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Electret Filtration Mechanisms and Important Parameters

Explore the important parameters and filtration mechanisms for electret filters, including mechanical and electrostatic mechanisms. Understand the performance and real-life effectiveness of charged media. Consider the influence of temperature, humidity, and environmental conditions on electret filters.

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Electret Filtration Mechanisms and Important Parameters

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  1. Electret, What Are The Important Parameters That Need To Be Considered Presented at 2005 NAFA Annual Convention September 23, 2005 by Ker-Ching (K.C.) Hsieh, Ph,D. Particle Tech, Inc. St Paul. MN

  2. Filtration Mechanisms For Electret • Mechanical Filtration Mechanisms • Diffusion • Interception • Inertial Impaction • Electrostatic Filtration Mechanisms • Dielectricphoretic Effect/Force • Columbic Force • Image Force

  3. Performance Of A Chargeable Media If It Is Not Charged

  4. Performance Of A Chargeable Media After It Is Charged

  5. Net Effect—Higher Average Life Time Efficiency

  6. Examples

  7. Particle Deposition On A Single Fiber

  8. Possible Gradient Structure

  9. Important Parameters Need To Be Considered For Electret • Initial efficiency • Initial efficiency without charge • Shelf life performance • Environmental conditions • Special parameters • aerosol contains alcohol, alcohol vapor and other chemicals, oily aerosol, combustion generated aerosol…..

  10. Electrostatic Index

  11. Examples EI1

  12. Initial Efficiency With And Without Charges

  13. Shelf Life Tests

  14. Temperature Effect

  15. Humidity Effect

  16. Effect of High Temperature and High Humidity

  17. Real Life Performance of Electret : 1

  18. Real Life Performance of Electret: 1

  19. Real Life Performance of Electret: 1

  20. Real Life Performance of Electret: 2

  21. Real Life Performance of Electret: 2

  22. Cigarette Smoke Test

  23. Cigarette Smoke Test

  24. Summary • Charged media are “quite different” from non-charged media. • Charged media have a completely different set of parameters that need to be considered when they are used. • Is it premature for ASHRAE 52.2 to try to use a simplified method to try to compare charged filters and non-charged filters?

  25. Summary • Is the “conditioning” step going to solve the disputes between the charged media manufacturers and non-charged media manufacturers? Answer: “No”, on the other hand, it will bring in a whole new set of problems. • “MERV” is strange enough, please don’t make things more confusing by adding this conditioning step.

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