AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, 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: 142 Working Group: Indoor Aerosols
Abstract Inhalation of ultrafine particles (UFP) has been linked to detrimental health impacts. There is an interest in the use of fibrous air filters as a means of preventing exposure to UFPs but little is known with regards to the filtration characteristics of fibrous filters challenged with UFPs. The characteristics of particle agglomerate structures have been shown to impact the increase in flow resistance as a function of particle load, but the agglomeration characteristics of UFPs within fibrous filters remains unstudied.
This work provides a comparison of dust accumulation and particle agglomerates from UFPs (mean diameter 100nm) within commercial HVAC electret filter media. Tests were performed on the media for both the charged and discharged conditions. Ongoing work includes investigation of the impact of an upstream nanofiber web on particle structure. Analysis of SEM images and X-ray nanoCT scans of the loaded filters was used to compare particle agglomerates and dust holding properties of the charged and discharged filter media.
Particle agglomerates on electret fiber surfaces grew with a dendritic structure. Agglomerates on the discharged media of the same physical properties displayed a more dense, collapsed structure. The discharged filter media was also found to be proportionally more heavily loaded with particles on the upstream side of the filter, resulting in less dust holding capacity (DHC). After filter loading to a final flow resistance of 5x the original clean filter resistance, the charged media was found to contain approximately 10% more dust than the discharged media. This study shows that the structure of dust deposits within filter media is influenced by filter properties and impacts the DHC of a filter. These microscale changes in agglomerate growth within the filter media produces a macroscale impact on the energy consumption of the filtration system, by changing the flow resistance through the filter life.