Investigation of Characteristics of Gas-Liquid Two-Phase Flows in a Rectangular Microchannel With Return Bends

2011 ◽  
Author(s):  
Akimaro Kawahara ◽  
Michio Sadatomi ◽  
Hideki Matsuo ◽  
Satoshi Shimokawa
Keyword(s):  
Void Fraction ◽  
Scaling Law ◽  
Bubble Velocity ◽  
Liquid Slug ◽  
Two Phase Flows ◽  
Two Phase ◽  
Rectangular Microchannel ◽  
Drift Flux Model ◽  
Bubble Length ◽  
Length Data

Gas-liquid two-phase flows in a horizontal rectangular microchannel with return bends have been investigated. The width and the depth of the microchannel are 240 μm and 230 μm, respectively. T-junction type gas-liquid mixer was used to introduce gas and liquid in the channel. In order to know the effects of liquid properties, distilled water, pure ethanol, 49wt% ethanol aqueous solution and HFE7200 were used as the test liquids, while nitrogen gas as the test gas. The flow pattern, the bubble velocity, the bubble length and the liquid slug length were measured, and the void fraction was determined as the ratio of the gas superficial velocity to the bubble velocity. The bubble velocity at a downstream position from the bend is faster than that at an upstream position, and thus the void fraction is smaller at a downstream position. The bubble velocity data were well correlated with the well-known drift flux model with Kawahara et al.’s distribution parameter correlation. The bubble length data at the upstream and the downstream positions are also correlated with the scaling law proposed by Garstecki et al., irrespective of the test liquids. The liquid slug length data are correlated with an exponential function of the void fraction. The ratio of the bubble length to the bubble pitch is also well correlated with a linear function of the homogeneous void fraction.

Characteristics of Two-Phase Flows in a Rectangular Microchannel With a T-Junction Type Gas-Liquid Mixer

2009 ◽  
Author(s):  
Akimaro Kawahara ◽  
Michio Sadatomi ◽  
Keitaro Nei ◽  
Hideki Matsuo ◽  
Takatoshi Masuda
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Bubble Velocity ◽  
Velocity Data ◽  
Two Phase Flows ◽  
Two Phase ◽  
Rectangular Microchannel ◽  
Drift Flux Model ◽  
Junction Type ◽  
Bubble Length

In this study, gas-liquid two-phase flows in a horizontal rectangular microchannel have been investigated. The rectangular microchannel has the hydraulic diameter of 0.235 mm, and the width and the depth of 0.24 mm and 0.23 mm, respectively. A T-junction type gas-liquid mixer was used to introduce gas and liquid in the channel. In order to know the effects of liquid properties, distilled water, ethanol and HFE7200 were used as the test liquids, while nitrogen gas as the test gas. The flow pattern, the bubble length, the liquid slug length and the bubble velocity in two-phase flow were measured with a high speed video camera, and the void fraction was determined from the bubble velocity data and the superficial gas velocity data. In addition, the pressure drop was also measured with a calibrated differential pressure transducer. The bubble length data were compared with the calculation by the scaling law proposed by Garstecki et al (2006). The bubble velocity data and/or the void fraction data were well correlated with the well-known drift flux model (Zuber and Findlay, 1965) with a new distribution parameter correlation developed in this study. The frictional pressure drop data were also well correlated with Lockhart-Martinelli method with a correlation of two-phase friction multiplier.

Gas Void Fraction Prediction for Air-Water and Air-Oil Two-Phase Flows via Artificial Neural Network

2019 ◽  
Author(s):  
Tiago Ferreira Souza ◽  
Caio Araujo ◽  
Maurício Figueiredo ◽  
FLAVIO SILVA ◽  
Ana Maria Frattini Fileti
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Void Fraction ◽  
Two Phase Flows ◽  
Two Phase ◽  
Artificial Neural ◽  
Gas Void Fraction

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.

Void fraction prediction in two-phase flows independent of the liquid phase density changes

2014 ◽  
Vol 68 ◽  
pp. 49-54 ◽  
Author(s):  
E. Nazemi ◽  
S.A.H. Feghhi ◽  
G.H. Roshani
Keyword(s):  
Liquid Phase ◽  
Void Fraction ◽  
Two Phase Flows ◽  
Two Phase ◽  
Phase Density

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.

Zuber-Type Parameter Distributions for Non-Equilibrium Two-Phase Flows: Generalization for Annular Channel and Rod Cluster Geometries

2013 ◽  
Author(s):  
Y. Kornienko
Keyword(s):  
Current Method ◽  
Annular Channel ◽  
Elementary Functions ◽  
Two Phase Flows ◽  
Principle Of Superposition ◽  
Two Phase ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Cross Section Profile ◽  
Non Equilibrium

This study presents the main results of the analysis of the previously developed generalized hierarchical closed system of analytical closure relations for the distribution parameters (DPs) Cks (k = f - fluid or g - vapor; s = 0,1,2,3 - mass, energy, momentum) that are used in quasi-one-dimensional form of the conservation laws for mass, momentum and energy in non-equilibrium two-phase flows. The current method has been expanded to account for non-uniform in cross-section profile of void fraction. The main assumptions of the received quadrature relationships for DP are: (a) the use of the drift flux model, (b) the quasi-steady-state approximation, and (c) the power-mode approximations of the local distribution profiles of the variables. These DPs Cks quadrature are expressed in terms of elementary functions, they directly reflect the principle of superposition, generalize and unify not only the Zuber-Findlay method, but also Hancox-Nicoll and Hibiki-Ishii methods. The revealed complementarity properties are particularly useful for the purposes of testing, validating and verifying DPs.

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