Ramin Jajarmi Imani1, Laila Ladhani2, Gaspar Pardon2, Wouter van der Wijngaart2, Etienne Robert 3


Department of Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
Department of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm, Sweden
Department of Mechanical Engineering, Polytechnique Montréal, Montréal, Québec, Canada



Received: June 6, 2018
Revised: September 15, 2018
Accepted: September 29, 2018
Download Citation: ||https://doi.org/10.4209/aaqr.2018.06.0211 


Cite this article:
Imani, R.J., Ladhani, L., Pardon, G., van der Wijngaart, W. and Robert, E. (2019). The Influence of Air Flow Velocity and Particle Size on the Collection Efficiency of Passive Electrostatic Aerosol Samplers. Aerosol Air Qual. Res. 19: 195-203. https://doi.org/10.4209/aaqr.2018.06.0211


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–1. 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 µm. 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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