Size-resolved particle deposition velocities of sub-100nm diameter particles over a forest

Vertical laminar flow (VLF) cleanrooms generally operate with airflows between 60 feet per minute (fpm) and 110 fpm. Tests were performed to evaluate the effects on particle contamination levels when the airflow velocity in a FED-STD-209 Class 1 VLF cleanroom was reduced. The cleanroom normally operates at 90 fpm. Measurements of surface particle concentrations were made on settling monitor wafers and on wafers carried in an open cassette. Optical particle counters measured the airborne particle concentrations at several locations. Results at 100 fpm and 50 fpm, respectively, for particles larger than or equal to 0.3 μm in optical equivalent diameter were −0.0002 and +0.0029 particles/sq cm/hr for the settling wafers and 0.009 and 0.024/sq cm total for the wafers carried for 5 hr in the open cassettes. Summary statistics are provided for the airborne and surface particle counts. Deposition velocity is the ratio of surface deposition rate to airborne concentration. For the monitor wafers at the lower flow, the calculated particle deposition velocities were near 0.003 cm/sec, which is within the range expected from theory and experiments in the literature.

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Micrometeorological measurements of particle deposition velocities to moorland vegetation

Quarterly Journal of the Royal Meteorological Society ◽

10.1256/qj.01.71 ◽

2002 ◽

Vol 128 (585) ◽

pp. 2281-2300 ◽

Cited By ~ 59

Author(s):

Eiko Nemitz ◽

Martin W. Gallagher ◽

Jan H. Duyzer ◽

David Fowler

Keyword(s):

Particle Deposition ◽

Micrometeorological Measurements ◽

Deposition Velocities

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Improved Discrete Random Walk Stochastic Model for Simulating Particle Dispersion and Deposition in Inhomogeneous Turbulent Flows

Journal of Fluids Engineering ◽

10.1115/1.4047538 ◽

2020 ◽

Vol 142 (10) ◽

Author(s):

Amir A. Mofakham ◽

Goodarz Ahmadi

Keyword(s):

Random Walk ◽

Turbulent Flows ◽

Particle Deposition ◽

Finite Size ◽

Particle Dispersion ◽

Concentration Profiles ◽

Velocity Fluctuations ◽

Point Particles ◽

Deposition Velocities ◽

Gradient Drift

Abstract The performance of different versions of the discrete random walk models in turbulent flows with nonuniform normal root-mean-square (RMS) velocity fluctuations and turbulence time scales were carefully investigated. The OpenFOAM v2−f low Reynolds number turbulence model was used for evaluating the fully developed streamwise velocity and the wall-normal RMS velocity fluctuations profiles in a turbulent channel flow. The results were then used in an in-house matlab particle tracking code, including the drag and Brownian forces, and the trajectories of randomly injected point-particles with diameters ranging from 10 nm to 30 μm were evaluated under the one-way coupling assumption. The distributions and deposition velocities of fluid-tracer and finite-size particles were evaluated using the conventional-discrete random walk (DRW) model, the modified-DRW model including the velocity gradient drift correction, and the new improved-DRW model including the velocity and time gradient drift terms. It was shown that the conventional-DRW model leads to superfluous migration of fluid-point particles toward the wall and erroneous particle deposition rate. The concentration profiles of tracer particles obtained by using the modified-DRW model still are not uniform. However, it was shown that the new improved-DRW model with the velocity and time scale drift corrections leads to uniform distributions for fluid-point particles and reasonable concentration profiles for finite-size heavy particles. In addition, good agreement was found between the estimated deposition velocities of different size particles by the new improved-DRW model with the available data.

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Evaluation of five dry particle deposition parameterizations for incorporation into atmospheric transport models

10.5194/gmd-2017-93 ◽

2017 ◽

Cited By ~ 1

Author(s):

Tanvir R. Khan ◽

Judith A. Perlinger

Keyword(s):

Monte Carlo ◽

Particle Deposition ◽

Atmospheric Transport ◽

Current Knowledge ◽

Input Parameter ◽

Coniferous Forest ◽

Three Dimensions ◽

Transport Models ◽

Deposition Velocities ◽

Parameter Values

Abstract. Despite considerable effort to develop mechanistic dry particle deposition parameterizations for atmospheric transport models, current knowledge has been inadequate to propose quantitative measures of the relative performance of available parameterizations. In this study, we evaluated the performance of five dry particle deposition parameterizations developed by Zhang et al. (2001) (Z01), Petroff and Zhang (2010) (PZ10), Kouznetsov and Sofiev (2012) (KS12), Zhang and He (2014) (ZH14), and Zhang and Sao (2014) (ZS14), respectively. The evaluation was performed in three dimensions: model ability to reproduce observed deposition velocities, Vd (accuracy), the influence of imprecision in input parameter values on the modeled Vd (uncertainty), and identification of the most influential parameter(s) (sensitivity). The accuracy of the modeled Vd was evaluated using observations obtained from five land use categories (LUCs): grass, coniferous and deciduous forests, natural water, and ice/snow. To ascertain the uncertainty in modeled Vd, and quantify the influence of imprecision in key model input parameters, a Monte Carlo uncertainty analysis was performed. The Sobol' sensitivity analysis was conducted with the objective to determine the parameter ranking, from the most to the least influential. Comparing the normalized mean bias factors (indicator of accuracy), we find that the ZH14 parameterization is the most accurate for all LUCs except for coniferous forest, for which it is second most accurate (BNMBF = −2.31). From Monte Carlo simulations, the estimated mean normalized uncertainties in the modeled Vd obtained for seven particle sizes (ranging from 0.005 to 2.5 μm) for the five LUCs are 17 %, 12 %, 13 %, 16 %, and 27 % for the Z01, PZ10, KS12, ZH14, and ZS14 parameterizations, respectively. From the Sobol' sensitivity results, we suggest that the parameter rankings vary by particle size and LUC for a given parameterization. Overall, for dp = 0.001 to 1.0 μm, friction velocity was one of the three most influential parameters in all parameterizations. For giant particles (dp = 10 μm), relative humidity was the most influential parameter. Because it is the least complex of the five parameterizations, and it has the greatest accuracy and least uncertainty, we propose that the ZH14 parameterization is currently superior for incorporation into atmospheric transport models.

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Deposition of Submicron Aerosol Particles During Integrated Circuit Manufacturing: Experiments

Journal of the IEST ◽

10.17764/jiet.1.32.1.m52036842044n049 ◽

1989 ◽

Vol 32 (1) ◽

pp. 27-45

Author(s):

Jin Wu ◽

Robert Miller ◽

Douglas Cooper ◽

James Flynn ◽

Douglas Delson ◽

...

Keyword(s):

Integrated Circuit ◽

Particle Deposition ◽

Measurement Data ◽

Condensation Nucleus ◽

Submicron Particles ◽

Integrated Circuit Manufacturing ◽

Deposition Velocities ◽

Optical Particle Counter ◽

Theoretical Predictions ◽

Made In

Measurements of airborne concentrations and surface concentrations of submicron particles were made in two different semiconductor manufacturing cleanrooms. These measurements, made with an optical particle counter, a condensation nucleus counter, and a surface contamination optical monitor were used to determine the particle fluxes and the particle deposition velocities. The measurement data were compared with theoretical predictions of deposition due to gravity, diffusion, and electrostatic effects.

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Numerical Simulation of Deposition of Calcium Carbonate Particles Suspended in the Turbulent Cooling Water Flow

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-38864 ◽

2010 ◽

Author(s):

M. Izadi ◽

D. K. Aidun ◽

P. Marzocca ◽

L. Tian

Keyword(s):

Calcium Carbonate ◽

Water Flow ◽

Particle Deposition ◽

Deposition Velocity ◽

Cooling Water ◽

Nano Particles ◽

Mean Flow ◽

Ansys Fluent ◽

Micro Particles ◽

Deposition Velocities

Calcium carbonate is predominantly present in cooling tower’s water and is usually the principal cause of hard water. This paper applies the modeling technique typically used for aerosol deposition to simulate the deposition process of calcium carbonate nano- and micro-particles suspended in turbulent cooling water flows. The mean turbulent velocity field and the fluctuating velocities are determined by the k-ε and RSM turbulence models by simulating the water flow in a typical heat exchanger horizontal tube. Commercial software (ANSYS FLUENT™ 12.1.4) is used for turbulence mean flow modeling and the simulation of turbulence fluctuations is performed by stochastic models. Particle deposition velocities are obtained for the particles with diameters in the range 0.01–50 μm by the k-ε and RSM models and compared to the deposition velocities calculated from semi-empirical correlations to investigate the effect of the turbulence model on the deposition velocity. Results show that the proposed numerical model can predict deposition velocity of micro-particles in water accurately and can be useful in determining the range of particle diameters in which the highest deposition velocity occurs. However, for nano-particles, the model’s results do not agree with the correlations due to the higher lateral turbulence fluctuations calculated by ANSYS FLUENT™ code. The proposed model can be useful for predicting fouling in industrial heat exchangers, for planning operations and cleaning schedules, and proposing efficient filtering processes for lowering deposition rate and cleaning costs.

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A Laser Doppler Method for the determination of particle deposition velocities

Journal of Aerosol Science ◽

10.1016/0021-8502(89)90013-x ◽

1989 ◽

Vol 20 (3) ◽

pp. 381-390 ◽

Cited By ~ 2

Author(s):

W. Holländer ◽

G. Pohlmann ◽

G. Morawietz

Keyword(s):

Particle Deposition ◽

Laser Doppler ◽

Doppler Method ◽

Deposition Velocities

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A comparison of dry and wet season aerosol number fluxes over the Amazon rain forest

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-26881-2009 ◽

2009 ◽

Vol 9 (6) ◽

pp. 26881-26924

Author(s):

L. Ahlm ◽

E. D. Nilsson ◽

R. Krejci ◽

E. M. M&aring;rtensson ◽

M. Vogt ◽

...

Keyword(s):

Dry Deposition ◽

Rain Forest ◽

Particle Deposition ◽

Particle Flux ◽

Friction Velocity ◽

Deposition Velocity ◽

Dry Season ◽

Wet Season ◽

Deposition Velocities ◽

Amazon Rain Forest

Abstract. Vertical number fluxes of aerosol particles and vertical fluxes of CO2 were measured with the eddy covariance method at the top of a 53 m high tower in the Amazon rain forest as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment. The observed aerosol number fluxes included particles with sizes down to 10 nm in diameter. The measurements were carried out during the wet and dry season in 2008. In this study focus is on the dry season aerosol fluxes, with significant influence from biomass burning, and these are compared with aerosol fluxes measured during the wet season. The primary goal is to quantify the dry deposition sink and to investigate whether particle deposition velocities change when going from the clean wet season into the more polluted dry season. Furthermore, it is tested whether the rain forest is always a net sink of particles in terms of number concentrations, or if particle emission from the surface under certain circumstances may dominate over the dry deposition sink. The particle deposition velocity vd increased linearly with increasing friction velocity in both seasons and the relations are described by vdd=(2.7 u* −0.2)×10−3 (dry season) and vdw=2.5 u*×10−3 (wet season), where u* is the friction velocity. The fact that the two relations are very similar to each other indicates that the seasonal change in aerosol number size distribution is not enough for causing any significant change in deposition velocity. In general, particle deposition velocities in this study are low compared to studies over boreal forests. The reason is probably domination of accumulation mode particles in the Amazon boundary layer, both in the dry and wet season, and low wind speeds in the tropics compared to the midlatitudes. Net particle deposition fluxes prevailed in daytime in both seasons and the deposition flux was considerably larger in the dry season due to the much higher dry season particle concentration. In the dry season, nocturnal particle fluxes behaved very similar to the nocturnal CO2 fluxes. Throughout the night, the measured particle flux at the top of the tower was close to zero, but early in the morning there was an upward particle flux peak that is not likely a result of entrainment or local pollution. It is possible that these morning upward particle fluxes are associated with emission of natural biogenic particles from the rain forest. Emitted particles may be stored within the canopy during stable conditions at nighttime, similarly to CO2, and being released from the canopy when conditions become more turbulent in the morning.

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Evaluation of five dry particle deposition parameterizations for incorporation into atmospheric transport models

Geoscientific Model Development ◽

10.5194/gmd-10-3861-2017 ◽

2017 ◽

Vol 10 (10) ◽

pp. 3861-3888 ◽

Cited By ~ 14

Author(s):

Tanvir R. Khan ◽

Judith A. Perlinger

Keyword(s):

Monte Carlo ◽

Particle Deposition ◽

Atmospheric Transport ◽

Current Knowledge ◽

Input Parameter ◽

Coniferous Forest ◽

Three Dimensions ◽

Transport Models ◽

Deposition Velocities ◽

Parameter Values

Abstract. Despite considerable effort to develop mechanistic dry particle deposition parameterizations for atmospheric transport models, current knowledge has been inadequate to propose quantitative measures of the relative performance of available parameterizations. In this study, we evaluated the performance of five dry particle deposition parameterizations developed by Zhang et al. (2001) (Z01), Petroff and Zhang (2010) (PZ10), Kouznetsov and Sofiev (2012) (KS12), Zhang and He (2014) (ZH14), and Zhang and Shao (2014) (ZS14), respectively. The evaluation was performed in three dimensions: model ability to reproduce observed deposition velocities, Vd (accuracy); the influence of imprecision in input parameter values on the modeled Vd (uncertainty); and identification of the most influential parameter(s) (sensitivity). The accuracy of the modeled Vd was evaluated using observations obtained from five land use categories (LUCs): grass, coniferous and deciduous forests, natural water, and ice/snow. To ascertain the uncertainty in modeled Vd, and quantify the influence of imprecision in key model input parameters, a Monte Carlo uncertainty analysis was performed. The Sobol' sensitivity analysis was conducted with the objective to determine the parameter ranking from the most to the least influential. Comparing the normalized mean bias factors (indicators of accuracy), we find that the ZH14 parameterization is the most accurate for all LUCs except for coniferous forest, for which it is second most accurate. From Monte Carlo simulations, the estimated mean normalized uncertainties in the modeled Vd obtained for seven particle sizes (ranging from 0.005 to 2.5 µm) for the five LUCs are 17, 12, 13, 16, and 27 % for the Z01, PZ10, KS12, ZH14, and ZS14 parameterizations, respectively. From the Sobol' sensitivity results, we suggest that the parameter rankings vary by particle size and LUC for a given parameterization. Overall, for dp  =  0.001 to 1.0 µm, friction velocity was one of the three most influential parameters in all parameterizations. For giant particles (dp  =  10 µm), relative humidity was the most influential parameter. Because it is the least complex of the five parameterizations, and it has the greatest accuracy and least uncertainty, we propose that the ZH14 parameterization is currently superior for incorporation into atmospheric transport models.

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