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Factors Affecting Particle Depositions of Electret Filters Used in Residential HVAC System and Indoor Air Cleaner

Category: Control Techniques and Strategy

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.10.0373

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De-Qiang Chang1,2, Jing-Xian Liu1,2, Sheng-Chieh Chen 3

  • 1 Filter Test Center, College of Resources and Civil Engineering, Northeastern University, Liaoning 110819, China
  • 2 Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China
  • 3 Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA


Modified model predicts penetration well for particle with different charge states.
Parametric analysis using the validated model was conducted.
Analysis clarifies effects of velocity and filter property on efficiency enhancement.
Favorable face velocities for the current electret filter are 0.05-0.2 m s–1.
Thick filter with low solidity performs better than thin filter with high solidity.


Electret, dielectric materials with quasi-permanent electrical charges, filter have been widely applied to control particulate matter (PM) pollutions. However, there is a lack of research on parametric analysis to examine the effects of operation face velocity, charge density, fiber diameter, porosity, thickness, etc., on their performances for a more energy-efficient filtration. A reliable parametric analysis relies on an accurate filtration model. Without any empirical parameters added, a modified model developed earlier by the authors was the first able to accurately predict efficiency of electret filters under different face velocities and filter charge densities for neutralized particles. To further verify the applicability of this model, filtration experiments of monodisperse particles with 3-500 nm diameters through two different electrets, one with 0.075 and the other with 0.025 mC m-2 charge density, for particles and filters with different charge states (i.e., singly charged and neutral particles, and discharged electret filters) were conducted. It was found the modified model was still in good agreement with the experimental data. The validated model was then used to conduct the parametric analysis to clarify the effects of aforementioned parameters on the filter performances. It was found the efficiency enhanced by fiber charges varied largely with varying face velocity and charge density of the electret. The fiber diameter effects analysis showed that under a constant pressure drop thicker filters with lower solidity have a combined positive effect for reducing particle penetration. The analysis results in this work can be applied for future electret filter design and operation.


Electret filter Electrostatic effects Charge density Particulate matter Face velocity

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