Experimental study of diffusion charging of aerosols

Technical Report · Mon Mar 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7356886· OSTI ID:7356886

Pui, D Y.H.

The electrical charging of aerosol particles by unipolar gaseous ions was studied theoretically and experimentally. The primary objective of the study was to make precise determinations of the aerosol particle charge under various conditions of charging and to compare the experimental results with those predicted by theory. Experiments were performed using monodisperse oleic acid aerosols generated by a vibrating orifice generator, monodisperse NaCl and DOP (di-octyl phthalate) aerosols generated by an electrostatic classification method, and sulfuric acid aerosols generated by the photo-chemical conversion of gaseous SO/sub 2/ in the smog chamber. The experiments covered a particle size range of 0.0075 ..mu..m to 5.04 ..mu..m diameter. The corresponding range in Knudsen number (Kn = lambda/sub i//a, lambda/sub i/ = mean free path of ions, a = particle radius) was from 0.0056 to 3.86. The charging parameter, n/sub 0/t, was varied between 2.56 x 10/sup 6/ to 5.1 x 10/sup 7/ ion-s/cc, where n/sub 0/ is the concentration of ions and t is the charging time. Comparisons of the results with available aerosol charging theories indicate that there is reasonable agreement between the theory and experiment in the continuum regime (Kn << 1) where the classical Fuchs--Pluvinage equation is expected to apply. However, in the free molecular (Kn >> 1) and the transition regimes (Kn approx. or equal to 1), where the ion mean free path is no longer small in comparison with particle size, there is considerable discrepancy between the experimental data and available charging theories. A semi-empirical equation was developed which agrees well with the experimental data over the entire range of particle size and charging parameters covered in the experiments. Theoretical results are presented showing the distribution of charges on the particles as a function of particle size and the charging parameter n/sub 0/t. 70 figures, 24 tables, 112 references. (auth)

• Research Organization: Minnesota Univ., Minneapolis (USA). Particle Technology Lab.
• OSTI ID: 7356886
• Report Number(s): COO-1248-49
• Country of Publication: United States
• Language: English

Related Subjects

500100* -- Environment
Atmospheric-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
AEROSOLS
AIR POLLUTION
ALKALI METAL COMPOUNDS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHARGE EXCHANGE
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
COLLISIONS
COLLOIDS
DISPERSIONS
DISTRIBUTION
ELECTRIC CHARGES
FLUID FLOW
FLUIDS
GAS FLOW
GASES
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ION COLLISIONS
IONS
KNUDSEN FLOW
MONOCARBOXYLIC ACIDS
OLEIC ACID
ORGANIC ACIDS
ORGANIC COMPOUNDS
PARTICLE SIZE
PHTHALATES
POLLUTION
SIZE
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLS
SULFURIC ACID