A Droplet Generator with Electronic Control of Size, Production Rate, and Charge

Abbott, Charles E.; Cannon, Theodore W.

doi:10.1063/1.1685913

Cited by 27 publications

(5 citation statements)

References 4 publications

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“…The large drops were generated using a technique involving hypodermic needles and a constant water pressure head. The smaller water drops were formed using a drop generator of the type developed by Abbot and Cannon (1972). In the experiments with smaller drops, between 100 and 200 individual drops were collected for analysis.…”

Section: Designmentioning

confidence: 99%

On the scavenging of SO2 by cloud and raindrops: II. An experimental study of SO2 absorption and desorption for water drops in air

et al. 1983

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For the purpose of testing our previously described theory of SO z scavenging a laboratory investigation was carried out in the UCLA 33 m long rainshaft. Drops with radii between 250 and 2500 ~tm were allowed to come to terminal velocity, after which they passed through a chamber of variable length filled with various SO 2 concentrations in air. After falling through a gas separating chamber consisting of a fluorocarbon gas the drops were collected and analyzed for their total S content in order to determine the rate of SO 2 absorption.The SO: concentration in ak studied ranged between 1 and 60% (v). Such relatively large concentrations were necessary due to the short times the drops were exposed to SO s in the present setup. The present experimental results were therefore not used to simulate atmospheric conditions but rather to test our previously derived theory which is applicable to any laboratory or atmospheric condition. Comparison of our studies with the results from our theory applied to our laboratory conditions led to predicted values for the S concentration in the drops which agreed well with those observed if the drops had radii smaller than 500 ~m. In order to obtain agreement between predicted and observed S concentrations in larger drops, an empirically derived eddy diffusivity for SO 2 in water had to be included in the theory to take into account the effect of turbulent mixing inside such large drops.In a subsequent set of experiments, drops initially saturated with S (IV) were allowed to fall through S-free air to determine the rate of SO s desorption. The results of these studies also agreed well with the results of our theoretical model, thus justifying the reversibility assumption made in our theoretical models. In a final set of experiments, the effects of oxidation on SO s absorption was studied by means of drops containing various amounts of H20 ~. For comparable exposure times to SO 2, the S concentration in drops with H:O 2 was found to be up to 10 times higher than the concentration in drops in which no oxidation occurred.

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Section: Designmentioning

confidence: 99%

On the scavenging of SO2 by cloud and raindrops: II. An experimental study of SO2 absorption and desorption for water drops in air

et al. 1983

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“…Noticeable contamination only occurred for times longer than about three minutes, approximately twice as long as that needed to complete a run. While large drops were prepared using a hypodermic syringe fed from a constant head water supply, small drops were produced by an Abbot and Cannon (1972) drop generator. Large drops were sized by collecting a known number and weighing them on a Mettler balance.…”

Section: Methodsmentioning

confidence: 99%

Absorption and desorption of dichloromethane vapor by water drops in air. An experimental test of scavenging theory

et al. 1989

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An experimental study of the scavenging ofdichloromethane vapor by water drops falling at terminal velocity, has been carried out in the UCLA precipitation shaft, in order to test the predictions of theoretical washout models. Whereas good agreement between theory and experiment was found for drops of radius 0.332 mm, computed gas uptake rates for 1.253 and 2.21 mm radius drops were much slower than those measured, just as reported previously for the washout of both sulfur dioxide and acetaldehyde. An analysis shows that theory can be reconciled with all of the experimental data by replacing the compound specific aqueous phase Fickian molecular diffusion coefficient used in the theory, by an 'effective diffusivity', having a constant value, (3 × 10 -4 cm 2 s -1), independent of the physical and chemical nature of the absorbed species, for all drops of equivalent radii greater than 0.9 mm.

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“…Water droplets in the size range 50-200/•m with a controllable charge (0 to -I-50 fC) were produced at the rate of about 1 Hz by an Abbott and Cannon [1972] droplet generator on top of the cold room. Each droplet then froze slowly as it fell down a tube into the cold room and collided with a tenuous cloud of minute ice crystals that was formed by cooling a short section of the tube.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Ice conductivity restraints on the inductive theory of thunderstorm electrification

Illingworth¹,

Caranti²

1985

J. Geophys. Res.

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According to the inductive theory of thunderstorm electrification, a small ice crystal bouncing off the underside of a larger hydrometeor falling in the presence of an electric field should remove some of the field‐induced polarization charge from the surface of the larger particle; subsequent gravitational separation of the two particles should then result in a rapid growth of the electric field. However, because of the finite surface conductivity of the ice, it is not obvious that the polarization charges can flow along the ice surface in the short interaction time. We report laboratory experiments on the effect of an external electric field on the charge transferred during individual collisions of small (typically, 100‐μm) ice spheres with larger ice targets. When the surface conductivity of the ice was artificially increased by using 10−2 M NaCl, the full theoretical charge transfer was observed, but at 10−5 M NaCl, no field‐dependent charge transfer could be detected. Airborne measurements of cloud and precipitation purity have shown that 10−4 M NaCl is occasionally reached in low‐level stratiform clouds in polluted regions, but even with this degee of contamination the inductive mechanism operates at less than 20% of its potential efficiency at −10°C; at lower temperatures this fraction is reduced still further. We conclude that the inductive mechanism cannot account for the observed electrification of thunderstorms unless other contaminants are having an unexpectedly large effect on the conductivity.

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A Droplet Generator with Electronic Control of Size, Production Rate, and Charge

Cited by 27 publications

References 4 publications

On the scavenging of SO2 by cloud and raindrops: II. An experimental study of SO2 absorption and desorption for water drops in air

On the scavenging of SO2 by cloud and raindrops: II. An experimental study of SO2 absorption and desorption for water drops in air

Absorption and desorption of dichloromethane vapor by water drops in air. An experimental test of scavenging theory

Ice conductivity restraints on the inductive theory of thunderstorm electrification

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