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On the efficiency with which aerosol particles of radius larger than 0.1 μm are collected by simple ice crystal plates
Authors:J. J. Martin  P. K. Wang  H. R. Pruppacher  A. E. Hamielec
Affiliation:(1) Department of Atmospheric Sciences, University of California, Los Angeles;(2) Department of Chemical Engineering, McMaster University, Hamilton, Canada
Abstract:A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1lerle10 mgrm are collected by simple ice crystal plates of radius 50leacle640 mgrm in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1lerle1 mgrm. For aerosol particles ofr>1 mgrm the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops.
Keywords:Atmospheric aerosols  Ice crystals  Scavenging
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