Removal of PM2.5 entering through the ventilation duct in an automobile using a carbon fiber ionizer-assisted cabin air filter

This study was conducted to investigate the performance of a high-efficiency Heating, Ventilation and Air Conditioning (HVAC) filter and a top-of-the line Automotive Cabin Air (ACA) filter challenged with particles generated by the combustion of paper, wood, and plastic as well as with NaCl particles. The collection of submicron particles was examined under conditions representing two typical indoor air flow rates for the HVAC filter and two cabin fan control levels for the ACA filter. For the HVAC filter, almost all the collection efficiency values exceeded 80%; for the ACA filter, the collect efficiencies were much lower (< 40%) for all the tested aerosols and flow rates. Both filters demonstrated lower collection efficiency for combustion aerosols as compared to NaCl. This finding was consistent for all tested particle sizes and flow rates. The difference was always statistically significant in terms of the total efficiency (combining all sizes); however, the size-specific analysis of the differences revealed that the significance level varied with the particle size and flow rate. When tested under their operational flow conditions, the HVAC filter showed significantly better performance than the ACA filter. It was concluded that the filter performance characteristics of the HVAC and ACA filters obtained using wellestablished salt aerosol challenges may not accurately predict the performance of these filters against combustion aerosol particles. The difference was attributed to the interactions between the particles and filter fibers.

Section: Particle Size Specific Collection Efficiencysupporting

confidence: 71%

Section: Test Filtersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Performance of Electret Filters for Use in a Heating, Ventilation and Air Conditioning System and an Automotive Cabin against Combustion and NaCl Particles

Kim

Gao

Yermakov

et al. 2016

“…Previous studies that used an ionizer showed that the particle removal efficiency was improved from ~60% to 85% (Park et al, 2010;Noh et al, 2011). The efficiency could not be increased further, however, because of the upper limit of the unipolar ion concentration caused by mutual repulsion loss.…”

Section: Introductionmentioning

confidence: 94%

Capture of Ultrafine Particles Using a Film-Type Electret Filter with a Unipolar Charger

Sambudi

Choi

Lee

et al. 2017

Electret filters have been used widely to collect particles because of their low pressure drop and high collection efficiency due to the electrostatic attraction between the particles and filter. However, the collection efficiency of these filters decreases over time due to charge degradation. Therefore, a unipolar charger using a corona discharge was combined with an electret filter to overcome this decrease. The highest particle collection efficiency for 70 nm, uncharged particles occurred with a fresh electret filter was 34.0%, whereas a neutralized filter had a collection efficiency of 32.6%. However, when fresh and neutralized electret filters were used with a unipolar charger (electret field: 1.9 kV cm -1 ), the highest particle collection efficiencies of 99.8% and 98.2%, respectively, were obtained and appeared at the electrode-tomesh distance, a distance similar to the duct diameter. The distance between the tip of the discharge electrode and filter, which can be predicted using Sigmond's law, affected the charge density value on the filter surface. The ozone concentration was negligible under optimum conditions for particle collection. Therefore, using an electret filter combined with a corona discharge has good potential for improving air purifiers.

“…Huang et al (2008) examined the effect of ion-induced enhancement on the filtration of an HVAC filter with biological aerosols, including aerosolized bacterial cells, bacterial and fungal spores, and viruses. Park et al (2010) reported the effect of a carbon fiber ionizer-assisted cabin air filter on PM 2.5 reduction. They showed that a carbon fiber ionizer installed in front of an electret cabin air filter increased the PM 2.5 reduction by 20-21%.…”

Section: Introductionmentioning

confidence: 99%

Filtration of Submicron Aerosol Particles Using a Carbon Fiber Ionizer-assisted Electret Filter

Noh

Lee

Kim

et al. 2011

Self Cite

The effects of a carbon fiber ionizer on the collection efficiency of an electret filter for residential house ventilation were investigated with varying the face velocity, the number of ionizers, and the polarity of the ionizer. A Flimmer filter, which was made by a Swedish company, was used as the electret filter. The air ion concentration upstream of the filter gradually increased as the velocity increased. Under the same conditions of velocity and the same number of ionizers, the positive ion concentrations were slightly higher than the negative ones. The ion concentration at any location away from the ion source was only slightly affected by the number of ionizers. When ionizers were used in front of the Flimmer filter, the collection efficiencies for submicron particles increased by 10 to 25%. When positive ionizers were used, the collection efficiencies were 10 to 15% higher than with the negative ionizers. The increase in collection efficiency occurred because most of the generated air ions were captured on the surface of the electret filter fibers, thereby increasing the electrostatic potential inside the electret filter.