Aerosol Deposition From Turbulent Airstreams in Vertical Conduits.

Sehmel, G.A.

doi:10.2172/4549565

Cited by 45 publications

(30 citation statements)

References 17 publications

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“…Adam et al where, again, an average particle diameter of 1.5 µm was assumed to enable presentation of the data in this form. These data also seem inconsistent with previously observed trends and the inconsistencies are likely to be a consequence of the unreliable methods inlet has been observed to be greater than that in fully developed flow (Chamberlain, 1967;Sehmel, 1968;Ilori, 1971). Occasionally the opposite trend has been observed (Friedlander & Johnstone, 1957;Liu & Agarwal, 1974).…”

Section: Relevance Of Current Data To Deposition In Ventilation Ductscontrasting

confidence: 80%

“…Their data showed increased particle deposition with increases in air velocity and particle diameter for particles in the diffusion-impaction regime. Subsequent measurements of deposition 39 from small diameter tubes have confirmed these findings (Postma & Schwendiman, 1960;Sehmel, 1968;Liu & Agarwal, 1974).…”

Section: 33a Particle Size and Air Velocitymentioning

confidence: 79%

“…The way such coatings may influence deposition from the standpoint of microscale roughness is not apparent. Evidence of particle bounce or reentrainment has been observed in some experiments (Friedlander & Johnstone, 1957;Postma & Schwendiman, 1960;Chamberlain, 1967;Sehmel, 1968;Rouhiainen & Stachiewicz, 1970). When observed, these phenomena have usually been greater for larger particle sizes and higher air speeds.…”

Section: Details About Experiments In Straight Tubes and Ductsmentioning

confidence: 87%

“…Sehmel (1968) classified some pipes in his study as smooth or rough based on a visual inspection. In the two reported experimental runs comparing smooth and rough pipes, the deposition rate to the rough pipe was larger than to the smooth pipe in one case, and the deposition rates were equal in the other case.…”

Section: 33b Microscale Roughnessmentioning

confidence: 99%

“…In this model, he proposed that the particle eddy diffusivity is greater than the eddy viscosity. By correlating the available experimental deposition data (Stavropolous, 1954;Friedlander & Johnstone, 1957;Postma & Schwendiman, 1960;Sehmel, 1968), he arrived at an expression for the particle eddy diffusivity for a particle depositing to a smooth vertical wall of…”

Section: 54c Gradient Diffusion Modelsmentioning

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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