Transport of small particles to vertical surfaces

Wells, A. C.; Chamberlain, A. C.

doi:10.1088/0508-3443/18/12/317

Cited by 190 publications

(101 citation statements)

References 7 publications

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“…This leveling of dimensionless deposition velocities for large values of τ + has been corroborated experimentally by Forney & Spielman (1974). Wells & Chamberlain (1967) were the first to investigate deposition in the diffusion regime. Their data confirmed the expected decrease in deposition with increases in particle size within the diffusion regime until Brownian diffusion becomes negligible.…”

Section: 33a Particle Size and Air Velocitysupporting

confidence: 62%

“…Theoretical (Browne, 1974;Wood, 1981a;Fan & Ahmadi, 1993;Li et al, 1994) and experimental (El-Shobokshy, 1983;Wells & Chamberlain, 1967;Lai, 1997) evidence suggests that both roughness scales influence particle deposition. All real materials possess microscale roughness, and this has rarely been quantified in deposition experiments.…”

Section: Details About Experiments In Straight Tubes and Ductsmentioning

confidence: 99%

“…Abstract 1 Wells & Chamberlain (1967) for deposition to vertically oriented smooth brass and fibrous filter paper (with roughness length scale, k, of about 100 µm). 2.23 Description of parameters to determine the particle capture distance to a rough surface by the method recommended by Browne (1974).…”

Section: Table Of Contentsmentioning

confidence: 99%

“…When particle deposition is the concern, quantification of surface roughness is needed rather than simple classification of the surface as hydraulically smooth. Macroscale roughness, in the form of fibers or grasses (Chamberlain, 1967;Wells & Chamberlain, 1967;Sehmel, 1970a), repeated ribs (Chamberlain et al, 1984;Hahn et al, 1985;Lai, 1997) and uniform three-dimensional elements (Lai, 1997), has been more frequently characterized and its influence on deposition more systematically investigated. Roughnesses reported in Tables 2.2-2.5 include both microscale and macroscale conditions.…”

Section: Details About Experiments In Straight Tubes and Ductsmentioning

confidence: 99%

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Particle deposition in ventilation ducts

Sippola¹

2002

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Exposure to airborne particles is detrimental to human health and indoor exposures dominate total exposures for most people. The accidental or intentional release of aerosolized chemical and biological agents within or near a building can lead to exposures of building occupants to hazardous agents and costly building remediation.Particle deposition in heating, ventilation and air-conditioning (HVAC) systems may significantly influence exposures to particles indoors, diminish HVAC performance and lead to secondary pollutant release within buildings. This dissertation advances the understanding of particle behavior in HVAC systems and the fates of indoor particles by means of experiments and modeling.Laboratory experiments were conducted to quantify particle deposition rates in horizontal ventilation ducts using real HVAC materials. Particle deposition experiments were conducted in steel and internally insulated ducts at air speeds typically found in ventilation ducts, 2-9 m/s. Behaviors of monodisperse particles with diameters in the size range 1-16 µm were investigated. Deposition rates were measured in straight ducts with 1 2 a fully developed turbulent flow profile, straight ducts with a developing turbulent flow profile, in duct bends and at S-connector pieces located at duct junctions. In straight ducts with fully developed turbulence, experiments showed deposition rates to be highest at duct floors, intermediate at duct walls, and lowest at duct ceilings. Deposition rates to a given surface increased with an increase in particle size or air speed. Deposition was much higher in internally insulated ducts than in uninsulated steel ducts. In most cases, deposition in straight ducts with developing turbulence, in duct bends and at S-connectors at duct junctions was higher than in straight ducts with fully developed turbulence.Measured deposition rates were generally higher than predicted by published models.A model incorporating empirical equations based on the experimental measurements was applied to evaluate particle losses in supply and return duct runs. Model results suggest that duct losses are negligible for particle sizes less than 1 µm and complete for particle sizes greater than 50 µm. Deposition to insulated ducts, horizontal duct floors and bends are predicted to control losses in duct systems. When combined with models for HVAC filtration and deposition to indoor surfaces to predict the ultimate fates of particles within buildings, these results suggest that ventilation ducts play only a small role in determining indoor particle concentrations, especially when HVAC filtration is present.However, the measured and modeled particle deposition rates are expected to be important for ventilation system contamination. ChairDate

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Section: 33a Particle Size and Air Velocitysupporting

confidence: 62%

Section: Details About Experiments In Straight Tubes and Ductsmentioning

confidence: 99%

Section: Table Of Contentsmentioning

confidence: 99%

Section: Details About Experiments In Straight Tubes and Ductsmentioning

confidence: 99%

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Particle deposition in ventilation ducts

Sippola¹

2002

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“…Particle throughput in a flow tube due to diffusion to the walls is taken into account by the penetration term, P = n out /n in , which is defined as the ratio of the particle concentration coming out of the cylindrical tube at a distance L (n out ) to that at distance L = 0 (n in ). Calculations of P for this system for either laminar (Hinds 1999) or turbulent flow regimes (Friedlander and Johnstone 1957;Wells and Chamberlain 1967;Lee and Gieseke 1994) show that even for the smallest particles sampled by SMPS (21 nm), particle loss by diffusion to the walls is ≤2% and represents a negligible loss for particles larger than 50 nm. Additionally, wall loss due to electrostatic effects which results in substantial particle deposition in Teflon chambers is not a problem in a metallic flow system (McMurry and Rader 1985).…”

Section: Flow Parametersmentioning

confidence: 98%

A New Aerosol Flow System for Photochemical and Thermal Studies of Tropospheric Aerosols

Ezell

Johnson

et al. 2010

Aerosol Science and Technology

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For studying the formation and photochemical/thermal reactions of aerosols relevant to the troposphere, a unique, high-volume, slow-flow, stainless steel aerosol flow system equipped with UV lamps has been constructed and characterized experimentally. The total flow system length is 8.5 m and includes a 1.2 m section used for mixing, a 6.1 m reaction section and a 1.2 m transition cone at the end. The 45.7 cm diameter results in a smaller surface to volume ratio than is found in many other flow systems and thus reduces the potential contribution from wall reactions. The latter are also reduced by frequent cleaning of the flow tube walls which is made feasible by the ease of disassembly. The flow tube is equipped with ultraviolet lamps for photolysis. This flow system allows continuous sampling under stable conditions, thus increasing the amount Received 3 November 2009; accepted 10 January 2010. We are grateful to the U.S. Department of Energy (Grant # DE-FG02-05ER64000) for support of this work. Additional support was provided by the AirUCI Environmental Molecular Science Institute funded by the National Science Foundation (Grant # CHE-0431312). E.A.B. acknowledges financial support from a National Science Foundation graduate student fellowship. This research was in part in collaboration with the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Address correspondence to Barbara J. Finlayson-Pitts, Department of Chemistry, University of California Irvine, Irvine, CA 92697-2025, USA. E-mail: bjfinlay@uci.edu of sample available for analysis and permitting a wide variety of analytical techniques to be applied simultaneously. The residence time is of the order of an hour, and sampling ports located along the length of the flow tube allow for time-resolved measurements of aerosol and gas-phase products. The system was characterized using both an "inert" gas (CO 2 ) and particles (atomized NaNO 3 ). Instruments interfaced directly to this flow system include a NO x analyzer, an ozone analyzer, relative humidity and temperature probes, a scanning mobility particle sizer spectrometer, an aerodynamic particle sizer spectrometer, a gas chromatograph-mass spectrometer, an integrating nephelometer, and a Fourier transform infrared spectrophotometer equipped with a long path (64 m) cell. Particles collected with impactors and filters at the various sampling ports can be analyzed subsequently by a variety of techniques. Formation of secondary organic aerosol from α-pinene reactions (NO x photooxidation and ozonolysis) are used to demonstrate the capabilities of this new system.

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Turbulent flow and Particle Deposition in the Trachea

Owen

1969

Ciba Foundation Symposium ‐ Circulatory and Respiratory Mass Transport

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Transport of small particles to vertical surfaces

Cited by 190 publications

References 7 publications

Particle deposition in ventilation ducts

Particle deposition in ventilation ducts

A New Aerosol Flow System for Photochemical and Thermal Studies of Tropospheric Aerosols

Turbulent flow and Particle Deposition in the Trachea

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