Influence of cross-flow on particle collection characteristics of multi-nozzle impactors

Fang, C. P.; Marple, Virgil A.; Rubow, Kenneth L.

doi:10.1016/0021-8502(91)90001-x

Cited by 53 publications

(38 citation statements)

References 10 publications

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“…Most of the samplers investigated in this study, however, have multiple round nozzles, with the Millipore Air Tester having as many as 1,000 nozzles. Although it is generally assumed that calculations for a single-nozzle design can be directly applied to multiple nozzle impactors, some studies indicate that cross-flow from neighboring jets influences the particle collection efficiency (Sethuraman and Hickey 2001;Fang et al 1991).…”

Section: Resultsmentioning

confidence: 99%

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Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Yao

Mainelis

2006

Aerosol Science and Technology

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Traditional collection efficiency measurements often directly compare particle concentrations upstream and downstream of the sampler without considering the particle losses. Here, we developed a new approach which tests collection efficiencies of the sampler with and without agar collection plate loaded. This method thus allows estimating the effective collection efficiency, i.e., the fraction of incoming particles deposited onto the agar collection medium only.The experimental cut-off sizes, or d 50 , of the investigated samplers ranged from 1.2 µm for the RCS High Flow, 1.7 µm for the MAS-100, 2.1 µm for SAS Super 180, to 2.3 µm for MAT; for other three samplers they were close to or above 5 µm. In most cases the theoretical d 50 was lower than the experimental value, which was likely due to the dissipation of impactor jets and the influence of cross-flow in the multi-nozzle impactors. For most samplers, we observed a notable difference between the collection efficiency obtained by the traditional measurement method and the effective collection efficiency. In general, all samplers collected 10% or less of 0.5 µm particles onto the agar medium.This study indicates that the use of most of the tested bioaerosol samplers may result in a substantial underestimation of bacterial concentrations, especially of single bacterial cells with diameter 0.5-1.0 µm. On the other hand, most of the investigated samplers would be more efficient when collecting larger fungal spores.

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Section: Resultsmentioning

confidence: 99%

“…Based on their studies with MOUDI impactor, Fang et al (1991) recommended that their-derived cross-flow parameter should be below 1.2. Among the investigated portable samplers, the MAS-100 and the SAS Super 180 had cross-flow parameter of 1.06.…”

Section: Resultsmentioning

confidence: 99%

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Yao

Mainelis

2006

Aerosol Science and Technology

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“…Although this single-nozzle design eliminates the multiple jet interaction problems, 7 particle bounce of particles larger than the cut point was found to be significant. Also, as with the previously described system, this impactor has a 2.1-mm cut point, which is lower than that of the Federal Reference Method (FRM) (2.5 µm).…”

Section: Introductionmentioning

confidence: 91%

Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler

Demokritou

Kavouras

Harrison

et al. 2001

Journal of the Air & Waste Management Association

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A conventional impactor for a particle speciation sampler was developed and validated through laboratory and field tests. The speciation sampler consists of the following components: a PM 2.5 conventional impactor that removes particles larger than 2.5 µm, an all-glass, coated honeycomb diffusion denuder, and a 47-mm filter pack. The speciation sampler can operate at two different sampling rates: 10 and 16.7 L/min. An experimental characterization of the impactor's performance was conducted. The impactor's collection efficiency was examined as a function of critical design parameters such as Reynolds number, the distance from the nozzle exit to the impaction plate, and the impaction substrate coating method. The bounce of particles larger than the cut point was successfully minimized by using a greased surface as the impaction substrate. Additionally, a series of field intercomparison experiments were conducted at both 10 and 16.7 L/min airflow. PM 2.5 mass and SO 4 2-concentrations were measured and compared with the Federal Reference Method (FRM) and found to be in good agreement. Results of the laboratory chamber tests also indicated that the impactor's performance was in good agreement with the FRM.

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“…Nearly all the theoretical work and much of the experimental work have been conducted on single nozzle impactors. The results of single-nozzle impactor analysis have often been applied to multinozzle impactors which are assumed to act as a group of individual nozzles (Fang et al 1991;Kwon et al 2002). However, this approach ignores an important fact that the interaction between the flows from adjacent nozzles can change the fluid mechanics in the impaction region, the location of the jet stagnation points, and the impaction characteristics of each nozzle.…”

Section: Introductionmentioning

confidence: 99%

“…However, this approach ignores an important fact that the interaction between the flows from adjacent nozzles can change the fluid mechanics in the impaction region, the location of the jet stagnation points, and the impaction characteristics of each nozzle. The particle collection efficiency was found to be influenced by the cross flow (Fang et al 1991) and nozzle arrangement (Kwon et al 2002). Moreover, the effect of the S/W ratio on the cutoff characteristics of the multinozzle impactors (i.e., micro-orifice impactors) has been studied (Gudmundsson et al 1995;Kwon et al 2002;Yao and Mainelis 2006).…”

Section: Introductionmentioning

confidence: 99%

Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions

Chien

Tien

Liu

et al. 2015

Aerosol Science and Technology

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The NCTU micro-orifice cascade impactor (NMCI) was redesigned and tested to enable the measurement and adjustment of the jet-to-plate distance (S) of the impactors by using a micrometer. Each stage of the NMCI contains an impaction plate and a nozzle plate which are separated. The bottom casing for impaction plate assembly and the nozzle plate holder of each stage are separated. Calibration results show that the cutoff aerodynamic diameter (d pa50 ) of the three lower stages (d pa50 D 180, 100, and 56 nm) are close to the nominal values given in Marple et al. (1991). In addition, the S/W (W: nozzle diameter) effects on the d pa50 for the three lower stages were investigated and an empirical equation was developed to facilitate the prediction of d pa50 when the nozzle diameters may change slightly from one batch to another. The relationship between the nozzle diameter and pressure drop of the micro-orifice impactors at the fixed operational flow rate of 30 L/min was also established so that the nozzle diameters can be predicted from the pressure drop measurement. An empirical equation was proposed to express the correlation between the dimensionless cutoff size and the S/W ratio when considering isentropic flow to facilitate the design of microorifice impactors for S/W > 4. It is expected that the present NMCI could improve the accuracy of size classification of submicron particles below 180 nm, especially for nanoparticles.

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Influence of cross-flow on particle collection characteristics of multi-nozzle impactors

Cited by 53 publications

References 10 publications

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler

Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions

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Influence of cross-flow on particle collection characteristics of multi-nozzle impactors

Cited by 53 publications

References 10 publications

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

Development and Evaluation of an Impactor for a PM2.5Speciation Sampler

Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions

Contact Info

Product

Resources

About

Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler