Depostition of submicron aerosol particles in turbulent and transitional flow

Okuyama, Kikuo; Asai, Masahito

doi:10.1002/aic.690390104

Cited by 39 publications

(15 citation statements)

References 23 publications

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“…Chamberlain et al (1984) made a single observation of deposition in the diffusion regime. Shimada et al (1993) provided a larger data set of reasonable quality for deposition in the diffusion regime, showing increasing deposition for decreasing particle size. The data of Wells & Chamberlain and Shimada et al are displayed in Figure 2.1.…”

Section: 33a Particle Size and Air Velocitymentioning

confidence: 99%

“…Shimada et al (1993) (1977) who derived a theoretical expression for diffusional deposition from pipe flow assuming the particle eddy diffusivity, ξ p , to be equal to Lin et al's (1953) with the experimental data. Because particles that are strongly influenced by Brownian motion are insignificantly affected by gravity, these equations for the diffusion regime may be applied equally to horizontal and vertical surfaces.…”

Section: 53a Empirical Equations In the Diffusion Regimementioning

confidence: 99%

“…et al ( ) Cheong (1997 Figure 2.9 Experimental data for polydisperse aerosols depositing in large horizontal ducts measured by inferring deposition from differences in concentration measurements. Durst et al (1995) Re = 15,800 (Moser et al, 1999) Re = 25,000 (Moser et al, 1999) equation (2.90), Davies (1966b) dimensionless distance from the wall, y + (-) (Shaw & Hanratty, 1977) equation (2.61) (Shimada et al, 1993) Figure 2.18 Comparison of empirical expressions for deposition to smooth surfaces in the diffusion regime. equation (2.67) (Gieseke et al, 1980) equation (2.68) (Kvasnak & Ahmadi, 1996) ceiling, equation (2.73) (Kvasnak & Ahmadi, 1996) floor, equation (2.65) (Papavergos & Hedley, 1984) ceiling, equation (2.66) (Papavergos & Hedley, 1984) In steel ducts, particle deposition rates were higher to the floor than to the wall, which, in turn, were greater than to the duct ceiling.…”

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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 Velocitymentioning

confidence: 99%

Section: 53a Empirical Equations In the Diffusion Regimementioning

confidence: 99%

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Particle deposition in ventilation ducts

Sippola¹

2002

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Section: Particle Size and Air Velocitymentioning

confidence: 99%

“…This figure illustrates the importance of particle size, as measured by τ + , in determining particle deposition. The data of Shimada et al (1993) for deposition from a horizontal tube is included so as to extend the lower range of τ + and to illustrate the trends in deposition as τ + becomes very small. (The effect of gravity on deposition from this horizontal flow is expected to be negligible owing to the very small particle sizes, d p = 0.01-0.04 µm, used in these experiments.…”

Section: Experimental Data From Straight Tubes and Ductsmentioning

confidence: 99%

Particle deposition from turbulent flow: Review of published research and its applicability to ventilation ducts in commercial buildings

Sippola¹,

Nazaroff²

2002

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This report reviews published experimental and theoretical investigations of particle deposition from turbulent flows and considers the applicability of this body of work to the specific case of particle deposition from flows in the ducts of heating, ventilating and air conditioning (HVAC) systems. Particle deposition can detrimentally affect the performance of HVAC systems and it influences the exposure of building occupants to a variety of air pollutants.The first section of this report describes the types of HVAC systems under consideration and discusses the components, materials and operating parameters commonly found in these systems. The second section reviews published experimental investigations of particle deposition rates from turbulent flows and considers the ramifications of the experimental evidence with respect to HVAC ducts. The third section considers the structure of turbulent airflows in ventilation ducts with a particular emphasis on turbulence investigations that have been used as a basis for particle deposition models.The final section reviews published literature on predicting particle deposition rates from turbulent flows.A large quantity of experimental data regarding particle deposition from turbulent flows has been collected using a range of techniques of varying quality. Nearly all of these data have been collected from straight tubes or ducts with a fully developed turbulent flow profile and the data are widely scattered. Most of the data of acceptable quality have been collected from tubes or ducts with hydraulic diameters much smaller than ducts in typical HVAC systems. Particle deposition from turbulent flow with a developing flow profile has not been systematically investigated and only two investigations of particle deposition from turbulent flow through bends have been published. Developing turbulent flow profiles and bends are common in HVAC ducts.Owing to the large number of investigations into particle deposition from turbulent flow, much is known; however, the direct applicability to the case of particles in HVAC ducts is limited. Particle size, turbulence intensity and the roughness and orientation (horizontal or vertical) of the deposition surface are the parameters that control particle deposition rates and all of these factors are likely to be pertinent in HVAC ducts. Particle diameters of concern in HVAC ducts range from about 0.003 to 30 µm and deposition rates are known to vary strongly in this range. Friction velocities in HVAC ducts are iii likely to be in the range 0.1-1 m/s and variations of turbulence intensities in this range are likely to influence deposition rates. Both microscale surface roughness (from less than 1 micron up to hundreds of microns) and macroscale roughness (about 1 mm and larger) have been demonstrated to enhance particle deposition relative to the case of a smooth surface. Microscale roughness intrinsic to the duct material, or due to corrosion or previous deposition of particles, and macroscale roughness from thermal insulation, joi...

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