Experimental visualization of two-phase flow patterns and transition from stratified to slug flow

2010 ◽  
Vol 225 (2) ◽  
pp. 382-389 ◽  
Author(s):  
M J Vaze ◽  
J Banerjee
Keyword(s):  
Reynolds Number ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Dominant Role ◽  
Thermal Characteristics ◽  
Air Entrainment ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Regime Map

The transition from stratified to slug flow generates oscillations in pressure and flowrates. Large liquid surges associated with slug flow are detrimental to the operation of process equipments involving two-phase flow. The characterization of two-phase flow regimes and their transition is thus an important area of research. In the present work, flow patterns for various regimes of air—water two-phase flow are captured experimentally. A flow pattern map is established based on the visualized images. The developed flow regime map is compared with that obtained by Ghajar and Tang. Slug frequency is recorded for a variety of superficial Reynolds number to show the instances of impact pressure. The development of slug and transition to slug flow from stratified flow are analysed using these captured images. It is observed that slug becomes highly chaotic with dispersion of air bubbles, when gas superficial Reynolds number is increased for a fixed value of liquid superficial Reynolds number. For lower gas superficial Reynolds number, the slug is observed to be very clear (without air entrainment). This is true for higher value of liquid superficial Reynolds number as well. The air entrainment increases with increasing gas superficial Reynolds number. This air entrainment might play a dominant role in deciding the flow and thermal characteristics of such two-phase flows.

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.

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.

scholarly journals Slug Flow Hydrodynamics Modeling for Gas–Liquid Two-Phase Flow in a Pipe

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 533
Author(s):  
Huishu Liu ◽  
Jimiao Duan ◽  
Kecheng Gu ◽  
Jiang Li ◽  
Hao Yan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Close Contact ◽  
Liquid Droplet ◽  
Flow Patterns ◽  
Phase Flow ◽  
Interface Model ◽  
Two Phase ◽  
Model Calculations

Gas–liquid flow in a pipeline is a very common. Slug two-phase flow is dominated in the case of slightly upward flow (+0.25°) and considered to be the comprehensive flow configuration, and can be in close contact with all the other flow patterns. The models of different flow patterns can be unified. Precise prediction of the slug flow is crucial for proper design and operation. In this paper, we develop hydrodynamics unified modeling for gas–liquid two-phase slug flow, and the bubble and droplet entrainment is optimized. For the important parameters (wall and interfacial friction factors, slug translational velocity and average slug length), the correlations of these parameters are optimized. Furthermore, the related parameters for liquid droplet and gas bubble entrainment are given. Accounting for the gas–liquid interface shape, hydrodynamics models, i.e., the flat interface model (FIM) and the double interface model (DIM), of liquid film in the slug body are applied and compared with the experimental data. The calculated results show that the predictions for the liquid holdup and pressure gradient of the DIM agree with experimental data better than those of the FIM. A comparison between the available experimental results and Zhang’s model calculations shows that the DIM model correctly describes the slug dynamics in gas–liquid pipe flow.

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.

scholarly journals Application of RQA and SOM for identification of two-phase flow patterns during boiling in horizontal minichannel

2021 ◽  
Vol 321 ◽  
pp. 02008
Author(s):  
Hubert Grzybowski ◽  
Iwona Zaborowska ◽  
Romuald Mosdorf
Keyword(s):  
Pressure Drop ◽  
Liquid Flow ◽  
Slug Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Inner Diameter

In the paper, numerical methods of data analysis recurrence quantification analysis (RQA) and self-organizing map (SOM) have been used to analyse pressure drop oscillations during the flow boiling in minichannel. The performed analysis allows us to identify flow patterns based on the character of the pressure drop oscillations. The following two-phase flow patterns have been identified: liquid flow, liquid flow with small vapour bubble, slug flow, long slug flow and confined bubble flow. In the experiment, the open-loop boiling system in a circular horizontal minichannel with an inner diameter of 1 mm was investigated. The two-phase flow patterns at the outlet of the heated section were observed through the glass tube (with an inner diameter of 1 mm) and recorded by a high-speed camera Phantom v1610.

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

2009 ◽  
Author(s):  
Bofeng Bai ◽  
Maolong Liu ◽  
Xiaojie Zhang
Keyword(s):  
Experimental Study ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Experimental Parameter ◽  
Flow Patterns ◽  
Experimental Result ◽  
Phase Flow ◽  
Two Phase

An experimental study was conducted on the air-water two-phase flow patterns and pressure drop in the bed of rectangular cross section containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3mm, 6mm and 8mm) 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 occur in the experimental parameter ranges, namely bubbly flow, bubbly-slug flow, slug flow, slug-annular flow and annular flow. A correlation for bubble and slug diameter in packed beds was proposed, which is an extension of the Tung/Dhir model, Jamialahmadi’s model and Schmidt’s model. Three correlations were proposed to calculate the void friction of flow regime transition in bubble flow, slug flow and annular flow based on the bubble model in the pore region. The experimental result shows that the modified Tung and Dhir’s model of flow pattern transition is a better agreement with the experimental data compared with Tung and Dhir’s model.

scholarly journals Identification of two phase flow regimes by void fraction measurements

2005 ◽  
Vol 27 (1) ◽  
pp. 59-65
Author(s):  
Bui Dinh Tri
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Impedance Probe ◽  
Fraction Measurement

This paper will present a method to identify flow patterns (bubble & slug flow) in vertical air-water two-phase flow by void fraction measurement (using an impedance probe) at Inst. of Mechanics Hanoi.

Adiabatic Air-Water Two-Phase Flow in Circular Microchannels

2011 ◽  
Author(s):  
Aritra Sur ◽  
Dong Liu
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Phase Pressure ◽  
Circular Microchannels

Gas-liquid two-phase flow in microchannels with hydraulic diameters of 100–500 μm exhibits drastically different flow behaviors from its counterpart in conventional macroscopic channels. Two particular issues are how to determine the two-phase flow patterns and how to predict the two-phase pressure drop at given flow conditions in these microchannels. This paper presents an experimental study of adiabatic two-phase flow of air-water mixture in circular microchannels with inner diameters of 100, 180 and 324 μm, respectively, to investigate the effects of channel size and phase velocity on the two-phase flow pattern and pressure drop. The air and water superficial velocities were in the range of 0.01–120 m/s and 0.005–5 m/s. Two-phase flow patterns were visualized using highspeed photographic technique. Four basic flow patterns, namely, bubbly flow, slug flow, ring flow and annular flow, were observed. The two-phase flow maps were then constructed and the transition boundaries between different flow regimes were identified. It was found that the slug flow is the dominant two-phase flow pattern in microchannels, and the transition boundaries generally shift to regions of higher gas superficial velocities as the channel dimension decreases. The experimental measurements of two-phase pressure drop were compared to the predictions from the available two-phase models in the literature. Results show that the flow pattern-based models provide the best prediction of two-phase pressure drop in microchannels.

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