Film Fraction and Droplet Size inside of a Rectangular Venturi Scrubber

The Venturi scrubber, equipment frequently used in the removal of particles from gases, is constituted basically by a duct with a convergent section followed by a constriction, or throat, and a divergent section. A liquid, usually injected in the throat, is atomized by the flowing air at high speed. The formed droplets act as collectors of particles from the gas. The process of droplet formation from an injected liquid can be described as follows: the liquid enters the gas stream in the form of a jet, perpendicular to the gas flow. As the jet penetrates the gas stream, it is bent by the gas drag. After a given penetration distance, a burst occurs, and the remaining jet is disintegrated as a droplet cloud. Depending on the liquid and gas flow rates, the penetration on the jet into the gas stream may reach the walls of the equipment, and a fraction of liquid deposits in the form of a film. This film contributes little for the removal of particles from the dust laden gas. Few studies have analyzed the formation of film at the scrubber walls and its influence in the droplet size inside the Venturi scrubber. For this reason, the present study is focused on the experimental measurement of the deposition of the liquid film on the walls of a rectangular Venturi scrubber and, simultaneously, the estimation of the droplet size measured in the Venturi throat. The experiments were carried out varying the liquid flow rate, the gas velocity and the number of orifices of liquid injection. A correlation, using a dimensionless number, was proposed to quantify the influence of each experimental condition. The results indicate that film fraction has a significant influence in the droplet size measured inside of Venturi scrubber.

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Droplet Interaction in the Liquid Injection by Multiple Orifices in the Performance of a Venturi Scrubber

Materials Science Forum ◽

10.4028/www.scientific.net/msf.591-593.896 ◽

2008 ◽

Vol 591-593 ◽

pp. 896-901 ◽

Cited By ~ 1

Author(s):

Vádila Giovana Guerra ◽

M.A.F. Daher ◽

M.V. Rodrigues ◽

José Antônio Silveira Gonçalves ◽

José Renato Coury

Keyword(s):

Size Distribution ◽

High Speed ◽

Liquid Flow Rate ◽

Experimental Tests ◽

Liquid Jet ◽

Gas Velocity ◽

Venturi Scrubber ◽

Liquid Injection ◽

Multiple Jets ◽

Jet Penetration

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Analyzing Droplet Size Distributions Inside a Self-Priming Venturi Scrubber for Filtered Containment Venting Systems

Volume 6B: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-82227 ◽

2018 ◽

Author(s):

P. Papadopoulos ◽

T. Lind ◽

H.-M. Prasser

Keyword(s):

Droplet Size ◽

High Speed ◽

Nuclear Power ◽

Power Plants ◽

Gas Flow ◽

Tube Bundle ◽

Droplet Size Distribution ◽

Severe Accident ◽

Design Element ◽

Venturi Scrubber

After the accident in the Fukushima Daiichi nuclear power plant, the interest of adding Filtered Containment Venting Systems (FCVS) on existing nuclear power plants to prevent radioactive releases to the environment during a severe accident has increased. Wet scrubbers are one possible design element which can be part of an FCVS system. The efficiency of this scrubber type is thereby depending, among others, on the thermal-hydraulic characteristics inside the scrubber. The flow structure is mainly established by the design of the gas inlet nozzle. The venturi geometry is one of the nozzle types that can be found in nowadays FCVS. It acts in two different steps on the removal process of the contaminants in the gas stream. Downstream the suction opening in the throat of the venturi, droplets are formed by atomization of the liquid film. The droplets are contributing to the capture of aerosols and volatile gases from the mixture coming from the containment. Studies state that the majority of the contaminants is scrubbed within this misty flow regime. At the top of the venturi, the gas stream is injected into the pool. The pressure drop at the nozzle exit leads to the formation of smaller bubbles, thus increasing the interfacial area concentration in the pool. In this work, the flow inside a full-scale venturi scrubber has been optically analyzed using shadowgraphy with a high-speed camera. The venturi nozzle was installed in the TRISTAN facility at PSI which was originally designed to investigate the flow dynamics of a tube rupture inside a full-length scale steam generator tube bundle. The data analysis was focused on evaluating the droplet size distribution and the Sauter mean diameter under different gas flow rates and operation modes. The scrubber was operated in two different ways, submerged and unsubmerged. The aim was to include the effect on the droplet sizes of using the nozzle in a submerged operation mode.

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Droplet–turbulence interaction in a confined polydispersed spray: effect of droplet size and flow length scales on spatial droplet–gas velocity correlations

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.676 ◽

2014 ◽

Vol 741 ◽

pp. 98-138 ◽

Cited By ~ 16

Author(s):

S. Sahu ◽

Y. Hardalupas ◽

A. M. K. P. Taylor

Keyword(s):

Droplet Size ◽

Gas Flow ◽

Dynamic Range ◽

Energy Content ◽

Effective Length ◽

Flow Structures ◽

Stream Velocity ◽

Gas Velocity ◽

Length Scales ◽

Velocity Fluctuations

AbstractThis paper discusses the interaction between droplets and entrained turbulent air flow in the far-downstream locations of a confined polydispersed isothermal spray. Simultaneous and planar measurements of droplet and gas velocities in the spray along with droplet size are obtained with the application of a novel experimental technique, developed by Hardalupaset al. (Exp. Fluids, vol. 49, 2010, pp. 417–434), which combines interferometric laser imaging for droplet sizing (ILIDS) with particle image velocimetry (PIV). These measurements quantified the spatial correlation coefficients of droplet–gas velocity fluctuations ($R_{dg}$) and droplet–droplet velocity fluctuations ($R_{dd}$) conditional on droplet size classes, for various separation distances, and for axial and cross-stream velocity components. At the measurement location close to the spray edge, with increasing droplet size,$R_{dg}$was found to increase in axial direction and decrease in cross-stream direction. This suggests that as the gas-phase turbulence becomes more anisotropic away from the spray axis, the gravitational influence on droplet–gas correlated motion tends to increase. The effective length scales of the correlated droplet–gas motion were evaluated and compared with that for gas and droplet motion. The role of different turbulent eddies of the gas flow on the droplet–gas interaction was examined. The flow structures were extracted using proper orthogonal decomposition (POD) of the instantaneous gas velocity data, and their contribution on the spatial droplet–gas velocity correlation was evaluated, which quantified the momentum transfer between the two phases at different length scales of the gas flow. The droplets were observed to augment turbulence for the first three POD modes (larger scales) and attenuate it for the rest of the modes (smaller scales). It has been realized that apart from droplet Stokes number and mass loading, the dynamic range of length scales of the gas flow and the relative turbulent kinetic energy content of the flow structures (POD modes) must be considered in order to conclude if the droplets enhance or reduce the carrier-phase turbulence especially at the lower wavenumbers.

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Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging

International Journal of Chemical Reactor Engineering ◽

10.1515/1542-6580.2543 ◽

2011 ◽

Vol 9 (1) ◽

Author(s):

Ahmed Hassan Elshazly

Keyword(s):

Flow Rate ◽

Gas Flow ◽

Dye Removal ◽

Gas Velocity ◽

Gas Flow Rate ◽

Flow Rates ◽

Gas Sparging ◽

Current Densities ◽

Superficial Gas Velocity ◽

Time Of Operation

The present work investigates the effect of gas sparging in improving the performance of a batch electrocoagulation unit used to treat wastewater generated from the dyeing industry. Monopolar cylindrical aluminum electrodes were used. Many variables were investigated such as superficial gas velocity, current density, initial dye concentration, area ratio (cathode/anode), time of operation and the effect of adding chemical coagulant as FeSO4. The results show that the percentage of dye removal has been increased by a factor ranging from 2.52 to 5.14 by increasing the gas flow rate from 0.4 to 0.8 liter/min respectively and that about 93.5 percent of the dye can be removed within 60 minutes. Also it was found that using gas sparging is more efficient than adding chemical coagulant as ferrous sulfate for the removal of dye from wastewater. The power consumption for the unit was measured for different gas flow rates and different current densities; the results show that lower gas flow rate can improve the economy of the process.

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Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

Metals ◽

10.3390/met10050667 ◽

2020 ◽

Vol 10 (5) ◽

pp. 667 ◽

Cited By ~ 1

Author(s):

Elise Ferreira ◽

Morgan Dal ◽

Christophe Colin ◽

Guillaume Marion ◽

Cyril Gorny ◽

...

Keyword(s):

Gas Flow ◽

Industrial Applications ◽

Powder Flow ◽

Laser Metal Deposition ◽

Gas Velocity ◽

Flow Rates ◽

Manufacturing Method ◽

Precise Knowledge ◽

Particle Stream ◽

Weighting Methods

The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder streams characteristics is essential to control the process and improve its reliability and reproducibly for industrial applications. This paper proposes multiple experimental techniques, such as gas pressure measurement, optical and weighting methods, to analyze the gas and particle velocity, the powder stream diameter, its focal plan position and density. This was carried out for three nozzle designs and multiple gas and powder flow rates conditions. The results reveal that (1) the particle stream follows a Gaussian distribution while the gas velocity field is closer to a top hat one; (2) axial, carrier and shaping gas flow significantly impact the powder stream’s focal plan position; (3) only shaping gas, powder flow rates and nozzle design impact the powder stream diameter. 2D axisymmetric models of the gas and powder streams with RANS turbulent model are then performed on each of the three nozzles and highlight good agreements with experimental results but an over-estimation of the gas velocity by pressure measurements.

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Hydrodynamic Study of Bubbles in a Bubble Column Reactor Part II – Numerical Study

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.813-814.1023 ◽

2015 ◽

Vol 813-814 ◽

pp. 1023-1027

Author(s):

S. Arunkumar ◽

V. Harshavardhan Reddy ◽

T.M. Sreevathsav ◽

M. Venkatesan

Keyword(s):

High Speed ◽

Gas Flow ◽

Bubble Column ◽

Numerical Study ◽

Image Processing Technique ◽

Bubble Velocity ◽

Bubble Column Reactor ◽

Hydrodynamic Characteristics ◽

Flow Rates ◽

Column Reactor

The present work deals with the use of CFD analysis and the validation of the experimental work carried out on the artificial splitting of an air bubble in a bubble column reactor. In Part I of this work, artificial splitting of bubble in a bubble column rector is experimentally studied by using a high speed camera. Image processing technique was used to identify bubble size and bubble velocity. In present work CFD simulations are carried out using ANSYS FLUENT software using Volume of Fluids (VOF) method. VOF is based on a surface tracking technique applied to a fixed Eulerian space. The phase fraction in physical quantities that can be used to distinguish the distribution of gas hold up in a bubble Column reactor. The numerical study of splitting of bubble into two bubbles of nearly equal size is considered. In the bubble column reactor, the liquid phase is stationary and gas flow rate in it is varied. The superficial gas flow rates are 10 lph, 15 lph, 20 lph and 25 lph. The characteristics of bubble after splitting which include its shape, size and velocity for various gas flow rates mentioned above are studied numerically and are compared with experimental results. These hydrodynamic characteristics play a pivotal role in the reactions occurring between the liquid and gas phases in the bubble column reactor.

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Experimental Characterisation of the Interfacial Structure during Counter-Current Flow Limitation in a Model of the Hot Leg of a PWR

Science and Technology of Nuclear Installations ◽

10.1155/2012/298452 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Christophe Vallée ◽

Toshifumi Nariai ◽

Takashi Futatsugi ◽

Akio Tomiyama ◽

Dirk Lucas ◽

...

Keyword(s):

Water Level ◽

High Speed ◽

Gas Flow ◽

Current Flow ◽

Interfacial Structure ◽

Flow Limitation ◽

Two Phase ◽

Flow Rates ◽

Counter Current Flow ◽

Counter Current

In order to investigate the two-phase flow behaviour during counter-current flow limitation in the hot leg of a pressurised water reactor, dedicated experiments were performed in a scaled down model ofKobe University. The experiments were performed with air and water at atmospheric pressure and room temperature. At high flow rates, CCFL occurs and the discharge of water to the reactor pressure vessel simulator is limited by the formation of slugs carrying liquid back to the steam generator. The structure of the interface was observed from the side of the channel test section using a high-speed video camera. An algorithm was developed to recognise the stratified interface in the camera frames after background subtraction. This method allows extracting the water level at any position in the image as well as performing further statistical treatments. The evolution of the interfacial structure along the horizontal part of the hot leg is shown by the visualisation of the probability distribution of the water level and analysed in function of the liquid and gas flow rates. The data achieved are useful for the analysis of the flow conditions as well as for the validation of modelling approaches like computational fluid dynamics.

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Pulsatile Primary Slurry Atomization: Effects of Viscosity, Circumferential Domain, and Annular Slurry Thickness

Volume 6A: Energy ◽

10.1115/imece2015-53026 ◽

2015 ◽

Cited By ~ 2

Author(s):

Wayne Strasser ◽

Francine Battaglia

Keyword(s):

Droplet Size ◽

High Speed ◽

Gas Flow ◽

Computational Models ◽

Experimental Studies ◽

Sheet Thickness ◽

Liquid Sheet ◽

Inertial Subrange ◽

Computational Domain ◽

Turbulence Scale

A central theme of our prior experimental and computational work on a transonic self-sustaining pulsatile three-stream coaxial airblast injector involved obtaining spectral content from compressible 2-D models and preliminary droplet size distributions from incompressible 3-D models. The three streams entail an inner low-speed gas, and outer high-speed gas, and an annular liquid sheet. Local Mach numbers in the pre-filming region exceed unity due to gas flow blockage by the liquid. Liquid bridging at somewhat regular intervals creates resonance in the feed streams. The effects of numerical decisions and geometry permutations were elucidated. The focus now shifts to compressible 3-D computational models so that geometric parameters, modeled domain size, and non-Newtonian slurry viscosity can be more elaborately explored. While companion studies considered circumferential angles less than 45°, specific attention in this work is given to the circumferential angles larger than 45°, the slurry annular dimension, and how this annular dimension interacts with inner nozzle retraction (pre-filming distance). Additional metrics, including velocity point spectral analyses, are investigated. Two-stream experimental studies are also computationally studied. Multiple conclusions were drawn. Narrower annular slurry passageways yielded a thinner slurry sheet and increased injector throughput, but the resulting droplets were actually larger. Unfortunately the effect of slurry sheet thickness could not be decoupled from another important geometric permutation; injector geometry physical constraints mandated that, in order to thin the slurry sheet, the thickness of the lip which separates the inner gas and slurry had to be increased accordingly. Increased lip thickness reduced the interfacial shear and increased the thickness of the gas boundary layer immediately adjacent to the slurry sheet. This suppressed the sheet instability and reduced the resulting liquid breakup. Lastly, velocity point correlations revealed that an inertial subrange was difficult to find in any of the model permutations and that droplet length scales correlate with radial velocities. As anticipated, a higher viscosity resulted in larger droplets. Both the incremental impact of viscosity and the computed slurry length scale matched open literature values. Additionally, the employment of a full 360° computational domain produced a qualitatively different spray pattern. Partial azimuthal models exhibited a neatly circumferentially repeating outer sheath of pulsing spray ligaments, while full domain models showed a highly randomized and broken outer band of ligaments. The resulting quantitate results were similar especially farther from the injector; therefore, wedge models can be used for screening exercises. Lastly, droplet size and turbulence scale predictions for two external literature cases are presented.

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A laboratory study of recovery boiler smelt shattering

TAPPI Journal ◽

10.32964/tj13.8.19 ◽

2014 ◽

Vol 13 (8) ◽

pp. 19-26 ◽

Cited By ~ 1

Author(s):

ANTON TARANENKO ◽

MARKUS BUSSMANN ◽

HONGHI TRAN

Keyword(s):

Droplet Size ◽

Flow Rate ◽

Liquid Flow ◽

High Speed ◽

Liquid Flow Rate ◽

Liquid Viscosity ◽

Experimental Apparatus ◽

Nozzle Position ◽

Jet Velocity ◽

Recovery Boiler

A scaled-down experimental apparatus was built to examine smelt shattering during typical recovery boiler operations. Water-glycerine solutions and air were used in place of smelt and steam. A high-speed camera and image processing software were used to record and quantify liquid shattering in terms of droplet number and size distributions, as a function of air velocity, air nozzle position, liquid flow rate, and liquid viscosity. The results showed that increasing shatter jet velocity reduced average droplet size, increasing the liquid flow rate increased droplet size, and placing the shatter jet nozzle closer to the liquid stream decreased droplet size. These results were all as expected. The effect of liquid viscosity (1-50 cP) depended on the shatter jet velocity. At high air velocities, even the viscous liquid was well shattered, but at lower velocities, the effect of viscosity on shattering was significant.

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Increasing the Productivity of Gas Wells in Conditions of High Water Factors

10.2118/208564-ms ◽

2021 ◽

Author(s):

Serhii Matkivskyi ◽

Liliia Khaidarova

Keyword(s):

Flow Rate ◽

Liquid Flow ◽

Gas Flow ◽

Liquid Flow Rate ◽

High Water ◽

Gas Flow Rate ◽

Flow Rates ◽

Production Wells ◽

Water Cut ◽

Gas Lift

The overwhelming majority of natural gas fields are at the final stage of development, which, along with other features, is characterized by selective watering of productive deposits and production wells. The difficulty of extracting residual gas reserves under such development conditions is associated with depletion of productive reservoirs, accumulation of fluid at the bottom of wells, corrosion of downhole equipment and the inability to reduce wellhead pressures due to restrictions on the supply and preparation of hydrocarbon products with the existing surface infrastructure. Production wells in conditions of formation water inflow into productive deposits are decommissioned after relatively small gas withdrawals. This is due both to the insufficient implementation of methods for intensifying the removal of fluid from the bottom of the wells, and to the peculiarities of the arrangement of fields, which are usually not designed for the collection and preparation of hydrocarbon products with a high liquid content. In order to remove the gas-liquid mixture from the bottom of the wells, many techniques and inventions have been developed that are widely used in production. The developed technologies are characterized by different efficiency and have a number of technological limitations, mainly due to the peculiarities of the geological structure of hydrocarbon deposits. Considering the above, there is a need for additional research in order to improve the existing and develop new technologies for the operation of water cut wells. Using the special software package, studies were carried out to optimize the operating conditions for a water cut well under conditions of active formation water inflow into gas-saturated horizons. The study was carried out for various depths of gas-lift valves (3500 m; 3000 m; 2500 m; 2000 m; 1500 m; 1000 m) and liquid flow rates (22.5 m3/day; 33.75 m3/day and 45 m3/day). Based on the research results, graphical dependences of gas flow rates and bottomhole pressure on the amount of gas-lift gas were built; the maximum gas flow rate and the required amount of gas-lift gas from the liquid flow rate; maximum gas flow rate versus liquid flow rate at different depths of gas-lift valve installation. Based on the results of statistical processing of the calculated data for each value of the liquid flow rate, the optimal value of the depth of the gas-lift valve was established. According to the results of the studies performed, to ensure the stable operation of high-water cut gas wells, it is effective to locate the gas-lift valve at a distance of 55-58 % from the wellhead of the tubing (2033-2137 m).

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