Droplet Transfer from Suspending Air to Duct Walls

Alexander, L.G.; Coldren, C. L.

doi:10.1021/ie50498a024

Cited by 47 publications

(13 citation statements)

References 6 publications

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“…All droplets in the cylinder projected upstream of the sampling probe should have -been collected because the droplets were large and moving rapidly. Similar techniques for measuring entrained liquid in two-phase flow were used by Alexander and Coldren (1951), Wicks and Dukler (1960), and Gill et al (1963); they found no significant change in measured liquid flux over a wide range of probe sampling velocities. (1) the throat inlet, (2) the axial midpoint of the throat, (3) the throat outlet, (4) the axial midpoint of the diverging section, and (5) ,the diverging section outlet.…”

Section: Methodsmentioning

confidence: 79%

“…This "net" droplet deposition can then be modeled as gas-phase limited mass transfer with mass transfer coefficient K,; that is, once a droplet reaches the gas-liquid interface near the wall, its inertia carries it to the wall and it cannot return to the gas stream (Alexander and Coldren, 1951;Namie and Ueda, 1973). T h s assumption is supported by radial liquid distributions observed by Leith et al (1985).…”

Section: Liquid Deposition To the Wallmentioning

confidence: 99%

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Gas-Borne Liquid Flow Rate in a Venturi Scrubber with Two Different Liquied Injection Arrangements

Koehler

Feldman

Leith

1987

Aerosol Science and Technology

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Although current theory for venturi scrubber efficiency assumes that gas-borne liquid flow rate, QL, remains constant throughout the scrubber, it actually varies as liquid evaporates, condenses, atomizes from the scrubber wall, or deposits to the wall. Experiments were conducted to measure QL at various locations in a venturi scrubber. Water was injected in two ways: (1) radially inward through a circumferential slot at the throat inlet, and (2) axially downward through a centered pipe at the converging section inlet. For each liquid injection arrangement, Q , was determined by measuring the water in the gas at 180 points in the venturi, under each of nine operating conditions defined by varying liquiddo-gas ratio and gas velocity in the throat. For radial injection, relatively little injected water was found to be gas borne throughou* the scrubber, whereas for axial injection, most or all injected water remained in the gas. For both liquid injection arrangements, the radial distribution of gas-borne liquid varied consistently with axial position; under every operating condition, the concentration of gas-borne liquid in the throat was highest near the injection point, whereas by the end of the diverging section, it was highest near the centerline. A mathematical model is proposed to explain the observed axial variations in gas-borne liquid Row rate. NOMENCLATUREA total cross-sectional area, m2A, cross-sectional area tor location j, m2 C average droplet mass concentration 111 gas core, kg/m3 Koehler, Feldman, and Leith fractional penetration (fraction of particles of specified diameter not collected by scrubber), dimensionless gas volumetric flow rate, m3/s gas volumetric flow rate entering scrubber (measured), m3/s gas-borne liquid volumetric flow rate, m3/s liquid volumetric flow rate injected into scrubber (measured), m3/s injected liquid-to-gas ratio (measured), dimensionless liquid volumetric flow rate injected into scrubber (model input; see Table I), m3/s liquid volumetric flow rate on wall, m3/s instantaneous change in Q , at specified axial position, m3/s local scrubber radius, m inlet and outlet duct radi-US, m throat radius, m cross-sectional radius, m gas-phase Reynolds number, dimensionless wall surface area, m2 sum of squares droplet velocity relative to scrubber wall, m/s gas velocity relative to scrubber wall, m/s gas velocity in throat relative to scrubber wall, m/s ratio of actual liquid flow rate at location j to average liquid flow rate through scrubber cross section, dimensionless

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Section: Methodsmentioning

confidence: 79%

Section: Liquid Deposition To the Wallmentioning

confidence: 99%

Gas-Borne Liquid Flow Rate in a Venturi Scrubber with Two Different Liquied Injection Arrangements

Koehler

Feldman

Leith

1987

Aerosol Science and Technology

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“…Studies of the dispersion of solid and liquid particles in turbulent gas streams have led to a better understanding of the contributing variables (5,28,133,138,222). A detailed analysis of statistical properties of momentum transfer in two-phase flow was presented by Soo (222) who based his analysis on the followi.ng assumptions:…”

Section: Andmentioning

confidence: 99%

“…Alexander et al (7) Several qualitative conclusions on the phenomenon of jet mixing in a duot oan be drawn from the data available in the literature (5,6,7,28,107,116,154,240).…”

Section: C) Extension For Special Casesmentioning

confidence: 99%

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Heat and mass transfer to decelerating finely atomized sprays

Manning

Gauvin

1960

AIChE Journal

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The transfer of heat, mass and momentum in the nozzle zone of sprays produced by internal-mixing, pneumatic and hollow-cone, pressure nozzles was determined for both co-current and cross-current drying air flow patterns. The Nusselt Numbers for the evaporating .drops were correlated by means of the equation proposed by Ranz and Marshall for stationary drops in a rnoving air flow. Values of the drag coefficients for the decelerating drops, over a range of Reynolds Numbers of 1 to lOO, were approximately one tenth of those predicted by the standard curve for spheres, and a dependance on the drop diameter was observed.Methods of measuring the physical properties of the water-air system were developed and tested with special attention devoted to the determination of drop velocities and air humidity.

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Film formation in two‐phase annular flow

Anderson

Russell

1970

AIChE Journal

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The liquid film in annular two-phase flow is maintoined by droplet movement to and from the gas core and by wave action. This work examines droplet movement and its effect on the liquid film. Film formation and movement both axially and circumferentially were investigated by using transient techniques.The simultaneous flow of a gas and a liquid in a closed conduit occurs frequently in engineering practice. If the conduit is a horizontal pipeline and the phases are flowing concurrently, there are seven visually classified flow patterns that can exist ( 2 ) , depending on the mass flow rates of each phase, the physical properties of each phase, and the pipeline geometry. For high mass flow rates of gas (for example, 10,000 lb./hr. x sq.ft. for air) and a ratio of the liquid mass flow rate to the gas mass flow rate of 100 or less ( 4 ) , the flow pattern that will exist is called annularIn fully developed annular flow, the gas flows as a high speed core down the center of the pipeline. The liquid flows in two ways: in an annular film around the pipe wall and as droplets entrained by the gas core. For a given liquid rate, the fraction of the liquid flowing as entrained droplets increases as the gas rate is increased. There is a dynamic equilibrium between the droplets in the gas core and the film. New droplets are continually being formed at the gas-liquid interface, and droplets in the core continually impinge on the film. This phenomenon is known as interchange.The effect of these entrained droplets on heat and mass transfer in annular flow is of obvious importance, since the droplets greatly increase the interfacial area between the two phases. Moreover, because of interchange, new droplets are continually being generated at the gas-liquid interface, while droplets which have been in the gas core return to the film. This convected transport will greatly affect the overall rates of mass, momentum, and heat transfer.In order to quantitatively predict the effect of interchange, it would be necessary to have the following information:1. The rate of droplet generation and its circumferential 2. Information on the movement of droplets while they 3. The rate of droplet deposition and its circumferential This paper presents experimental results from a 1 in. I.D. horizontal pipeline on the rate of droplet deposition and its circumferential variation. Two kinds of interchange from the gas core to the liquid film were measured. One is a value of interchange which is an average value for the entire pipe circumference. In fully developed annular flow, this will also be the circumferential averaged value of interchange from the film to the core because of the dynamic equilibrium which exists. In the paper, this kind of interchange is denoted by I and has units of pounds per second per foot of pipe. The second kind of interchange measured is a value for a specified circumferential position; it is denoted by G and has units of pounds per second per square foot of inside pipe surface. pow.variation.are in the gas core. variation. ...

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Droplet Transfer from Suspending Air to Duct Walls

Cited by 47 publications

References 6 publications

Gas-Borne Liquid Flow Rate in a Venturi Scrubber with Two Different Liquied Injection Arrangements

Gas-Borne Liquid Flow Rate in a Venturi Scrubber with Two Different Liquied Injection Arrangements

Heat and mass transfer to decelerating finely atomized sprays

Film formation in two‐phase annular flow

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