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.

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.

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 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.

Pressure Drop and Void Fraction in Steam-Water Two-Phase Flow at High Pressure

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Wei Liu ◽  
Hidesada Tamai ◽  
Kazuyuki Takase
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Water Pressure ◽  
Homogeneous Model ◽  
Test Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Drift Flux Model

For a steam generator (SG) in a commercialized sodium-cooled fast breeder reactor (FBR), flow instability in the water side is one of the most important items needing research. As the first step of this research, thermal-hydraulic experiments using water as the test fluid were performed under high pressure conditions at the Japan Atomic Energy Agency (JAEA) by using a circular tube. Void fraction, pressure drop, and heat transfer coefficient data were obtained under 15, 17, and 18 MPa. This paper discusses the steam-water pressure drop and void fraction. Using the obtained data, we evaluated existing correlations for void fraction and two-phase flow multipliers under high pressure. As a result, the drift flux model implemented in the TRAC-BF1 code was confirmed to suitably predict the void fraction well under the present high pressure conditions. For the two-phase flow multiplier, the Chisholm correlation and the homogeneous model were confirmed to be the best under the present high-pressure conditions.

Analogy Between Heat Transfer and Fluid Friction of Gas-Liquid Two-Phase Flow in Minichannel

2003 ◽  
Author(s):  
Masuo Kaji ◽  
Toru Sawai ◽  
Koji Mori
Keyword(s):  
Heat Transfer ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Experimental Results ◽  
Stainless Steel Tube ◽  
Good Prediction ◽  
Phase Flow ◽  
Two Phase ◽  
Fluid Friction ◽  
Drift Flux Model

To investigate the analogy between heat transfer and fluid friction of two-phase flow in minichannel, heat transfer coefficient, pressure drop and void fraction were simultaneously measured for vertical upward heated air-water two-phase flow in a 2.01 mm I.D. stainless steel tube. Void fraction was slightly different from Smith’s correlation and drift flux model, but the latter gave fairly good prediction when α>0.8. Frictional pressure losses were greater than the experimental results of Mishima-Hibiki for a 2.05 mm I.D. Pyrex glass tube and the correlation of Chisholm-Laird. Heat transfer coefficients agreed with our previous experimental results for a 8.03 mm I.D. tube. A theoretical calculation was performed for an annular liquid film flow model using experimental values of wall shear stress and liquid holdup, and satisfactory results were obtained except when the liquid flow rate was very low.

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