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Fine particle losses in cascade impactors
J. AemsolSci. Vol. 7.9, Suppl. 1. pp. S441-S442, 1998 Q 1998 Published by Elsevier Science Ltd. All tights reserved Printed in Great Britain 0021-8502/98 $19.00+ 0.00
Pergamon
FINE PARTICLE LOSSES IN CASCADE IMPACTORS MARK0 MARJAMAKI, ANNELE VIRTANEN and JORMA KESKINEN Tampere University of Technology, Department of Physics, P.O.Box 692 FIN 33101 Tampere, Finland
KEYWORDS Cascade Impactors,
Losses
INTRODUCTION An ideal impactor does not collect particles smaller than the cut diameter of the impactor. In practice, some of these particles are collected on the walls and collection substrates of the impactor because of non-inertial forces. If the amount of these losses is high, measured size distribution can be skewed. Lately there has been interest in finding out the effect of particle charge on the collection efficiencies of the impactors (e.g. Keskinen et. a1.,1992; de Juan et. al., 1997). In this study the losses of small multiply and singly charged particles were measured for two different cascade impactors using the calibration method described by Keskinen et. al. (1998). As a calibration aerosol monodispersed Dioctyl Sebacate (DOS) aerosol was used. The two studied cascade impactors were Berner type Low Pressure Impactor (BLPI) Hauke 25/3 and Dekati cascade impactor. Both impactors have multiple round jets.
RESULTS AND DISCUSSION Losses for both impactors were found to be small, generally less than 0.5%. However losses increase rapidly as the size of the particles decreases. This can be seen from figure 1.
5
0
multiple charged
o
single
charged
-Fit 1 0 0.1 DP (mm)
Figure 1.
Particle
losses in Dekati Low Pressure Impactor (stage #9).
Abstracts
S442
of the 5th International
Aerosol Conference
1998
10 9 8
0.001
Figure 2.
0.01
Dp/Cc
“’
Particle losses in Bemer type Low Pressure Impactor.
Figure 1 shows the losses both for singly and multiply charger particles. Multiply charged particles have been charged by unipolar diffusion charging, producing charge levels ranging from approximately two elementary charges for 0.08 pm particles to 30 elementary charges for 0.7 km particles. This charge level does not seem to have a noticeable effect on the losses. Figure 2 shows fine particle losses of different BLPI stages. Corrected for different operation pressures, the losses are dependent on particle size only. These results suggest that the prominent deposition mechanism is diffusion.
REFERENCES de Juan, L., Brown, S., Serageldin, K., Davis, N., Rose& J., Lazcano, J. and Fernandez de la Mora, J. (1997). J. AerosolSci. 28:1029-1048. Keskinen, J., Pietarinen, K., Lehtirn&i, M. (1992). J. Aerosol Sci. 23:353-360. Keskinen, J., Ma@n&i, (Accepted)
M., Virtanen, A., M&el%, T. and Hillamo, R. (1998) J. Aerosol Sci.
Pergamon
FINE PARTICLE LOSSES IN CASCADE IMPACTORS MARK0 MARJAMAKI, ANNELE VIRTANEN and JORMA KESKINEN Tampere University of Technology, Department of Physics, P.O.Box 692 FIN 33101 Tampere, Finland
KEYWORDS Cascade Impactors,
Losses
INTRODUCTION An ideal impactor does not collect particles smaller than the cut diameter of the impactor. In practice, some of these particles are collected on the walls and collection substrates of the impactor because of non-inertial forces. If the amount of these losses is high, measured size distribution can be skewed. Lately there has been interest in finding out the effect of particle charge on the collection efficiencies of the impactors (e.g. Keskinen et. a1.,1992; de Juan et. al., 1997). In this study the losses of small multiply and singly charged particles were measured for two different cascade impactors using the calibration method described by Keskinen et. al. (1998). As a calibration aerosol monodispersed Dioctyl Sebacate (DOS) aerosol was used. The two studied cascade impactors were Berner type Low Pressure Impactor (BLPI) Hauke 25/3 and Dekati cascade impactor. Both impactors have multiple round jets.
RESULTS AND DISCUSSION Losses for both impactors were found to be small, generally less than 0.5%. However losses increase rapidly as the size of the particles decreases. This can be seen from figure 1.
5
0
multiple charged
o
single
charged
-Fit 1 0 0.1 DP (mm)
Figure 1.
Particle
losses in Dekati Low Pressure Impactor (stage #9).
Abstracts
S442
of the 5th International
Aerosol Conference
1998
10 9 8
0.001
Figure 2.
0.01
Dp/Cc
“’
Particle losses in Bemer type Low Pressure Impactor.
Figure 1 shows the losses both for singly and multiply charger particles. Multiply charged particles have been charged by unipolar diffusion charging, producing charge levels ranging from approximately two elementary charges for 0.08 pm particles to 30 elementary charges for 0.7 km particles. This charge level does not seem to have a noticeable effect on the losses. Figure 2 shows fine particle losses of different BLPI stages. Corrected for different operation pressures, the losses are dependent on particle size only. These results suggest that the prominent deposition mechanism is diffusion.
REFERENCES de Juan, L., Brown, S., Serageldin, K., Davis, N., Rose& J., Lazcano, J. and Fernandez de la Mora, J. (1997). J. AerosolSci. 28:1029-1048. Keskinen, J., Pietarinen, K., Lehtirn&i, M. (1992). J. Aerosol Sci. 23:353-360. Keskinen, J., Ma@n&i, (Accepted)
M., Virtanen, A., M&el%, T. and Hillamo, R. (1998) J. Aerosol Sci.