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flow patterns and pressure drop of ionic liquid-water two-phase flows in microchannels

INTERNATIONAL JOURNAL OF MULTIPHASE flow 2013年 54卷 1-10页

作者： Tsaoulidis, Dimitrios Dore, Valentina Angeli, Panagiota Plechkova, Natalia V. Seddon, Kenneth R. UCL Dept Chem Engn London WC1E 7JE England Queens Univ Belfast Sch Chem & Chem Engn QUILL Res Ctr Belfast BT9 5AG Antrim North Ireland

The two-phase flow of a hydrophobic ionic liquid and water was studied in capillaries made of three different materials (two types of Teflon, FEP and Tefzel, and glass) with sizes between 200 pm and 270 gm. The ionic liquid was 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, with density and viscosity of 1420 kg m(-3) and 0.041 kg m(-1) s(-1), respectively. flow patterns and pressure drop were measured for two inlet configurations (T- and Y-junction), for total flow rates of 0.065-214.9 cm(3) h(-1) and ionic liquid volume fractions from 0.05 to 0.8. The continuous phase in the glass capillary depended on the fluid that initially filled the channel. When water was introduced first, it became the continuous phase with the ionic liquid forming plugs or a mixture of plugs and drops within it. In the Teflon microchannels, the order that fluids were introduced did not affect the results and the ionic liquid was always the continuous phase. The main patterns observed were annular, plug, and drop flow. Pressure drop in the Teflon microchannels at a constant ionic liquid flow rate, was found to increase as the ionic liquid volume fraction decreased, and was always higher than the single phase ionic liquid value at the same flow rate as in the two-phase mixture. However, in the glass microchannel during plug flow with water as the continuous phase, pressure drop for a constant ionic liquid flow rate was always lower than the single phase ionic liquid value. A modified plug flow pressure drop model using a correlation for film thickness derived for the current fluids pair showed very good agreement with the experimental data. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Micro-fluidics Liquid-liquid Pressure drop flow patterns Ionic liquids

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flow patterns in a four-branch junction with supercritical flow

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JOURNAL OF HYDRAULIC ENGINEERING 2008年第6期134卷 701-713页

作者： Mignot, Emmanuel Riviere, Nicolas Perkins, Richard Paquier, Andre Irstea Hydrol Hydraul Res Unit F-69336 Lyon 09 France Univ Lyon CNRS ECL INSAL UCBL1 INSA Lyon Lab Mecan Fluides & Acoust F-69621 Villeurbanne France Univ Lyon CNRS ECL INSAL UCBL1 INSA Lyon Lab Mecan Fluides & Acoust F-69134 Ecully France

This paper describes the flow structures that occur in a 90 degrees junction of four open channels with supercritical flow in two orthogonal inlet channels. An experimental facility was constructed to permit the measurement of flow rates, water depths, and the positions of hydraulic jumps in the channels. The various flow patterns which appear depend on the characteristics of the incoming flows and can be classified into three main types, depending on the location and shape of the hydraulic jumps that develop. These jumps can either be normal to the flow and located in the upstream channels, or can be oblique and confined within the junction. The explanation for the existence of various flow patterns is derived from previous studies of the rapid deflection of supercritical flow. A detailed description of each flow regime is provided, with information on the surface elevations, the behavior of the hydraulic jumps, the deflections of the incoming flows, and the formation and characteristics of recirculation zones.

关键词： Channels Deflection flow patterns flow rates Hydraulic jump Supercritical flow

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flow patterns of (3+1)-dimensional solutions of the Charney-Obukhov equation

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NONLINEAR DYNAMICS 2024年第14期112卷 12361-12374页

作者： Myagkov, N. N. Kudryavtsev, A. G. Russian Acad Sci Inst Appl Mech Moscow 125040 Russia

We consider flow patterns for exact solutions of the (3 + 1)-dimensional nonlinear nondissipative quasi-geostrophic potential vorticity equation, also known as the Charney-Obukhov equation, for Rossby vortices in the ocean propagating along the zonal direction with a constant velocity V. The following results are obtained: (a) For a given value of V the vortices are localized in the vicinity of one or several planes z=zci,i=1,2,...L\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z = z_{ci} ,_{{}} i = 1,_{{}} 2,_{{}} ..._{{}} L$$\end{document}, where 0 <= zci <= H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0 \le z_{ci} \le H$$\end{document} and L is the number of such planes, which are determined by the zonal flow included in the exact solution of the Charney-Obukhov equation;(b) Heton-like model of a baroclinic dipole, whose vortices are localized in two horizontal XY-planes, located one above the other. The heton can propagate both to the west and to the east with a velocity significantly exceeding the Rossby wave speed, this heton model is realized both in cylindrically symmetric solutions and in spherically symmetric solutions;(c) We consider a non-central "collision" of vortex monopoles and dipoles localized in the horizontal XY-plane, depending on their polarization and orientation in space. The "collision" of vortices is described as a sequence of stationary states, each of which is an exact solution to the Charney-Obukhov equation. The result of a non-central "collision": two unipolar vortices merge, two oppositely polarized vortices form a dipole, two oppositely directed dipoles form a tripole upo

关键词： Charney-Obukhov equation Ocean flow patterns Hetons Collision of vortices, Collision of dipolar vortices

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flow patterns IN RADIAL flow HOLLOW FIBER REVERSE-OSMOSIS SYSTEMS

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DESALINATION 1988年第1期68卷 11-28页

作者： GILL, WN MATSUMOTO, MR GILL, AL LEE, YT SUNY BUFFALO DEPT CHEM ENGNBUFFALONY 14260 SUNY BUFFALO DEPT CIVIL ENGNBUFFALONY 14260

In the past, mathematical models describing the separation characteristics of radial flow hollow fiber reverse osmossis units have used ideal plug-flow models. Recently, Soltanieh and Gill [1,2] have developed a model based on the assumption of complete mixing on the shell side of these modules. The purpose of this study is to determine by independent experiments which flow model best described these units, and describe radial flow packed bed systems in general. Experimentally obtained tracer-response curves are compared to theoretical response curves based on the plug-flow and complete-mixed models. A theoretical model which is based on Darcy's law for time variable flow, the complete-mix time variable (CMTV) flow model, was found to fit the experimental data well.

关键词： reverse osmosis hollow fibers flow patterns modeling

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flow patterns and sediment deposition in rectangular shallow reservoirs

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WATER AND ENVIRONMENT JOURNAL 2012年第4期26卷 504-510页

作者： Dufresne, Matthieu Dewals, Benjamin Erpicum, Sebastien Archambeau, Pierre Pirotton, Michel Univ Liege ULg Hydraul Environm & Civil Engn HECE ArGEnCo Dept Liege Belgium

This work involves the experimental investigation of flow patterns, preferential regions of deposition and trapping efficiency in rectangular shallow reservoirs. The main flow patterns that can be encountered in rectangular shallow reservoirs are described: symmetrical flows without any reattachment point (S0), asymmetrical flows with one reattachment point (A1) and asymmetrical flows with two reattachment points (A2). The influence of geometrical and hydraulic parameters on reattachment lengths is intensively investigated. A shape parameter is introduced to classify symmetrical and asymmetrical flows. For each flow pattern, the preferential regions of deposition are studied. To conclude, a number of practical recommendations are given. Reservoirs with a shape parameter lower than 6.2 limit sediment deposition. Reservoirs with a shape parameter greater than 6.8 are favourable for sediment deposition. Finally, perspectives for maximizing and minimizing deposition are given, respectively by exploiting the great trapping potential of the flow pattern A1 and the poor trapping potential of the flow pattern S0.

关键词： flow patterns rectangular shallow reservoirs sediment deposition

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flow patterns and bubble departure fundamental characteristics during flow boiling in microscale channels

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2014年 59卷 152-165页

作者： Tibirica, Cristiano Bigonha Ribatski, Gherhardt Univ Sao Paulo Escola Engn Sao Carlos Dept Mech Engn Sao Carlos SP Brazil

This paper presents an experimental investigation into the fundamental characteristics of flow boiling in microscale channels based on diabatic high-speed flow visualizations. Experiments were conducted with R134a and R245fa refrigerants flowing in a 0.40 mm circular horizontal channel for mass velocities ranging from 100 to 900 kg/m(2) s and heat fluxes of up to 226 kW/m(2). flow images were captured at recording speeds of up to 100,000 frames/s. Results for bubble departure diameter and frequency, bubble growth ratio, slug frequency and velocity, flow pattern transitions, characteristics of the liquid film and liquid vapor interface are provided. The experimental data obtained are carefully analyzed, discussed and compared against previous results for tubes of 1.00 and 2.00 mm internal diameter. Predictive methods available in the literature for bubble departure diameter and frequency are evaluated by comparing their predictions against the data obtained in the present study. New bubble departure diameter and frequency correlations are proposed for small channels. The following conclusions can be drawn from the present study: (i) bubbles can detach from the wall with diameters much smaller than the tube diameter;(ii) the bubble growth process has a square root time-dependence;(iii) two different methods for estimating the average surface heat flux based on flow boiling videos have been developed;(iv) bubble active nucleation sites are observed for all flow patterns;(v) buoyancy effects are still present for a 0.40 mm tube, and (vi) six different sources of vapor liquid interface oscillations have been identified. (C) 2014 Elsevier Inc. All rights reserved.

关键词： flow patterns Two-phase flow Bubble nucleation Bubble frequency Microchannels

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flow patterns and oil-water dispersion in a 0.38 m diameter oscillatory baffled column

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CANADIAN JOURNAL OF CHEMICAL ENGINEERING 2000年第1期78卷 211-220页

作者： Ni, XW Nelson, G Mustafa, I Heriot Watt Univ Dept Mech & Chem Engn Edinburgh EH14 4AS Midlothian Scotland Bonar Polymers Ltd Newton Aycliff D25 6YE Durham England

We report our experimental flow visualization observations of flow patterns and experimental oil-water dispersion measurements in an oscillatory baffled column (OBC) of an internal diameter 380 mm. Both types of experiments were carried out covering an identical range of oscillation frequencies, amplitudes, orifice diameters and baffle spacings. The flow visualization observations show that eddy mixing has been achieved in the pilot OBC and the intensity of which is largely dependent on the operational and geometrical parameters tested, which is similar to that in a smaller scale OBC. The scale-up correlation was found to be linear. The oil-water dispersion measurements show that the degree of the dispersion depends significantly on the oscillation frequency and amplitude with an increase in either leading to an increase in dispersion. The effect of the orifice diameter on the oil-water dispersion is also evident, but the effect of the baffle spacing is much weaker. Based on the experimental data we have established a correlation relating the degree of oil-water dispersion to the power input to the system. We have also compared the power requirement to achieve a complete dispersion in the pilot OBC with that in a bench scale OBC of 50 mm diameter and found that the energy dissipation is more economical in the large scale application.

关键词： oscillatory baffled column flow patterns oil-water dispersion power dissipation

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flow patterns and pressure drop in air/water two-phase flow in horizontal helicoidal pipes

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JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME 1995年第4期117卷 720-726页

作者： Awwad, A Xin, RC Dong, ZF Ebadian, MA Soliman, HM FLORIDA INT UNIV DEPT MECH ENGNMIAMIFL 33199 UNIV MANITOBA DEPT MECH ENGNWINNIPEGMB R3T 2N2CANADA

An experimental investigation is conducted for air/water two-phase flow in horizontal helicoidal pipes. The helicoidal pipes are constructed of 25.4 mm I.D. Tygon tubing wrapped around cylindrical concrete forms with outside diameters of 62 cm and 124 cm. The helix angles of the helicoidal pipes vary from 1 to 20 deg. The experiments are performed for superficial water velocity in a range of U-L = 0.008 similar to 2.2 m/s and for superficial air velocity in a range of U-G = 0.2 similar to 50 m/S. The flow patterns are discerned and recorded photographically. The pressure drop of the air/water two-phase flow in the coils is measured and the Lockhart-Martinelli approach is used to analyze the data. The results are presented in the form of frictional pressure drop multipliers versus the Lockhart-Martinelli parameter. It tvas found that the flow patterns differ greatly from those of the straight pipe, and that the frictional pressure drop multipliers depend on both the Lockhart-Martinelli parameter and the flow rates. The correlation of the frictional pressure drop has been provided based on the current data. Furthermore, it was also Sound that the helix angle of the helicoidal pipe had almost no effect on the air/water two-phase flow pressure drop in the present experimental ranges.

关键词： WINDING ANGLE Pressure decline Pipe Water velocity piping air velocity flow patterns Coils Skin friction TWO PHASE flow

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flow patterns and transport in Rayleigh surface acoustic wave streaming:: Combined finite element method and raytracing numerics versus experiments

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 2008年第10期55卷 2298-2305页

作者： Frommelt, Thomas Gogel, Daniel Kostur, Marcin Talkner, Peter Haenggi, Peter Wixforth, Achim Univ Augsburg Inst Phys D-8900 Augsburg Germany Silesian Univ Inst Phys PL-40007 Katowice Poland

This work presents an approach for determining the streaming patterns that are generated by Rayleigh surface acoustic waves in arbitrary 3-D, geometries by finite element method (FEM) simulations. An efficient raytracing algorithm is applied on the acoustic subproblem to avoid the unbearable memory demands and computational time of a conventional FEM acoustics simulation in 3-D. The acoustic streaming interaction is modeled by a body force term in the Stokes equation. In comparisons between experiments and simulated flow patterns, we demonstrate the quality of the proposed technique.

关键词： acoustic streaming finite element analysis microfluidics surface acoustic waves FEM acoustics simulation Rayleigh surface acoustic wave streaming Stokes equation acoustic subproblem arbitrary 3D geometries finite element method flow transport ray tracing Ray tracing Physical Strength (2004) Finite element method Rayleigh Surface acoustic waves Microfluidics acoustic streaming flow patterns Streaming

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flow patterns of pulverized coal pneumatic conveying and time-series analysis of pressure fluctuations

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CHEMICAL ENGINEERING SCIENCE 2013年 101卷 303-314页

作者： Cong, Xingliang Guo, Xiaolei Lu, Haifeng Gong, Xin Liu, Kai Sun, Xiaolei Xie, Kai E China Univ Sci & Technol Key Lab Coal Gasificat & Energy Chem Engn Minist Educ Shanghai Engn Res Ctr Coal Gasificat Shanghai 200237 Peoples R China

flow instability is a key question which needs to be solved for the development of dense-phase pneumatic conveying. flow patterns are closely related with flow instability. There is a gap in our knowledge of gas solid flow patterns in the dense-phase pneumatic conveying due to the lack of advanced measure technology and analysis methods. Electrical Capacitance Tomography (ECT) is an effective and advanced measure method which was used to research flow patterns in pulverized coal dense phase pneumatic conveying with solid gas ration of 60-560 kg/kg. With stack of ECT images in order of time, different How patterns were defined and classified in the horizontal and vertical pneumatic conveying systems. Plug flow, fluidized flow, slug flow and stratified flow were observed in the horizontal pneumatic conveying;there were plug flow, fluidized flow, slug flow and annular How in the vertical pneumatic conveying. The relationship between Reynolds number and Archimedes number was used to predict transition of these flow patterns. The prediction is in good agreement with experimental results in the experimental range. In addition, some analysis methods were introduced to research the flow patterns, such as the Standard Deviation (SD), Power Spectrum Density (PSD) and wavelet analysis. We found that flow stability can be represented with SD and PSD. PSD is preferred to SD for its higher resolution ratio and noise immunity. The wavelet analysis can reflect flow characteristics and energy distributions in the different scales for different flow patterns. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Transport processes Powders Multiphase flow Tomography Pressure fluctuations flow patterns

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