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The Influence of Air Flow Velocity and Particle Size on the Collection Efficiency of Passive Electrostatic Aerosol Samplers

Category: Aerosol Physics and Instrumentation

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.06.0211
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R.J. Imani1, L. Ladhani2, G. Pardon2, W.V. Wijngaart2, E. Robert 3

  • 1 Department of Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
  • 2 Department of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm, Sweden
  • 3 Department of Mechanical Engineering, Polytechnique Montréal, Montréal, Quebéc, Canada

Highlights

The collection efficiency of two passive electrostatic transducers is evaluated.
The parameters investigated include particle size and bulk flow velocity.
One of the samplers investigated allows particle collection directly to liquid.
The presence of recirculation zones enhances collection efficiency for submicron particles.


Abstract

Electrostatic sampling is a promising method for the collection of bioaerosol particles. Although the underlying physics responsible for particle collection are well understood, the collection efficiency of simple passive electrostatic samplers is difficult to predict. Under these conditions, the collection efficiency becomes very sensitive to ambient air current and particle size, especially for submicron particles relevant for airborne virus transmission. In this paper, we compare two electrostatic aerosol sampler designs, a commercial product consisting of a flat collector plate located in the same plane as the charging needles and an axisymmetric design sampling directly to a liquid droplet. The aerosol particle collection efficiency of the samplers is investigated for particle size ranging from 0.25 to 2 µm while the air flow velocity surrounding the samplers is varied from 0.3 to 1 m/s. For the planar design, at all ambient flow velocities, the submicron fraction of the particles captured originates in streamlines up to a maximum of 75 mm above the surface of the device collector, which greatly limits the volume of air being effectively sampled. The axisymmetric design features a non-monotonic capture efficiency as a function of particle size, with a minimum between 0.4 and 0.8 m. The flow field in the inter-electrode region, captured using particle image velocimetry (PIV) reveals the presence of strong recirculation zones that can be responsible for the increased collection efficiency for very small particles.

Keywords

Electrostatic precipitation Submicron particles Quantitative Sampling PIV


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