Adiabatic Gas-Liquid Two-Phase Flow Patterns in Microchannels

2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung
Keyword(s):  
Surface Tension ◽  
Flow Regime ◽  
Slug Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Micro Channel ◽  
Surface Tension Effect ◽  
Two Phase ◽  
Micro Channels ◽  
Churn Flow

Flow patterns of adiabatic gas-liquid two-phase flow in micro-channels were experimentally investigated. Using nitrogen and water, experiments were conducted in square micro-channels with hydraulic diameters of 0.209mm, 0.412mm and 0.622 mm, respectively. Gas and liquid superficial velocities were varied from 0.06–72.3 m/s and 0.02–7.13 m/s, respectively. Four defined flow patterns, bubbly-slug flow, slug-ring flow, dispersed-churn flow and annular flow, were observed in micro-channels of 0.412 mm and, 0.622 mm. In the micro-channel of 0.209 mm, the bubbly-slug flow became the slug-flow and the dispersed-churn flow disappeared due to the surface tension effect and the smooth gas-liquid interface. The flow regime maps for the current three micro-channels were constructed and showed the transition lines shifted to higher gas superficial velocity due to the stronger surface tension effect with a smaller channel size in micro-channels. They were also compared with some other micro-channel flow regime maps and the mini-channel flow regime map based on the Weber number model, which showed the flow map for the micro-channel is significantly sensitive to the working fluid, channel geometry and channel size and the flow regime criteria developed for mini-channels should not be applied for micro-channels without further verification.

Size Effect on Adiabatic Gas-Liquid Two-Phase Flow Map and Void Fraction in Micro-Channels

2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung
Keyword(s):  
Linear Relationship ◽  
Flow Regime ◽  
Slug Flow ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Void Fractions ◽  
Micro Channels ◽  
Mini Channels ◽  
Churn Flow

Adiabatic gas-liquid two-phase flow patterns and void fractions in micro-channels were experimentally investigated. Using nitrogen gas and water, experiments were conducted in near-square micro-channels with hydraulic diameters of 0.209mm, 0.412mm and 0.622 mm, respectively. The main objective was focused on the effects of micro-scale channel sizes. Gas and liquid superficial velocities were varied from 0.06-72.3 m/s and 0.02-7.13 m/s, respectively. Four defined flow patterns including bubbly-slug flow, slug-ring flow, dispersed-churn flow and annular flow were observed in both micro-channels of 0.412 mm and, 0.622 mm in hydraulic diameter. In the micro-channel of 0.209 mm, the bubbly-slug flow turned into the slug-flow and the dispersed-churn flow was not observed. The current flow regime maps showed that the transition lines shifted towards higher gas superficial velocity due to the stronger surface tension effect as the channel size was reduced. The micro-channel flow regime maps were found to be quite different from those of mini-channels. Measured time-averaged void fractions in our micro-channels held a non-linear relationship with the homogeneous void fraction as oppose to the relatively linear trend for the mini-channels. A new correlation was proposed to predict the non-linear relationship that fits most of the experimental data of the current three micro-channels and those of the 0.1 mm diameter tube reported by Kawahara et al. within ± 15%.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

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.

Water-Silicone Oil Two-Phase Flow Hydrodynamics in a Square Glass Microchannel

2018 ◽  
Author(s):  
Zan Wu ◽  
Astrid Svensson ◽  
Jin-yuan Qian ◽  
Bengt Sunden
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Silicone Oil ◽  
Sodium Dodecyl ◽  
Flow Patterns ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Dimensionless Numbers ◽  
Two Phase

This work visualized water-silicone oil two-phase flow patterns both at the inlet cross-junction and in the main square microchannel with a channel width of 400 μm. Tubing/threading, dripping and jetting were identified at the inlet junction while annular, slug and droplet flows were categorized in the main microchannel at 50 mm downstream of the junction. Flow patterns were represented in terms of superficial velocities and dimensionless numbers. Compared to water-silicone oil flow, addition of surfactant sodium dodecyl sulfate (SDS) in water, with a dilute SDS concentration of 1000 ppm, narrows the dripping regime and widens the jetting regime at the inlet junction, while narrows the slug flow regime and widens the droplet flow regime in the main microchannel. A decrease in dynamic interfacial tension due to SDS addition is supposed to be the reason for such a flow pattern modification. Besides, for slug flow, the slug length can be scaled as a power law of the flow rate ratio and the Capillary number of the organic phase. The slug velocity is linearly dependent on the bulk average velocity for both cases with and without SDS addition.

Numerical study on gas–liquid two-phase flow and mass transfer in a microchannel

2021 ◽  
Vol 19 (3) ◽  
pp. 295-308
Author(s):  
Jin Zunlong ◽  
Liu Yonghao ◽  
Dong Rui ◽  
Wang Dingbiao ◽  
Chen Xiaotang
Keyword(s):  
Mass Transfer ◽  
Surface Tension ◽  
Slug Flow ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Plug

Abstract A numerical study of the gas–liquid two-phase flow and mass transfer in a square microchannel with a T-junction is carried out in this work. Through numerical simulation methods, the flow patterns of bubble flow, slug flow and annular flow are determined. By proposing a new flow pattern conversion relationship with different media and different speeds, 100 sets of CO2-water flow patterns and 100 sets of CO2-ethanol flow patterns are obtained. The effects of surface tension on flow pattern, bubble length and liquid plug length are studied. The pressure distribution and pressure drop are analyzed, and mass transfer is obtained through slug flow simulation, and the influencing factors of gas–liquid mass transfer are studied. The results show that the effect of surface tension on the length of the bubble and the length of the liquid plug is completely opposite, the pressure distribution is stepped, and the pressure drop increases with the increase of the gas–liquid velocity. In addition, it was found that the volumetric mass transfer coefficients of the bubble cap and the liquid film gradually decreased with time, and eventually stabilized. The increase in bubble velocity accelerates the mass transfer rate, while the increase in unit cell length slows the mass transfer rate. However, the influence of film thickness and liquid film length on mass transfer varies with time.

Conditions for a Pipe to Run Full When Discharging Liquid Into a Space Filled With Gas

1977 ◽  
Vol 99 (2) ◽  
pp. 405-413 ◽  
Author(s):  
G. B. Wallis ◽  
C. J. Crowley ◽  
Y. Hagi
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Flow Patterns ◽  
Vertical Tube ◽  
Diameter Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Horizontal Tubes ◽  
Variable Space ◽  
Vertical Tubes

Experiments were performed with water discharging into air from horizontal and vertical tubes of several diameters. The horizontal tubes discharged into a variable space between vertical plates. The effects of length/diameter ratio and the shape of the end of the tube were investigated for the case of vertical tubes. In each case the conditions for the pipes to run full were associated with the formation and washout of large gas bubbles resembling those occurring in the slug flow regime of two-phase flow. The data for horizontal tubes were successfully correlated with some simple limiting theories and dimensionless representations. The vertical tube results were influenced by stability phenomena and nonsymmetrical flow patterns; as a result only a partial understanding was obtained.

On Instabilities in Horizontal Two-Phase Flow

1994 ◽  
Vol 59 (12) ◽  
pp. 2595-2603
Author(s):  
Lothar Ebner ◽  
Marie Fialová
Keyword(s):  
Differential Equation ◽  
Flow Regime ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Annular Flows ◽  
Flow Regime Maps

Two regions of instabilities in horizontal two-phase flow were detected. The first was found in the transition from slug to annular flow, the second between stratified and slug flow. The existence of oscillations between the slug and annular flows can explain the differences in the limitation of the slug flow in flow regime maps proposed by different authors. Coexistence of these two regimes is similar to bistable behaviour of some differential equation solutions.

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.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2004 ◽  
Vol 126 (3) ◽  
pp. 288-300 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406×2.032mm2 cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Features unique to two-phase micro-channel flow were identified and employed to validate key assumptions of an annular flow boiling model that was previously developed to predict pressure drop and heat transfer in two-phase micro-channel heat sinks. This earlier model was modified based on new findings from the adiabatic two-phase flow study. The modified model shows good agreement with experimental data for water-cooled heat sinks.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

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