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

Abstract

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.

Submicrometer particle removal indoors by a novel electrostatic precipitator with high clean air delivery rate, low ozone emissions, and carbon fiber ionizer

“…() was only 20% for 100‐ to 300‐nm particles at the relatively low air velocity of 0.4 m/s, whereas the air cleaner developed by Noh et al. () had an efficiency of 80% at 0.8 m/s. In the latter case, particle removal was enhanced by an electret filter, but the collection efficiency of the electret filter was only 60%, even when using four carbon fiber ionizers.…”

“…() and Noh et al. () also developed air cleaners using fibrous and electret filters, which were electrostatically assisted by carbon fiber ionizers. The particle removal efficiency of the air cleaner developed by Park et al.…”

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

“…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.…”

“…Introducing an ionizer in an electret filter system overcomes this drawback of the electret filter by supplying additional charges (Noh et al, 2011). 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. Therefore, the addition of ionizers did not help to increase collection efficiency because of the ion concentration limit of around 1 × 10 7 cm -3 (Noh et al, 2011). On the contrary, a corona discharge can produce unipolar ions with a high enough concentration.…”