Liquid-Liquid Flow Patterns in Microchannels

2017 ◽  
Author(s):  
Zhen Cao ◽  
Zan Wu ◽  
Mehdi Sattari Najafabadi ◽  
Bengt Sunden
Keyword(s):  
Aspect Ratio ◽  
Flow Pattern ◽  
Liquid Flow ◽  
Flow Patterns ◽  
Continuous Phase ◽  
Hydraulic Diameter ◽  
Intermittent Flow ◽  
Dimensionless Number ◽  
Dispersed Phase ◽  
Flow Pattern Map

In the present work, liquid-liquid flow patterns positioned 40 mm downstream the inlet of microchannels were experimentally investigated, including the effect of hydraulic diameter (Dh), liquid properties, aspect ratio of cross section (a) and inlet configuration. Deionized water, butanol, toluene and hexane were selected as probe fluids with water as the continuous phase. Cross-inlet microchannels of 200 μm * 200 μm (Dh = 200 μm), 400 μm * 400 μm (Dh = 400 μm), 600 μm * 600 μm (Dh = 600 μm) and 600 μm * 300 μm (Dh = 400 μm) as well as a T-inlet microchannel of 600 μm * 300 μm (Dh = 400 μm) were tested. For the tests in the microchannels of Dh = 600 μm and 400 μm, the superficial velocities of the dispersed phase and continuous phase varied between 0.3 mm/s and 12 mm/s and between 0.2 mm/s and 50 mm/s, while in the microchannel of Dh = 200 μm the superficial velocities of the dispersed phase and continuous phase ranged from 0.3 mm/s to 21 mm/s and from 0.2 mm/s to 150 mm/s. Annular flow, deformed interface flow, slug flow, intermittent flow, droplet and slug train flow and droplet flow were detected in the experiment. It shows that flow patterns depend on the hydraulic diameter, liquid properties, inlet configuration and aspect ratio significantly. Dimensionless analysis was employed to develop universal flow pattern maps regardless of the hydraulic diameter and liquid properties. It is indicated that an acceptable universal flow pattern map was derived based on the redefined dimensionless number Rei0.2 *Wei0.4, especially for the boundaries of the slug-droplet transitions, which are independent on the hydraulic diameter to some extent. The other dimensionless number Wei*Ohi worked rather effectively to develop a universal flow pattern map independent on liquid properties. The boundaries of the flow pattern transitions in different liquid-liquid flow almost overlap with each other.

scholarly journals Probabilistic approach of a flow pattern map for horizontal, vertical, and inclined pipes

2019 ◽  
Vol 74 ◽  
pp. 67 ◽  
Author(s):  
Rafael Amaya-Gómez ◽  
Jorge López ◽  
Hugo Pineda ◽  
Diana Urbano-Caguasango ◽  
Jorge Pinilla ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Gas Flow ◽  
Probabilistic Approach ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Two Phase ◽  
Flow Pattern Map ◽  
Segregated Flow ◽  
Probabilistic Flow ◽  
Inclined Pipes

A way to predict two-phase liquid-gas flow patterns is presented for horizontal, vertical and inclined pipes. A set of experimental data (7702 points, distributed among 22 authors) and a set of synthetic data generated using OLGA Multiphase Toolkit v.7.3.3 (59 674 points) were gathered. A filtering process based on the experimental void fraction was proposed. Moreover, a classification of the pattern flows based on a supervised classification and a probabilistic flow pattern map is proposed based on a Bayesian approach using four pattern flows: Segregated Flow, Annular Flow, Intermittent Flow, and Bubble Flow. A new visualization technique for flow pattern maps is proposed to understand the transition zones among flow patterns and provide further information than the flow pattern map boundaries reported in the literature. Following the methodology proposed in this approach, probabilistic flow pattern maps are obtained for oil–water pipes. These maps were determined using an experimental dataset of 11 071 records distributed among 53 authors and a numerical filter with the water cut reported by OLGA Multiphase Toolkit v7.3.3.

Effects of Inlet Arrangements on Liquid-Liquid Flow Patterns in Cross-Junction Square Microchannels

2017 ◽  
Author(s):  
Jin-Yuan Qian ◽  
Zan Wu ◽  
Zhen Cao ◽  
Bengt Sunden
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Two Phase Flow ◽  
High Surface ◽  
Scale Up ◽  
Flow Patterns ◽  
Continuous Phase ◽  
Phase Flow ◽  
Two Phase ◽  
Circular Microchannels

Due to the high surface area to volume ratios leading to intensified heat and mass transfer rates, microreactors have been subject of interest for some time. Liquid-liquid two-phase flow is a very common phenomenon in microchannels. During the scale-up using a numbering-up approach, rectangular and square microchannels are preferred to circular microchannels in terms of easier integration of the former with a less volume. Therefore, liquid-liquid two-phase flow in non-circular microchannels has been investigated recently. However, there are still gaps in the fundamental understanding of liquid-liquid two-phase flow, such as the effect of inlet junctions or arrangements on flow patterns in non-circular microchannels. The present work aims to study the effect of inlet arrangements on liquid-liquid two-phase flow dynamics and flow patterns of square glass microchannels. In this paper, oil is used as the dispersed phase and de-ionized water is used as the continuous phase. The special inlet arrangement in the cross-junction is compared to these common inlet arrangements of T-junction and cross-junction square microchannels. The effect of the inlet continuous phase velocity on the slug length is studied. Then, the slug lengths with the same inlet velocities of the three inlets and equal velocities of the two phases are carried out, respectively. Meanwhile, typical liquid-liquid flow pattern transitions are achieved at specific conditions. Finally, a special phenomenon without the droplet flow pattern is introduced, due to introduction of the novel inlet arrangement.

scholarly journals Liquid-Liquid Flow Pattern Prediction Using Relevant Dimensionless Parameter Groups

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4355
Author(s):  
Olusegun Samson Osundare ◽  
Gioia Falcone ◽  
Liyun Lao ◽  
Alexander Elliott
Keyword(s):  
Froude Number ◽  
Flow Pattern ◽  
Liquid Flow ◽  
Dimensionless Parameter ◽  
Experimental Studies ◽  
Flow Patterns ◽  
Viscous Force ◽  
Water Fraction ◽  
Flow Pattern Map ◽  
Eotvos Number

Accurate predictions of flow patterns in liquid-liquid flow are critical to the successful design and operation of industrial and geo-energy systems where two liquids are jointly transported. Unfortunately, there is no unified flow pattern map, because all published maps are based on limited ranges of dimensional parameters. Dimensional analysis was performed on oil-water horizontal flows, to obtain some relevant dimensionless parameter groups (DPG) for constructing flow pattern maps (FPM). The following combinations of DPG were used: (i) the ratio of mixture Reynolds number to Eötvös number versus water fraction, (ii) the ratio of Weber number to Eötvös number versus water fraction, (iii) the mixture Froude number versus water fraction, (iv) the water Froude number versus oil Froude number, (v) the ratio of gravity force to viscous force versus water fraction. From twelve published experimental studies, 2696 data points were gathered and analysed covering a variety of flow patterns including stratified, stratified mixed, dispersed oil in water, dispersed water in oil, annular and slug flows. Based on the performed analysis, it was found that flow patterns could occupy more than one isolated region on the DPG-based flow pattern map. None of the combinations of DPG can mark out all the considered flow patterns, however, some combinations of DPG are particularly suitable for marking out the regions associated with some flow patterns.

Energy of Intrinsic Mode Function for Gas-Liquid Flow Pattern Identification

2012 ◽  
Vol 19 (4) ◽  
pp. 759-766 ◽  
Author(s):  
Zhiqiang Sun ◽  
Hui Gong
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Average Energy ◽  
Flow Patterns ◽  
Pattern Identification ◽  
Intrinsic Mode Function ◽  
Flow Pattern Map ◽  
Mode Function ◽  
Gas Liquid Flow ◽  
Flow Pattern Identification

Abstract Gas-liquid flows abound in a great variety of industrial processes. Correct recognition of the regimes of a gasliquid flow is one of the most formidable challenges in multiphase flow measurement. Here we put forward a novel approach to the classification of gas-liquid flow patterns. In this method a flow-pattern map is constructed based on the average energy of intrinsic mode function and the volumetric void fraction of gas-liquid mixture. The intrinsic mode function is extracted from the pressure fluctuation across a bluff body using the empirical mode decomposition technique. Experiments adopting air and water as the working fluids are conducted in the bubble, plug, slug, and annular flow patterns at ambient temperature and atmospheric pressure. Verification tests indicate that the identification rate of the flow-pattern map developed exceeds 90%. This approach is appropriate for the gas-liquid flow pattern identification in practical applications.

scholarly journals Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2440
Author(s):  
Youngwoo Kim ◽  
Dae Yeon Kim ◽  
Kyung Chun Kim
Keyword(s):  
Porous Media ◽  
Flow Pattern ◽  
Flow Regime ◽  
Annular Flow ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Flow Patterns ◽  
Flow Pattern Map ◽  
Mist Flow ◽  
Churn Flow

A flow visualization study was carried out for flow boiling in a rectangular channel filled with and without metallic random porous media. Four main flow patterns are observed as intermittent slug-churn flow, churn-annular flow, annular-mist flow, and mist flow regimes. These flow patterns are clearly classified based on the high-speed images of the channel flow. The results of the flow pattern map according to the mass flow rate were presented using saturation temperatures and the materials of porous media as variables. As the saturation temperatures increased, the annular-mist flow regime occupied a larger area than the lower saturation temperatures condition. Therefore, the churn flow regime is narrower, and the slug flow more quickly turns to annular flow with the increasing vapor quality. The pattern map is not significantly affected by the materials of porous media.

Effect of Geometry on Droplet Generation in a Microfluidic T-Junction

2013 ◽  
Author(s):  
Katerina Loizou ◽  
Wim Thielemans ◽  
Buddhika N. Hewakandamby
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Main Channel ◽  
Superficial Velocity ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Aspect Ratios ◽  
The Cross

The main aim of this study is to examine how the droplet formation in microfluidic T-junctions is influenced by the cross-section and aspect ratio of the microchannels. Several studies focusing on droplet formation in microfluidic devices have investigated the effect of geometry on droplet generation in terms of the ratio between the width of the main channel and the width of the side arm of the T-junction. However, the contribution of the aspect ratio and thus that of the cross-section on the mechanism of break up has not been examined thoroughly with most of the existing work performed in the squeezing regime. Two different microchannel geometries of varying aspect ratios are employed in an attempt to quantify the effect of the ratio between the width of the main channel and the height of the channel on droplet formation. As both height and width of microchannels affect the area on which shear stress acts deforming the dispersed phase fluid thread up to the limit of detaching a droplet, it is postulated that geometry and specifically cross-section of the main channel contribute on the droplet break-up mechanisms and should not be neglected. The above hypothesis is examined in detail, comparing the volume of generated microdroplets at constant flowrate ratios and superficial velocities of continuous phase in two microchannel systems of two different aspect ratios operating at dripping regime. High-speed imaging has been utilised to visualise and measure droplets formed at different flowrates corresponding to constant superficial velocities. Comparing volumes of generated droplets in the two geometries of area ratio near 1.5, a significant increase in volume is reported for the larger aspect ratio utilised, at all superficial velocities tested. As both superficial velocity of continuous phase and flowrate ratio are fixed, superficial velocity of dispersed phase varies. However this variation is not considered to be large enough to justify the significant increase in the droplet volume. Therefore it can be concluded that droplet generation is influenced by the aspect ratio and thus the cross-section of the main channel and its effect should not be depreciated. The paper will present supporting evidence in detail and a comparison of the findings with the existing theories which are mainly focused on the squeezing regime.

scholarly journals Liquid–Liquid Flows with Non-Newtonian Dispersed Phase in a T-Junction Microchannel

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 335
Author(s):  
Anna Yagodnitsyna ◽  
Alexander Kovalev ◽  
Artur Bilsky
Keyword(s):  
Flow Pattern ◽  
Dynamic Viscosity ◽  
Slug Flow ◽  
Shear Thinning ◽  
Continuous Phase ◽  
Immiscible Liquid ◽  
Dispersed Phase ◽  
Effective Dynamic ◽  
Liquid Flows ◽  
Shear Thinning Fluid

Immiscible liquid–liquid flows in microchannels are used extensively in various chemical and biological lab-on-a-chip systems when it is very important to predict the expected flow pattern for a variety of fluids and channel geometries. Commonly, biological and other complex liquids express non-Newtonian properties in a dispersed phase. Features and behavior of such systems are not clear to date. In this paper, immiscible liquid–liquid flow in a T-shaped microchannel was studied by means of high-speed visualization, with an aim to reveal the shear-thinning effect on the flow patterns and slug-flow features. Three shear-thinning and three Newtonian fluids were used as dispersed phases, while Newtonian castor oil was a continuous phase. For the first time, the influence of the non-Newtonian dispersed phase on the transition from segmented to continuous flow is shown and quantitatively described. Flow-pattern maps were constructed using nondimensional complex We0.4·Oh0.6 depicting similarity in the continuous-to-segmented flow transition line. Using available experimental data, the proposed nondimensional complex is shown to be effectively applied for flow-pattern map construction when the continuous phase exhibits non-Newtonian properties as well. The models to evaluate an effective dynamic viscosity of a shear-thinning fluid are discussed. The most appropriate model of average-shear-rate estimation based on bulk velocity was chosen and applied to evaluate an effective dynamic viscosity of a shear-thinning fluid. For a slug flow, it was found that in the case of shear-thinning dispersed phase at low flow rates of both phases, a jetting regime of slug formation was established, leading to a dramatic increase in slug length.

Experimental Study on Flow Patterns of Decaying Swirling Gas-Liquid Flow in a Horizontal Pipe

2020 ◽  
Author(s):  
Shuai Liu ◽  
Li Liu ◽  
Jiarong Zhang ◽  
Hanyang Gu
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Separation Efficiency ◽  
Swirling Flow ◽  
Flow Patterns ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Gas Removal ◽  
Swirl Vane ◽  
Gas Liquid Flow

Abstract Swirling flow is one of the well-recognized techniques to control the working process. This special flow is widely adopted in swirl vane separators in nuclear steam generator (SG) for water droplet separation and the fission gas removal system in Thorium Molten Salt Reactor (TMSR) for gas bubble separation. Since the parameters such as separation efficiency, pressure drop and mass and heat transfer rate are strongly dependent on the flow pattern, the accurate prediction of flow patterns and their transitions is extremely important for the proper design, operation and optimization of swirling two-phase flow systems. In this paper, using air and water as working fluids, a visualization experiment is carried out to study the gas-liquid flow in a horizontal pipe containing a swirler with four helical vanes. The test pipe is 5 m in length and 30 mm in diameter. Firstly, five typical flow patterns of swirling gas-liquid flow at the outlet of the swirler are classified and defined, these being spiral chain, swirling gas column, swirling intermittent, swirling annular and swirling ribbon flow. Being affected by the different gas and liquid flow rate of non-swirling flow, it is found that the same non-swirling flow can change into different swirling flow patterns. After that, the evolution of various swirling flow patterns along the streamwise direction is analyzed considering the influence of swirl attenuation. The results indicate that the same swirling flow pattern can transform into a variety of swirling flow patterns and subsequent non-swirling flow patterns. Finally, the flow pattern maps at different positions downstream of the swirler are presented.

Two-Phase Flow Regime Transitions in Microchannel Tubes: The Effect of Hydraulic Diameter

2000 ◽  
Author(s):  
John W. Coleman ◽  
Srinivas Garimella
Keyword(s):  
Flow Regime ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Small Diameter ◽  
Flow Patterns ◽  
Hydraulic Diameter ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Mechanisms

Abstract An experimental investigation of two-phase flow mechanisms during condensation of refrigerant R134a in small diameter round and rectangular tubes was conducted. A 4.91 mm round tube, and four round tubes with hydraulic diameters ranging from 1 mm – 4 mm were studied to characterize the influence of tube miniaturization on the flow mechanisms. For each tube under consideration, flow mechanisms were recorded over the entire range of qualities 0 < x < 1, and for five different mass fluxes between 150 kg/m2-s and 750 kg/m2-s. Approximately 50 data points were recorded for each tube to obtain a comprehensive understanding of the effects of geometry, mass flux and quality on the phase-change flow mechanisms. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. In addition, the large amount of data over a wide range of test conditions enabled the delineation of several different flow patterns within each flow regime, which provides a clearer understanding of the different modes of two-phase flow. Transition lines between the respective flow patterns and regimes on these maps were established based on the experimental data. It was found that the intermittent flow regime becomes larger as the tube hydraulic diameter is decreased. Also, the size of the wavy flow regime decreases for the small diameter tubes, and disappears completely for the 1 × 1 mm square tube. These maps and transition lines can be used to predict the flow pattern or regime that will be established for a given mass flux, quality and tube geometry.

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