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- Shi, Bingbing, 1983, et al.
(författare)
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Influence of Filter Fiber Material on Removal of Ultrafine and Submicron Particles Using Carbon Fiber Ionizer-Assisted Intermediate Air Filters
- 2012
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Ingår i: ASHRAE Transactions. - 0001-2505. ; 118:PART 1, s. 602-611
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Konferensbidrag (refereegranskat)abstract
- Ultrafine and submicron particles are possibly highly related with respiratory and cardiopulmonary diseases and syndromes. Many studies show that an ionizer operated upstream of a ventilation air filter could enhance the particle collection efficiency of the filter, without affecting the pressure drop. However, most of these studies are based on one single fiber material and does not develop any comparison among different ventilation filters. This study investigates the influence of the fiber material and filter class on the enhanced efficiency. The influence of ion concentration is also considered. The experiments were conducted in a full-scale filter test rig and a chamber with 100% air re-circulation. Seven ventilation filters of class F5-F9 (MERV11-15), made of three types of fiber materials were tested in the filter test rig. A Scanning Mobility Particle Sizer (SMPS) was utilized to count ultrafine and submicron particles in the upstream and downstream air flow. In the chamber test, a charged synthetic filter of class G4 (MERV 8) was mounted in the air re-circulation system. A P-TRAK Ultrafine Particle Counter, a CI-500 optical particle counter and a Dust-TRAK Aerosol Monitor were used to measure ultrafine and submicron particles. The results show, under the given experimental conditions, that ionization could substantially improve the filtration efficiency. For example, assisted by the ionizer, the coarse G4 (MERV 8) filter showed a filtration efficiency that increased by about 30 to 40 %-units for submicron particles. For the same ion concentration, the enhanced efficiency of charged synthetic filters is higher than that of glass fiber filters, especially in the ultrafine particle size fraction. Similarly, with the same ion concentration, the charged synthetic filters of higher class showed higher enhanced efficiencies than the charged synthetic filters of lower class. Measurements showed a negligible generation of ozone, both in the filter test rig and in the test chamber experiments.
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| 2. |
- Shi, Bingbing, 1983
(författare)
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Removal of ultrafine particles by intermediate air filters in ventilation systems. Evaluation of performance and analysis of applications.
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epidemiological and toxicological studies demonstrate that ultrafine particles (UFPs) are strongly related with respiratory and cardiovascular diseases and syndromes. One common method to reduce human exposure to particulate air pollution is the use of intermediate class filters (F5-F9 class filters according to EN779:2002). However, the efficiency of such filters, with respect to UFPs, is not well explored. Furthermore, neither the European standard nor the US standard for classification of intermediate class filters comprises performance with respect to UFPs or particles of the most penetrating size (MPPS). This could turn out to be a major lack in classification standards since UFPs have been pointed out as a potential serious health hazard. To fill in the gap, the purpose of the thesis is to evaluate the performance of intermediate class filters available on the Swedish market, and to correlate the efficiency for UFPs (EFUFP) and MPPS-size particles (EFMPPS) with the EN779 classification efficiency for particles of the size 0.4μm (EF0.4μm). The thesis also contains analyses of 1) air filtration for indoor particles of outdoor and indoor origin; 2) how to efficiently apply intermediate air filters in two-step air filtration systems and 3) ionizer assisted air filtration.Size-resolved filtration efficiencies of 23 filter sheets and 8 full-scale filters were tested in laboratory experiments with four types of upstream aerosols. The relationships between EFUFPs, EFMPPS and EF0.4μm were investigated under different testing conditions. The results showed that the electrostatic force from charged filter fibers has big influence on the shape of the efficiency curves. Additionally, the electrical charge state of the upstream aerosol is critical for the testing of charged synthetic filters. Linear relationships were found between EFUFPs, EFMPPS and EF0.4μm within the observed efficiency range for both glass fiber and charged synthetic filters. In general, EFMPPS was 10-20%-units lower than EF0.4μm. The values of EFUFPs were close to EF0.4μm for glass fiber filters, while EFUFPs were lower than EF0.4μm for charged synthetic filters. Theoretical analysis showed that filter operating hours and classes are critical to the cost of two-step filtration, i.e. a solution where a pre-filter protects the main filter. Under suitable operation, two-step filtration is not necessarily more expensive than single-step filtration. Another analysis investigated suitable filter class, filtration locations, and the ratio of supply to outdoor air flow rate, for efficient removal of particles coming from indoor and outdoor sources. The results can be used to recommend suitable air filters and ventilation rates/modes or to predict the existing system performances. Yet a separate study, based on measurements, shows that an F7 class filter assisted with an ionizer may reach an efficiency similar to that of a single F9 class filter.
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