A general equation for aerosol aspiration by thin-walled sampling probes in calm and moving air

Grinshpun, Sergey A.; Willeke, Klaus; Kalatoor, Suresh

doi:10.1016/0960-1686(93)90132-i

Cited by 67 publications

(40 citation statements)

References 23 publications

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“…A4) is not valid for the second part of the CLACE 2010 period, when the FM-100 was installed with its inlet facing downwards (zenith angle φ = 115 • ). Though, Grinshpun et al (1993) only excluded angles larger than 90 • because it was not common to use an inlet facing downwards. However, V ts U cos φ correctly describes the sedimentation even if the zenith angle is larger than 90 • .…”

Section: Application Of the Corrections For Particle Losses To The Fmmentioning

confidence: 99%

“…For the calm air regime, we decided to use the empirical equation deduced by Grinshpun et al (1993) based on several experiments, as the one by Vincent (2004, 2005) is only applicable for aspiration efficiencies larger than 0.75 and the alternative one by Dunnett and Wen (2002) was numerically deduced for larger particle diameters (40 µm to 110 µm):…”

Section: A1 Aspiration Efficiencymentioning

confidence: 99%

“…So we choose the boundaries such that they fill the gap between calm air and slow moving air (0.5 m s −1 ≤ U 0 and R v ≤ 0.5). The formulas used are based on the work by Grinshpun et al (1993Grinshpun et al ( , 1994:…”

Section: A1 Aspiration Efficiencymentioning

confidence: 99%

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Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100)

Spiegel¹,

Zieger²,

Bukowiecki³

et al. 2012

Atmos. Meas. Tech.

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Abstract. Droplet size spectra measurements are crucial to obtain a quantitative microphysical description of clouds and fog. However, cloud droplet size measurements are subject to various uncertainties. This work focuses on the error analysis of two key measurement uncertainties arising during cloud droplet size measurements with a conventional droplet size spectrometer (FM-100): first, we addressed the precision with which droplets can be sized with the FM-100 on the basis of the Mie theory. We deduced error assumptions and proposed a new method on how to correct measured size distributions for these errors by redistributing the measured droplet size distribution using a stochastic approach. Second, based on a literature study, we summarized corrections for particle losses during sampling with the FM-100. We applied both corrections to cloud droplet size spectra measured at the high alpine site Jungfraujoch for a temperature range from 0 • C to 11 • C. We showed that Mie scattering led to spikes in the droplet size distributions using the default sizing procedure, while the new stochastic approach reproduced the ambient size distribution adequately. A detailed analysis of the FM-100 sampling efficiency revealed that particle losses were typically below 10 % for droplet diameters up to 10 µm. For larger droplets, particle losses can increase up to 90 % for the largest droplets of 50 µm at ambient wind speeds below 4.4 m s −1 and even to >90 % for larger angles between the instrument orientation and the wind vector (sampling angle) at higher wind speeds. Comparisons of the FM-100 to other reference instruments revealed that the total liquid water content (LWC) measured by the FM-100 was more sensitive to particle losses than to re-sizing based on Mie scattering, while the total number concentration was only marginally influenced by particle losses. Consequently, for further LWC measurements with the FM-100 we strongly recommend to consider (1) the error arising due to Mie scattering, and (2) the particle losses, especially for larger droplets depending on the set-up and wind conditions.

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Section: Application Of the Corrections For Particle Losses To The Fmmentioning

confidence: 99%

Section: A1 Aspiration Efficiencymentioning

confidence: 99%

See 1 more Smart Citation

Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100)

Spiegel¹,

Zieger²,

Bukowiecki³

et al. 2012

Atmos. Meas. Tech.

View full text Add to dashboard Cite

show abstract

“…In the case of calm air sampling such models have been restricted by the lack of experimental data with which to validate them Grinshpun et al (1993) explored a general equation for aspiration efficiency which could be applied to moving and calm air for a thin-walled sampler. In the case of calm air the model was restricted to a sampling orientation of 0 ≤ θ ≤ 90 where θ was the angle the sampler axis made with the vertical.…”

Section: Sampler Pointing Upwardsmentioning

confidence: 99%

A Numerical Study of Calm Air Sampling with a Blunt Sampler

Dunnett

Wen

Zaripov

et al. 2006

Aerosol Science and Technology

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It is found that in the case of upwards sampling the bluntness of the sampler only has a significant effect upon aspiration for large sampling velocities, values that would not generally be physically realistic. In the case of downwards sampling an important nondimensional quantity, B 2 R C , is identified, where B represents the sampler bluntness and R C represents the gravitational effects. This quantity determines the physical conditions for which aspiration will not occur and also the limiting values of the aspiration efficiency when aspiration does occur. In the case of low sampling velocities a difference is noted between experimental and numerical results for aspiration efficiency raising the need for more experimental data in this area. For both upwards and downwards sampling the semi-empirical models of Su and Vincent (2004b) have been modified to account for the information gained from the study. This is particularly important in the downwards sampling case where the modified model is found to agree particularly well with the results obtained.

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“…If it is used at a flow rate higher than 3.5 l/min, the CIS will no longer aspirate the inhalable fraction of the external aerosol; however, this is not an issue for its application to PM 2.5 sampling. Theoretical calculations of aspiration, using, e.g., the method of Grinshpun et al (1993 ), indicate that the CIS should aspirate all particles of interest to the PM 2.5 range with greater than 97% efficiency, even at flow rates of up to 20 l/ min.…”

Section: New Sampler Designmentioning

confidence: 99%

Design and validation of a high-flow personal sampler for PM2.5

Adams

Kenny

Nieuwenhuijsen

et al. 2001

J Expo Sci Environ Epidemiol

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A high -flow personal sampler ( HFPS ) for airborne particulate matter has been developed and fully characterised, and validation tests have been carried out. The sampler is a low -cost gravimetric instrument designed to collect particulate matter with a 50% cut point at 2.5 m aerodynamic equivalent diameter ( PM 2.5 ) , where size selection is achieved by the use of porous polyurethane foam. Development of a porous foam selector was chosen over a cyclone or impactor due to the lightweight, low -cost, and compact design that could be achieved. The sampler flow rate of 16 l / min is achieved using a portable, flowcontrolled pump; this flow rate is far higher than that of conventional personal samplers and the HFPS can therefore be used for personal sampling in the ambient environment over short sampling periods of much less than 24 h. The HFPS is currently being used in a study of particle exposure of urban transport users ( cyclists, car drivers, bus and Underground rail passengers ) where personal sampling over short time periods representing typical commuter journey times is required. The HFPS was fully characterised in chamber studies with a TSI aerodynamic particle sizer ( APS ) . The sampler was then validated against a co -located U.S. EPA Federal Reference PM 2.5 Well Impactor Ninety Six ( WINS ) and a KTL cyclone, and parallel testing was performed. Initial testing showed some penetration of particles through the porous foam structure; applying an oil coating to the foam eliminated this problem. Chamber testing was carried out on a number of different selector prototypes, with the final design giving a 50% penetration diameter ( i.e., d 50 ) of 2.4 m at 16 l / min. The new sampler exhibited good agreement in three sets of co -located tests with established samplers, and parallel testing showed excellent agreement between paired HFPS samplers.

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A general equation for aerosol aspiration by thin-walled sampling probes in calm and moving air

Cited by 67 publications

References 23 publications

Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100)

Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100)

A Numerical Study of Calm Air Sampling with a Blunt Sampler

Design and validation of a high-flow personal sampler for PM2.5

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