AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Nanoparticle Loading and Agglomeration in Charged and Discharged Electret Filter Media
JAMES MONTGOMERY, Steven Rogak, Sheldon Green, University of British Columbia
Abstract Number: 734 Working Group: Indoor Aerosols
Abstract Airborne ultrafine particulate has been shown to cause adverse health effects when inhaled. This has led to an increased interest in the filtration of these particles by fibrous filters such as those commonly used in building HVAC systems. The characteristics of particle agglomerates have been shown to affect the evolution of flow resistance and filter efficiency but little is known about the characteristics of nanoparticle agglomerations within commercial filter media.
This work provides a comparison of dust accumulation and particle agglomerates from nanoparticles (mean diameter 100nm) within commercial HVAC filter media. The media compared utilizes an electrostatic charge on the fibers to improve filtration efficiency. Tests were performed on the media for both the charged condition and discharged condition; where the charge was removed by immersion in isopropyl alcohol (IPA). Analysis of SEM images of the loaded filters was used to compare particle agglomerates and dust holding properties of the charged and discharged filter media.
Particle agglomerates on the discharged fiber surfaces were found to have a more dense, collapsed structure when compared to the agglomerates on charged fiber surfaces, which grew as thin dendrites. The discharged filter media was also found to be proportionally more heavily loaded with particulate on the upstream side of the filter, which resulted in less dust holding capacity to a given increase in flow resistance. A comparison of the degree of filter loading after an added pressure drop due to dust loading of 4x the original clean filter pressure drop showed that the discharged filter contained ~20% less dust by mass. The degree of fiber surface coverage on the upstream side of the filter was found to be higher for the discharged filter media (12%) compared to the charged filter media (7%).