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Distortion of Size Distributions by Condensation and Evaporation in Aerosol Instruments

Biswas, Pratim and Jones, Carol L. and Flagan, Richard C. (1987) Distortion of Size Distributions by Condensation and Evaporation in Aerosol Instruments. Aerosol Science and Technology, 7 (2). pp. 231-246. ISSN 0278-6826. doi:10.1080/02786828708959161.

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Aerosols that contain volatile species or condensable vapors may be altered by changes in temperature, pressure, and vapor concentration. When such changes occur within aerosol sampling instruments, the measured size distribution can be distorted significantly. The distortion of particle size distributions in a number of commonly used aerosol instruments, including cascade impactors, both conventional and low pressure instruments, and optical particle counters, is explored both theoretically and experimentally in this paper. Ammonium sulfate aerosols in humid atmospheres have been used to test the instruments. In a low pressure impactor in which the pressure is intentionally reduced to facilitate the collection of small particles, a water containing particle may shrink due to evaporation as the pressure is reduced. However, if the sample flow is also accelerated to high velocities, aerodynamic cooling can lead to condensation of water vapor and particle growth. Either of these competing effects may lead to erroneous estimates of the particle size distribution. Optical particle counters generally use a recirculated sheath airflow. Pumps and electrical dissipation heat this air, leading to a temperature increase that shifts the vapor equilibrium, causing a decrease in particle size due to evaporation. Modifications have been made to avoid this distortion in measured size distributions.

Item Type:Article
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Flagan, Richard C.0000-0001-5690-770X
Additional Information:© 1987 American Association for Aerosol Research. Received May 1986; accepted 28 October 1986 This research was supported by Environmental Protection Agency Grants R-809191 and 810857. The conclusions represent the views of the authors and do not necessarily represent the opinion, policies, or recomendation of the U.S. Environmental Protection Agency.
Funding AgencyGrant Number
Environmental Protection Agency (EPA)R-809191010
Environmental Protection Agency (EPA)R-810857
Issue or Number:2
Record Number:CaltechAUTHORS:20150630-170058965
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58721
Deposited By: Irina Meininger
Deposited On:08 Sep 2015 19:58
Last Modified:10 Nov 2021 22:09

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