao-Wen Chen ◽  
Caleb S. Brooks ◽  
Chris Macke ◽  
Takashi Hibiki ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Regimes ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase ◽  
Specific Flow ◽  
Low Frequency Vibration ◽  
Fft Analysis

In order to investigate the possible effect of seismic vibration on two-phase flow dynamics and thermal-hydraulics of a nuclear reactor, experimental tests of adiabatic air-water two-phase flow under low-frequency vibration were carried out in this study. An eccentric cam vibration module operated at low motor speed (up to 390rpm) was attached to an annulus test section which was scaled down from a prototypic BWR fuel assembly sub-channel. The inner and outer diameters of the annulus are 19.1mm and 38.1mm, respectively. The two-phase flow operating conditions cover the ranges of 0.03≤<jg> ≤1.46m/s and 0.25≤<jf>≤1.00m/s and the vibration displacement ranges from ±0.8mm to ±22.2mm. Steady-state area-averaged instantaneous and time-averaged void fraction was recorded and analyzed in stationary and vibration experiments. A neural network flow regime identification technique and fast Fourier transformation (FFT) analysis were introduced to analyze the flow regimes and void signals under stationary and vibration conditions. Experimental results reveal possible changes in flow regimes under specific flow and vibration conditions. In addition, the instantaneous void fraction signals were affected and shown by FFT analysis. Possible reasons for the changes include the applied high acceleration and/or induced resonance at certain ports under the specific flow and vibration conditions.

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

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.

Experimental identification of flow regimes in gas–liquid two phase flow in a vertical pipe

Meccanica ◽  
2015 ◽  
Vol 51 (8) ◽  
pp. 1771-1782 ◽  
Author(s):  
Pedram Hanafizadeh ◽  
Javad Eshraghi ◽  
Alireza Taklifi ◽  
Soheil Ghanbarzadeh
Keyword(s):  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Experimental Identification

Void fraction measurement in modeled two-phase flow inside a vertical pipe by using polyethylene phantoms

2015 ◽  
Vol 40 (44) ◽  
pp. 15206-15212 ◽  
Author(s):  
Reza Faghihi ◽  
Mohammadreza Nematollahi ◽  
Ali Erfaninia ◽  
Mahtab Adineh
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Fraction Measurement

Measurement of Void Fraction in Magnetic Fluid Using Electromagnetic Induction

2003 ◽  
Vol 125 (3) ◽  
pp. 479-485 ◽  
Author(s):  
S. Shuchi ◽  
H. Yamaguchi ◽  
M. Takemura
Keyword(s):  
Numerical Analysis ◽  
Linear Relationship ◽  
Void Fraction ◽  
Magnetic Fluid ◽  
Electromagnetic Induction ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Actual Measurement ◽  
Drift Flux Model

A new technique of measuring void fraction in magnetic fluid using electromagnetic induction was proposed. In order to establish the measuring method, a feasibility study was conducted experimentally with an aid of numerical analysis. From the results of static experiment and numerical analysis, it was obtained that there exists a linear relationship between the void fraction and the measured electromotive force, when induction coils were connected in series for Helmholtz excitation coils, regardless of distribution of air bubbles in magnetic fluid. By applying the calibrated linear relationship to actual two-phase situations, it was revealed that the proposed method yielded quite reasonable account for measuring the void fraction, showing excellent agreement with the mechanical measured data in the two-phase flow apparatus, and with the published correlation of the drift flux model. From the results of the present investigation, it was proved that the proposed technique is feasible for the actual measurement of void fraction in two-phase flow of magnetic fluid.

Experimental Investigation of Two Phase Flow in Micro-Sized Circular Tubes

2012 ◽  
Author(s):  
Y. S. Lim ◽  
Simon C. M. Yu
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Transitional Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Glass Tubes ◽  
Flux Model

Single phase and two phase flow characteristics in micro-sized glass tubes with i.d. (inner diameter) of 300 and 500 μm have been examined experimentally. Single phase pressure drop measurements are found generally in good agreement with Poiseulle flow theory. Transitional flow is found to start earlier at Reynolds number about 1600 as compared to the onset of transitional flow at Reynolds number of 2300 for macro-scale tubes. In addition, these glass tubes are employed for the investigation of adiabatic two phase flow characteristic by introducing gas phase via a stainless steel tube inserted at the center of the glass tube. Real time flow visualization obtained under the same flow condition are analyzed by both cross sectional void fraction (one dimensional drift flux model) and volumetric void fraction (image processing method). The analysis shows that the void fraction estimated by drift flux model (DFM) agrees with homogeneous correlation (α = β) and Armand correlation (α = 0.833β). However image processing method seems to reveal that the slip ratio for the two phase flow is more significant and that the void fraction results are clustering between slip ratio of 3 and 7. Additionally, two phase frictional pressure losses are compared with the convention correlation for macro-sized tube (Lockhart-Martinelli model). It is found that measurements of the two phase frictional pressure drop can serve as a flow map to predict the flow patterns when the flow in the channel is not transparent.

scholarly journals Simultaneous Measurement of Two-Phase Flow Parameters for Drift-Flux Model

2021 ◽  
Vol 39 (4) ◽  
pp. 1343-1350
Author(s):  
Tat Thang Nguyen
Keyword(s):  
Phase Velocity ◽  
Void Fraction ◽  
Simultaneous Measurement ◽  
Two Phase Flow ◽  
Measured Data ◽  
Phase Flow ◽  
Two Phase ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flux Model

The drift-flux model is widely used in study, calculation and design of two-phase flow. It is a highly efficient model that requires little computation resources. In the model, accurate calculation of the distribution parameter C0 and the drift velocity Vgj is a critically important factor. The calculation requires simultaneously measured data of phase velocity and void fraction distributions or profiles. By using currently widely used methods for two-phase flow measurement, satisfying the requirement is highly difficult. This paper presents novel results of simultaneous measurement of the phase velocity and void fraction profiles in a vertical round tube of 50 mm inner diameter. A combination measurement method has been developed. It comprises the multiwave Ultrasonic Velocity Profile (multiwave UVP) method and the Wire Mesh Tomography (WMT). Based on the measured data, C0 and Vgj have been calculated. They have been compared with those of the published experimental data and correlations. Analyses of the measured data have been carried out. For the first time, the analysis results reveal the variation of C0 and Vgj in the measured flow conditions. More importantly, the data obtained are also useful for the development and validation of the computational codes for two-phase flow.

Numerical Prediction of Cooling Capability in Hemispherical Gap Flow Passage for In-Vessel Core Retention

2002 ◽  
Author(s):  
Akihiro Uchibori ◽  
Kenji Fukuda ◽  
Koji Morita ◽  
Tatsuya Matsumoto
Keyword(s):  
Heat Flux ◽  
Void Fraction ◽  
Two Phase Flow ◽  
High Heat Flux ◽  
Phase Flow ◽  
Narrow Gap ◽  
Two Phase ◽  
Flow Passage ◽  
Drift Flux Model ◽  
Gap Flow

A numerical method for thermal hydraulic phenomena in a hemispherical narrow gap flow passage was developed to evaluate a cooling capability with gap formation between the molten core and the reactor pressure vessel.The gap cooling mechanism was modeled as gas-liquid two-phase flow in the narrow gap with two-dimensional spherical coordinate system. The analytical model is based on a modified drift flux model for multi-dimensional two-phase flow analysis. Numerical results showed that liquid phase intrusion into the gap in the counter direction of gas phase upward flow kept down a rise of void fraction as gap cooling phenomena. Under the high heat flux condition,expansion of the high void fraction region due to the counter-current flow limitation was reproduced as a dryout phenomenon. Characteristics of gap cooling limitation predicted by the numerical analyses were verified by comparison with various experimental data and correlations of critical heat flux.

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