Theoretical Study of Aerosol Filtration by Fibrous Filters

Lee, K. W.; Liu, B. Y. H.

doi:10.1080/02786828208958584

Cited by 490 publications

(327 citation statements)

References 12 publications

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“…Another possible method to study theoretically diffusional filtration of nanoparticles is the Brownian dynamics technique (Lagrangian approach) based on stochastic simulations of aerosol particles' trajectories. Results obtained in such a way by Podgórski (2002) and by Bałazy and Podgórski (2007) agreed-as for the functional structure-with the form of expression for E D derived by Lee and Liu (1982), i.e., with the term (1 − α) 1/3 retained, but at the same time the use of the numerical constant C d = 2.9 instead of 2.6, as suggested by other researches, yielded a somewhat better agreement. Thus, here we will use the following theoretical formula for the single fiber deposition efficiency due to Brownian diffusion:…”

Section: Classical Description For Homogeneous Filtersupporting

confidence: 68%

“…[8] Lee and Liu (1982) also derived a theoretical expression for the single fiber efficiency related to the direct interception, E R , that accounts for a non-zero particle size (a "point-particle" model is commonly assumed when formulating boundary conditions at the fiber surface in classical diffusion theory); their compact result reads as:…”

Section: Classical Description For Homogeneous Filtermentioning

confidence: 99%

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Penetration of Monodisperse, Singly Charged Nanoparticles through Polydisperse Fibrous Filters

Podgórski

Maisser

Szymanski

et al. 2011

Aerosol Science and Technology

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The article presents experimental results and theoretical analysis of aerosol nanoparticle penetration through fibrous filters with a broad fiber diameter distribution. Four fibrous filters were produced using the melt-blown technique. The analysis of the filters' SEM images indicated that they had log-normal fiber diameter distribution. Five kinds of proteins and two types of silica particles were generated by electrospraying and were then classified using a Parallel Differential Mobility Analyzer to obtain well-defined, monodisperse, singly charged challenge aerosols with diameters ranging from 6.3 to 27.2 nm. Particle penetration through the filters was determined using a water-based CPC. Experimental results were compared first with predictions derived from the classical theory of aerosol filtration. It is demonstrated that it is inappropriate to apply it to the arithmetic mean fiber diameter, as this results in turn in a huge underestimation of nanoparticle penetration. A better, but still unsatisfactory agreement is observed when that theory was used together with the pressure drop equivalent fiber diameter or when the Kirsch model of nonuniform fibrous media was applied. We show that the classical theory applied to any fixed fiber diameter predicts a stronger dependence of nanoparticle penetration on the Peclet number as compared to experimental data. All these observations were successfully explained by using our original partially segregated flow model that accounts for the filter fiber diameter distribution. It was found that the parameter of aerosol segregation intensity inside inhomogeneous filters increases with the increase in particle size, when the convective transport becomes more pronounced in comparison to the diffusive one.

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Section: Classical Description For Homogeneous Filtersupporting

confidence: 68%

Section: Classical Description For Homogeneous Filtermentioning

confidence: 99%

Penetration of Monodisperse, Singly Charged Nanoparticles through Polydisperse Fibrous Filters

Podgórski

Maisser

Szymanski

et al. 2011

Aerosol Science and Technology

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“…Therefore, the dust loading posed the positive effect on the enhancement of overall filtration efficiency. This finding is consistent to the theoretical result (Lee and Liu, 1982) but slightly different from the previous result on vehicle cabin air filter (Xu et al, 2011), in which the filtration efficiency increases most for smallest particles. no dust load 300 g 600 g 850 g 1000 g Fig.…”

Section: Filter Characteristics Change Along Filter Usage Periodsupporting

confidence: 80%

“…Filtration efficiency demonstrated a characteristic "U" shape with a Most Penetrating Particle Size (MPPS) at approximately 150 nm for Filter A and 55 nm for Filter B, respectively. The U-shape curves were similarly observed from previous experimental studies Xu et al, 2011) and theoretical simulation (Lee and Liu, 1982). Impaction and interception are the dominant filtration mechanisms for larger particles while diffusion is the dominant one for smaller particles.…”

Section: Test Protocols and Data Analysissupporting

confidence: 71%

Investigation of the Performance of Airliner Cabin Air Filters throughout Lifetime Usage

Liu

Ren

et al. 2013

Aerosol Air Qual. Res.

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The air supply from an airliner ventilation system is a mixture of outside air and recirculated air that passes through a high efficiency particulate air (HEPA) filter. The effectiveness of two commercial-available airliner cabin air filters were investigated in laboratory-based measurements due to the practical restrictions on airliner cabin filter testing during usage. The filtration efficiency and pressure drop were assessed at a particle size range of 20-500 nm under various airflow rates throughout the filter usage period. The Most Penetrating Particle Sizes (MPPS) were observed at ~150 and ~55 nm, where the filtration efficiency was 86% and 99% at the rated airflow rates (1600 m 3 /h and 1970 m 3 /h), respectively. The filtration efficiency decreased in response to the increased airflow rate from 1000 m 3 /h to 2200 m 3 /h, with the greatest reduction (~10%) occurring at MPPS. An increase of 250 Pa in the pressure drop across the filter was observed as the airflow rate increased from 1000 m 3 /h to 2200 m 3 /h. Increased filter usage led to increases in both filtration efficiency and the pressure drop. The actual filter usage was estimated using dust loading in the laboratory. Filtration efficiency increased ~10% and the pressure drop increased ~800% when 220 g/m 2 dust was loaded on the filer, corresponding to ~6000 hours filter usage at an in-cabin PM 10 concentration of 100 μg/m 3 . Explicit relationships among filtration efficiency, pressure drop and filter usage under various in-cabin particle concentrations are presented as a reference to facilitate the use of more appropriate airliner cabin air filter exchange periods.

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“…Therefore, the FOA3 SN-C BC correlation, based on ∼100 nm BC, is inconsistent with the observed size distribution of aircraft-generated BC. It is generally understood that the filtration efficiency depends upon filter characteristics (e.g., fiber diameter, solidity, and thickness), flow rate, and particle size (Lee and Liu 1982;Wang and Otani 2013). The filtration efficiency of the specified filter for aircraft SN measurements has not previously been characterized so it is not currently possible to infer the BC mass collection efficiency for different PSDs.…”

Section: Introductionmentioning

confidence: 99%

Updated Correlation Between Aircraft Smoke Number and Black Carbon Concentration

Stettler

Swanson

Barrett

et al. 2013

Aerosol Science and Technology

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Theoretical Study of Aerosol Filtration by Fibrous Filters

Cited by 490 publications

References 12 publications

Penetration of Monodisperse, Singly Charged Nanoparticles through Polydisperse Fibrous Filters

Penetration of Monodisperse, Singly Charged Nanoparticles through Polydisperse Fibrous Filters

Investigation of the Performance of Airliner Cabin Air Filters throughout Lifetime Usage

Updated Correlation Between Aircraft Smoke Number and Black Carbon Concentration

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