Showing papers on "Slug flow published in 2014"
TL;DR: In this article, an optically transparent polymer electrolyte membrane (PEM) water electrolysis cell was studied using a high-speed camera, thermal imaging and electrochemical impedance spectroscopy to examine the relationship between flow and electrical performance.
121 citations
TL;DR: In this paper, a unit cell model is proposed to study the absorption of CO2 bubbles under slug flow in a T-junction microchannel, and the amount of gas absorbed during the bubble formation process has been measured to be about 2-10% of the inlet gas phase.
106 citations
TL;DR: The slug-flow crystallizer as mentioned in this paper is a continuous crystallizer with the potential to provide improved control of crystal properties, improved process reproducibility, and reduced scale-up risk.
Abstract: A novel continuous crystallizer design is described with the potential to provide improved control of crystal properties, improved process reproducibility, and reduced scale-up risk. Liquid and gas are introduced into one end of the tube at flow rates selected to spontaneously generate alternating slugs of liquid and gas that remain stable while cooling crystallization occurs in each liquid slug. Mixing within each stable self-circulating slug is maximized by controlling the slug aspect ratio through specification of liquid and gas flow rates. The crystallizer is designed so that nucleation and growth processes are decoupled to enhance the individual control of each phenomenon. Coaxial or radial mixers combine liquid streams to generate seed crystals immediately upstream of the growth zone where nucleation is minimized, and crystal growth is controlled by the varying temperature profile along the length of the tube. The slug-flow crystallizer design is experimentally demonstrated to generate large uniform...
99 citations
TL;DR: In this paper, a liquid-liquid mass transfer mechanism with slug flow in microreactor is investigated by means of experiments in square microchannels of 0.2 and 0.3 mm width.
94 citations
TL;DR: In this article, the air-water two-phase flow in a tapered channel of a PEMFC was numerically simulated using the volume of fluid (VOF) method.
75 citations
TL;DR: In this article, the performance of a gas-liquid cylindrical cyclone (GLCC) separator was investigated under various inflow operating conditions, and the effect of the inlet nozzle design on the performances of the separator is studied by using three different nozzles.
74 citations
TL;DR: In this article, an algebraic interfacial area density (AIAD) approach was used to predict key flow features like liquid hold-up and free surface waviness, and an evaluation of the velocity and turbulence fields predicted by the AIAD model against experimental data was done.
68 citations
TL;DR: In this article, the effects of friction and restitution coefficients of particles on horizontal pneumatic conveying by a combined approach of computational fluid dynamics for gas and discrete element method for particles are analyzed in terms of particle flow pattern, gas pressure drop, solid concentration, particle velocity and transition of flow regime.
63 citations
TL;DR: A three-phase slug flow and a parallel-slug flow are reported as two major flow patterns found under the nitrogen-decane-water flow through a glass microfluidic chip which features a long microchannel with a hydraulic diameter of 98 μm connected to a cross-flow mixer.
Abstract: We report a three-phase slug flow and a parallel-slug flow as two major flow patterns found under the nitrogen–decane–water flow through a glass microfluidic chip which features a long microchannel with a hydraulic diameter of 98 μm connected to a cross-flow mixer. The three-phase slug flow pattern is characterized by a flow of decane droplets containing single elongated nitrogen bubbles, which are separated by water slugs. This flow pattern was observed at a superficial velocity of decane (in the range of about 0.6 to 10 mm s−1) typically lower than that of water for a given superficial gas velocity in the range of 30 to 91 mm s−1. The parallel-slug flow pattern is characterized by a continuous water flow in one part of the channel cross section and a parallel flow of decane with dispersed nitrogen bubbles in the adjacent part of the channel cross section, which was observed at a superficial velocity of decane (in the range of about 2.5 to 40 mm s−1) typically higher than that of water for each given superficial gas velocity. The three-phase slug flow can be seen as a superimposition of both decane–water and nitrogen–decane slug flows observed in the chip when the flow of the third phase (viz. nitrogen or water, respectively) was set at zero. The parallel-slug flow can be seen as a superimposition of the decane–water parallel flow and the nitrogen–decane slug flow observed in the chip under the corresponding two-phase flow conditions. In case of small capillary numbers (Ca ≪ 0.1) and Weber numbers (We ≪ 1), the developed two-phase pressure drop model under a slug flow has been extended to obtain a three-phase slug flow model in which the ‘nitrogen-in-decane’ droplet is assumed as a pseudo-homogeneous droplet with an effective viscosity. The parallel flow and slug flow pressure drop models have been combined to obtain a parallel-slug flow model. The obtained models describe the experimental pressure drop with standard deviations of 8% and 12% for the three-phase slug flow and parallel-slug flow, respectively. An example is given to illustrate the model uses in designing bifurcated microchannels that split the three-phase slug flow for high-throughput processing.
63 citations
TL;DR: In this paper, the authors investigated the characteristics of gas-liquid two-phase flow under elevated pressure up to 3.0 MPa in a microchannel and showed that a strong leakage flow through the channel corners occurs although the gas bubbles block the channel.
Abstract: Characteristics of gas-liquid two-phase flow under elevated pressures up to 3.0 MPa in a microchannel are investigated to provide the guidance for microreactor designs relevant to industrial application. The results indicate that a strong leakage flow through the channel corners occurs although the gas bubbles block the channel. With a simplified estimation, the leakage flow is shown to increase with an increase in pressure, leading to a bubble formation shifting from transition regime to squeezing regime. During the formation process, the two-phase dynamic interaction at the Tjunction entrance would have a significant influence on the flow in the main channel as the moving velocity of generated bubbles varies periodically with the formation cycle. Other characteristics such as bubble formation frequency, bubble and slug lengths, bubble velocities, gas hold-up, and the specific surface area are also discussed under different system pressures. V C 2013 American Institute of Chemical Engineers AIChE J, 60: 1132–1142, 2014
54 citations
TL;DR: Erosion measurements in multiphase slug and annular flow regimes have been made in a horizontal 762 mm (3-in) diameter pipe as discussed by the authors, where experiments were performed with superficial gas velocities ranging from 152 m/s (50 ft/s) to 457 m/S (150 ft/S) and superficial liquid velocity ranging from 046 m/z (15 ft/m) to 076 m/n/s, for liquid viscosities of 1 cP and 10 cP Three different sand sizes (20, 150, and
Abstract: Erosion measurements in multiphase slug and annular flow regimes have been made in a horizontal 762 mm (3-in) diameter pipe These flow regimes are selected since they produce higher metal losses than other flow regimes, and they also occur for a wide variety of operating conditions Experiments are performed with superficial gas velocities ranging from 152 m/s (50 ft/s) to 457 m/s (150 ft/s) and superficial liquid velocities ranging from 046 m/s (15 ft/s) to 076 m/s (25 ft/s), for liquid viscosities of 1 cP and 10 cP Three different sand sizes (20, 150, and 300 μm sand) were used for performing tests The shapes of the sand are also different with the 20 and 300 μm sand being sharper than the 150 μm sand Erosion measurements are obtained using electrical resistance (ER) probes which relate the change in electrical resistance to the change in the thickness of an exposed element resulting from erosion Two probes are placed in a bend and another probe is placed in a straight section of pipe The probes in the bend are flat-head probes, and they are placed flush with the outer wall in the 45 deg and 90 deg positions The probe in the straight pipe is an angle-head probe which protrudes into the flow with the face placed in the center of the pipe
TL;DR: The experimental results show that the neural network method is able to learn the implicit correlations between the characteristic parameters of slug flow and the corresponding gas and liquid flow rates.
Abstract: This paper presents a method to obtain gas and liquid flow rates of two-phase air-water slug flow in a horizontal pipe through conductance probes and neural network. Contrary to statistical features commonly used in other works, five characteristic parameters of the mechanistic slug flow model are extracted from conductance signals, i.e., translational velocity, slug holdup, film holdup, slug length, and film length, which are used as the neural network inputs. The translational velocity is obtained through cross correlation of signals from the two ring-type conductance probes that are placed apart at a fixed distance. A feedforward neural network is adopted to correlate the characteristic parameters of slug flow and the gas and liquid flow rates and further used as a prediction tool. The experimental results show that the neural network method is able to learn the implicit correlations between the characteristic parameters of slug flow and the corresponding gas and liquid flow rates. It provides a performance for measurement of gas and liquid flow rates in slug flow regime within ±10% of full scale.
TL;DR: In this article, an investigation of the hydrodynamics of slug flow in a vertical 67 mm internal diameter riser was performed using a multiphase air-silicone oil mixture over a range of gas (0.42
TL;DR: In this article, a wire mesh sensor based on conductance measurements was applied to investigate two-phase horizontal pipe flow in a 76 mm ID pipe, 18 m long, to generate stratified and annular flow conditions.
Abstract: Stratified and annular gas-liquid flow patterns are commonly encountered in oil and gas transportation pipelines. The measurement and visualization of two-phase flow characteristics is of great importance as two-phase flows persist in many fluids engineering applications. A Wire Mesh Sensor technique based on conductance measurements was applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate stratified and annular flow conditions. A 16×16 wire configuration sensor, installed at 17 m from the inlet test section, is used to determine the void fraction within the cross-section of the pipe. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing techniques. In this work, the principle of wire mesh sensors and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, mean void fraction and characteristic liquid film velocities are determined for different liquid and gas superficial velocities that ranged from 0.03 m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters are also investigated using three different viscosities.Copyright © 2013 by ASME
TL;DR: In this article, the behavior of two-phase air-water mixture flowing from the horizontal to the vertical through a 90° bend has been investigated experimentally using conductance probe technique.
TL;DR: In this article, the impact of two-phase flow maldistribution on PEM fuel cell performance was investigated using a volume of fluid (VOF) model coupled with a 1D MEA model.
TL;DR: In this article, the hydrodynamics of single-phase liquid flow with relatively high fluid viscosities in a microchannel was investigated experimentally and a modified capillary number representing the mutual effects of the viscosity of the continuous phase and the dispersed phase was proposed for predicting the slug sizes in microchannels.
Abstract: The hydrodynamics of single-phase liquid flow with relatively high fluid viscosities in a microchannel was investigated experimentally. The results showed that the conventional theory could predict the single-phase flow with high fluid viscosities in microchannels. Furthermore, the effect of viscosity on the slug flow of two immiscible liquid phases in a microchannel was studied with high-speed imaging techniques. It was found that a higher dispersed-phase viscosity quickened the flow pattern transition from slug flow to parallel flow and resulted in smaller slugs. A modified capillary number representing the mutual effects of the viscosities of the continuous phase and the dispersed phase was proposed for predicting the slug sizes in microchannels.
TL;DR: In this article, the effects of different two-phase flow patterns on the permeate flux were studied in a microfiltration process, and different trends were observed in the dimensionless groups' plane (N s, Nf) indicating different effects of gas-liquid twophase flow on the resistances and fouling.
TL;DR: In this paper, the authors applied a high speed video camera system to study the characteristics of slug flow in a vertical narrow rectangular channel (3.25×-43mm) and compared the results with the existing literature.
TL;DR: Antony et al. as discussed by the authors reviewed various liquid-liquid flow regimes in a micro-channel and discussed on the hydrodynamics of flow in micro-scale systems, focusing especially on the mass trans-fer between two liquid phases in slug flow and details of experimental studies carried out in this area.
Abstract: Mass transfer is a basic phenomenon behind many processes like reaction, absorption, extraction etc. Mass transfer plays a significant role in microfluidic systems where the chemical / biological process systems are shrinkened down to a micro scale. Micro reactor system, with its high compatibility and performance, gains a wide interest among the researchers in the recent years. Micro structured reac-tors holds advantages over the conventional types in chemical processes. The significance of micro re-actor not limited to its scalability but to energy efficiency, on-site / on-demand production, reliability, safety, highly controlled outputs, etc. Liquid-liquid two phase reaction in a microreactor system is highly demandable when both reactants are liquids or when air medium cannot be suitable. This arti-cle overviews various liquid-liquid flow regimes in a microchannel. Discussions on the hydrodynamics of flow in micro scale are made. Considering the importance of mass transfer in liquid-liquid systems and the advantage of slug regime over other regimes, the article focuses especially on the mass trans-fer between two liquid phases in slug flow and the details of experimental studies carried out in this area. The advantages of slug flow over other flow regimes in micro structured reactor applications are showcased. © 2014 BCREC UNDIP. All rights reserved Received: 31st May 2014; Revised: 6th August 2014; Accepted: 14th August 2014 How to Cite : Antony, R., Giri Nandagopal, M.S., Sreekumar, N., Rangabhashiyam, S., Selvaraju, N. (2014). Liquid-liquid Slug Flow in a Microchannel Reactor and its Mass Transfer Properties - A Review. Bulletin of Chemical Reaction Engineering & Catalysis ,9(3): 207-223. (doi:10.9767/bcrec.9.3.6977.207-223) Permalink/DOI : http://dx.doi.org/10.9767/bcrec.9.3.6977.207-223
TL;DR: In this article, the Piston Flow Model (PFM) is proposed to predict the time dependent forces acting on horizontal pipe bends in slug flow, and the PFM has been validated by comparing its predictions with their experimental results for air-water slug flow.
Abstract: In this paper, a one-dimensional, transient theoretical model, the Piston Flow Model (PFM), based on momentum analysis, is proposed to predict the time dependent forces acting on horizontal pipe bends in slug flow. Our experimental apparatus is described and results there from are presented. The PFM has been validated by comparing its predictions with our experimental results for air–water slug flow. The pressure traces, force traces and maximum force predicted agree well with our measurements.
TL;DR: In this paper, a large number of experiments were carried out in a 25-m long near-horizontal pipeline with an internal diameter of 100mm, and detailed measurements of the flow were made with the X-ray system at various superficial velocities, two different pressures (4 and 7.2 bara, giving gas densities of 24 and 42 kg/m3, respectively), and three different inclination angles: 0, +1 and +5 degrees.
TL;DR: In this paper, the authors investigated experimentally the flow of high viscosity-oil and gas in a horizontal and inclined pipe providing new data sets on high-viscosity oil multiphase pipe flows that include experimental pressure drops, bubble frequencies and lengths, holdups measured using capacitance probes.
TL;DR: In this paper, a general framework for the simulation of turbulent, compressible, multi-phase, multimaterial flows is described based on interface-capturing and a compositional approach in which each component represents a different phase/fluid.
TL;DR: In this paper, phase transition processes of RP-3 kerosene flowing inside a square quartz-glass tube were experimentally investigated, and three distinct phase transition phenomena (liquid-gas two phase flow under sub-critical pressures, critical opalescence under critical pressure, and corrugation under supercritical pressures) were identified.
TL;DR: In this article, the effect of liquid viscosity on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X-ray tomography.
Abstract: A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µL ≤ 1149 mPa-s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X-ray tomography. The internal dynamic flow structure and the bubble size distribution shows a dual role of the liquid viscosity on the hydrodynamics. Further, the effect of solid concentration (Cs = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo slurry viscosities similar to the liquid viscosities of the gas–liquid systems. The effects of liquid and pseudo slurry viscosities on flow structure, bubble size distribution, and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition from homogeneous bubbly to slug flow regime occurs is initiated by the addition of particles as compared to the particle free system for apparently same viscosity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3079–3090, 2014
TL;DR: In this paper, moving slugs of plastic pellets were investigated in-situ during low velocity pneumatic conveying in horizontal pipelines and a strong correlation between particle velocity and wall stresses was found, suggesting that the stresses responsible for the high pressure loss characterising slug flow may result mostly from the transfer of particle impulses to the pipe wall.
TL;DR: In this paper, the effects of hose diameter and flow velocity on the characteristics of high-lift siphon drains were investigated and the experimental results show that the flow characteristics of siphon drainage are significantly influenced by the hose diameter.
Abstract: This paper presents a study of flow characteristics in high-lift siphon drains A laboratory test was conducted to investigate the effects of hose diameter and flow velocity on siphon drainage Three types of water flow were observed and analyzed The experimental results show that the flow characteristics of siphon drainage are significantly influenced by the hose diameter Water flows in the form of a wall pressing flow in a large diameter siphon hose (eg, larger than 50 mm) under low flow velocity, which leads to discontinuous siphon drainage However, water flows in the form of an integral slug flow in a small diameter siphon hose (eg, smaller than 40 mm) under low flow velocity, which leads to continuous siphon drainage Based on experimental observations, a thermodynamic derivation of the threshold of siphon hose diameter for continuous siphon drainage was analytically conducted In slope engineering, a 36 mm polyurethane (PU) hose is recommended for siphon drainage
TL;DR: In this paper, the effect of surfactant on vertical gas-liquid two-phase flow was experimentally simulated in a low pressure apparatus, and the results showed that the maximum liquid holdup reduction induced by the surfactants was high up to 88.6% which appeared in churn flow.
TL;DR: In this paper, the effects of void fraction correlations on pressure gradient separation of air-water two-phase flow in vertical rectangular ducts were investigated experimentally under ambient temperature and pressure, and the results indicated that although the void fraction correlation has great influence on gravitational pressure gradient of slug flow, churn flow and annular flow, it nearly has no influence on that of bubbly flow.