The Effects of Inlet Geometry and Gas-Liquid Mixing on Two-Phase Flow in Microchannels

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
M. Kawaji ◽  
K. Mori ◽  
D. Bolintineanu
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Internal Diameter ◽  
Inlet Section ◽  
Phase Flow ◽  
Two Phase ◽  
Inlet Geometry

The effects of gas-liquid inlet geometry and mixing method on adiabatic gas-liquid two-phase flow in a microchannel of 100 μm diameter have been investigated using a T-junction inlet with the same internal diameter as the microchannel. Two-phase flow patterns, void fraction, and friction pressure drop data obtained with the T-junction inlet were found to be significantly different from those obtained previously with a reducer inlet. For the T-junction inlet, the two-phase flow patterns in the microchannel were predominantly intermittent flows with short gas and liquid plugs/slugs flowing with nearly equal velocities. The void fraction data then conformed nearly to that of a homogeneous flow model, and the two-phase friction multiplier data could be described by the Lockhart–Martinelli correlation applicable to larger channels. However, when a reducer inlet was used previously and the diameter of the inlet section was much larger than that of the microchannel, an intermittent flow of long gas slugs separated by long liquid slugs became prevalent and the void fraction decreased to values far below the homogeneous void fraction. The differences in the two-phase flow characteristics between a T-junction inlet and reducer inlet were attributed to the differences in the gas bubble/slug generation mechanisms.

Flow Characteristics of Adiabatic Gas-Liquid Two-Phase Flow in a Horizontal Flat Rectangular Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Kentaro Satonaka ◽  
Tohru Fukano
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Similar Data ◽  
Two Phase ◽  
The Mean

Experiments were performed to obtain, analyze and clarify the mean void fraction, the mean liquid holdup, and the liquid slug velocity and the air-water two-phase flow patterns in horizontal rectangular microchannels, with the dimensions equal to 1.0 mm width × 0.1 mm depth, and 1.0 mm width × 0.2 mm depth, respectively. The flow patterns such as bubble flow, slug flow and annular flow were observed. The microchannel data showed similar data patterns compared to those in minichannels with the width of 1∼10mm and the depth of 1mm which we had previously reported on. However, in a 1.0 × 0.1 mm microchannel, the mean holdup and the base film thickness in annular flow showed larger values because the effects of liquid viscosity and surface tension on the holdup and void fraction dominate. The remarkable flow characteristics of rivulet flow and the flow with a partial dry out of the channel inner wall were observed in slug flow and annular flow patterns in the microchannel of 0.1 mm depth.

Void Fraction, Pressure Drop, and Flow Pattern Behavior for Two-Phase Non-Newtonian Slug Flow

2021 ◽  
Author(s):  
Faraj Ben Rajeb ◽  
Syed Imtiaz ◽  
Yan Zhang ◽  
Amer Aborig ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Regime ◽  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase

Abstract Slug flow is one of the most common flow patterns in non-Newtonian two-phase flow in pipes. It is a very common occurrence in gas-liquid two-phase flow in the pipe. Usually, it is an unfavorable flow pattern due to its unsteady nature, intermittency as well as high pressure drop. The differences between slug flow and elongated bubble flow are not clear because usually these two types of flow combined under one flow category. In general, these two-phase flow regimes are commonly defined as intermittent flow. In the present study, pressure gradient, and wave behavior in slug flow have been investigated depending on experimental work. In addition, void fraction has been estimated regarding available superficial liquid and gas velocities. The experimental records of superficial velocities of gas and liquid for slug flow and other flow patterns is used to create flow regime map for the gas non-Newtonian flow system. The effect of investigated flow regime velocities for non-Newtonian/gas flow on pressure drop and void fraction is reported. Pressure drop has been discovered to be reduced in slug flow more than other flow patterns due to high shear thinning behavior.

Effect of Wetting on Adiabatic Gas-Liquid Two-Phase Flow in a Microchannel

2008 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Kazuki Inoue ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Video Camera ◽  
Internal Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Friction Pressure Drop ◽  
Sensor Signals

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in wetting and poorly wetting circular microchannels of 100 μm diameter. By examining the optical sensor signals from which void fraction and the lengths and velocities of gas slugs and liquid slugs were measured, the effects of wetting on the adiabatic two-phase flow characteristics of nitrogen gas and water were investigated. The data were obtained using a T-junction with the same internal diameter as the microchannel, but the T-junction itself was well wetting in both experiments. Besides the flat nose and tail of gas plugs/slugs at low gas and liquid flow rates, poorly wetting microchannel showed higher void fraction and friction pressure drop compared to the well-wetting microchannel. The poorly wetting microchannel also showed the presence of short and fast moving liquid slugs which were absent in well-wetting microchannel.

Effect of Channel Wetting Properties on Flow Characteristics of Gas-Liquid Two-Phase Flow in a Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Video Camera ◽  
Internal Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Wetting Properties ◽  
Friction Pressure Drop

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in wetting and poorly wetting circular microchannels of 100 μm diameter. By examining the optical sensor signals from which void fraction and the lengths and velocities of gas slugs and liquid slugs were measured, the effects of wetting on the adiabatic two-phase flow characteristics of nitrogen gas and water were investigated. The data were obtained using a T-junction with the same internal diameter as the microchannel, but the T-junction itself was well wetting in both experiments. Besides the flat nose and tail of gas slugs at low gas and liquid flow rates, poorly wetting microchannel showed higher void fraction and friction pressure drop compared to the well wetting microchannel. The poorly wetting microchannel also showed the presence of short and low moving liquid slugs which were absent in well-wetting microchannel.

Effect of Inlet Geometry on Adiabatic Gas-Liquid Two-Phase Flow in a Microchannel

2007 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Internal Diameter ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Gas Volume ◽  
Compressible Gas

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in a circular microchannel of 100 μm diameter. By cross correlating the signals from two pairs of optical fibers and infrared photodiodes, void fraction and the lengths and velocities of gas slugs and liquid slugs were measured. The data were obtained using a T-junction with the same internal diameter as the microchannel but the lengths of the gas and liquid injection lines between the T-junction and flow control valves were quite different. The presence of a large compressible gas volume upstream of the T-junction had a significant effect on the two-phase flow characteristics in the microchannel, typified by the void fraction data. The two-phase flow characteristics in the absence of a compressible gas volume were analysed to obtain the liquid slug length and velocity data. The liquid slug velocity was found to be dependent on the slug length, since longer slugs experienced greater friction effects and moved with much slower velocities than the shorter liquid slugs.

Two-Phase Flow Through Square and Circular Microchannels—Effects of Channel Geometry

2004 ◽  
Vol 126 (4) ◽  
pp. 546-552 ◽  
Author(s):  
Peter M.-Y. Chung ◽  
Masahiro Kawaji ◽  
Akimaro Kawahara ◽  
Yuichi Shibata
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Geometry ◽  
Frictional Pressure Drop ◽  
Channel Shape

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 μm square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 μm circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

Two-Phase Flow Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation

2007 ◽  
Author(s):  
Sujin Yeom ◽  
Seung S. Lee ◽  
Sang Yong Lee
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Gas Pressure ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Micro Bubble

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.

Evaluation of Void Fraction Correlations for the Statistical and Numerical Analysis of Two-Phase Flows Inside Producing Geothermal Wells

2008 ◽  
Author(s):  
A. A´lvarez del Castillo ◽  
E. Santoyo ◽  
O. Garci´a-Valladares ◽  
P. Sa´nchez-Upton
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Temperature Gradients ◽  
Production Performance ◽  
Phase Flow ◽  
Two Phase ◽  
Precise Knowledge ◽  
Geothermal Wells ◽  
Gas Void Fraction

The modeling of heat and fluid flow inside two-phase geothermal wells is a vital task required for the study of the production performance. Gas void fraction is one of the crucial parameters required for a better prediction of pressure and temperature gradients in two-phase geothermal wells. This parameter affects the correct matching between simulated and measured data. Modeling of two-phase flow inside wells is complex because two phases exist concurrently (exhibiting various flow patterns that depend on their relative concentrations, the pipe geometry, and the mass flowrate). A reliable modeling requires the precise knowledge of the two-phase flow patterns (including their transitions and some flow parameters). In this work, ten empirical correlations were used to estimate the gas void fraction in vertical-inclined pipes, and to evaluate their effect on the prediction of two-phase flow characteristics of some Mexican geothermal wells. High quality downhole pressure/ temperature logs collected from four producing geothermal wells were studied [Los Azufres, Mich. (Az-18); Los Humeros, Pue. (H-1), and Cerro Prieto, B.C. (M-90 and M-201)]. The pressure/ temperature gradients were simulated using an improved version of the wellbore simulator GEOPOZO, and the gas void fraction correlations. The simulated results were statistically compared with measured field data.

scholarly journals Flow Patterns Transition Law of Oil-Water Two-Phase Flow under a Wide Range of Oil Phase Viscosity Condition

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Wei Wang ◽  
Wei Cheng ◽  
Kai Li ◽  
Chen Lou ◽  
Jing Gong
Keyword(s):  
Two Phase Flow ◽  
Stratified Flow ◽  
High Viscosity ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Neutral Stability ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range ◽  
Oil Water

A systematic work on the prediction of flow patterns transition of the oil-water two-phase flows is carried out under a wide range of oil phase viscosities, where four main flow regimes are considered including stratified, dispersed, core-annular, and intermittent flow. For oil with a relatively low viscosity, VKH criterion is considered for the stability of stratified flow, and critical drop size model is distinguished for the transition of o/w and w/o dispersed flow. For oil with a high viscousity, boundaries of core-annular flow are based on criteria proposed by Bannwart and Strazza et al. and neutral stability law ignoring that the velocity of the viscous phase is introduced for stratified flow. Comparisons between predictions and quantities of available data in both low and high viscosity oil-water flow from literatures show a good agreement. The framework provides extensive information about flow patterns transition of oil-water two-phase flow for industrial application.

Two-Phase Flow-Induced Forces on Piping in Vertical Upward Flow: Excitation Mechanisms and Correlation Models

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
M. Giraudeau ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Patterns ◽  
Large Momentum ◽  
Phase Flow ◽  
Upward Flow ◽  
Two Phase ◽  
Correlation Models ◽  
Wide Range

Momentum variation in two-phase flow generates significant low frequency forces, capable of producing unwanted and destructive vibrations in nuclear or petroleum industries. Two-phase flow-induced forces in piping were previously studied over a range of diameters from 6 mm to 70 mm in different piping element geometries, such as elbows, U-bends, and tees. Dimensionless models were then developed to estimate the rms forces and generate vibration excitation force spectra. It was found that slug flow generates the largest forces due to the large momentum variation between Taylor bubbles and slugs. The present study was conducted with a 52 mm diameter U-bend tube carrying a vertical upward flow. Two-phase flow-induced forces were measured. In addition, two-phase flow parameters, such as the local void fraction, bubble size and velocity, and slug frequency were studied to understand the relationship between the force spectra and the two-phase flow patterns. A new two-phase flow pattern map, based on existing transition models and validated using our own local void fraction measurements and force spectra, is proposed. This paper also presents a comparison of the present dimensionless forces with those of previous studies, thus covers a wide range of geometries and Weber numbers. Finally, a dimensionless spectrum is proposed to correlate forces with large momentum variations observed for certain flow patterns.

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