Browsing by Author "Chang, De-Qiang"

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Development of composite filters with high efficiency, low pressure drop, and high holding capacity PM2.5 filtration
(2019-04-01)
Chang, De-Qiang
;
Tien, Chi-Yu
;
Peng, Chien-Yuan
;
Tang, Min
;
Chen, Sheng-Chieh
Many efforts are being made to develop filters with high efficiency and high holding capacity but remaining a low pressure drop. A two-layer composite filter to achieve the goal was developed, in which the first layer was a charged coarse fibers to provide large void space for particle loading and the second was a thin layer of charged melt-blown with finer fibers to enhance the overall efficiency. Experimental results showed that although the new composite media had a lower initial efficiency than the other two HEPA filters (PTFE and glass fiber filter), its figure of merit (FOM) was the highest. Besides, the composite media had a better holding capacity for PM2.5 than the other two. At a fixed mass load, i.e., 2 g m(-2), the PTFE (Delta P = 380 Pa) and glass fiber (Delta P = 165 Pa) required around 7.6 and 3.3 times more power, respectively, than the composite media (Delta P = 50 Pa). Due to the low charge level of the coarse fiber layer and the fine fiber diameter of the melt-blown layer, resulted in no efficiency reduction along the loading process. Theoretical analysis showed that the charge shielding and the loss of efficiency in the successive top-down layers were timely compensated by the efficiency enhancement caused by the loading effects, which made the composite media a much uniform deposition of PM2.5 in layers. This was the main reason resulting in the high holding capacity and low pressure drop of the current composite media which acted like a perfect depth filtration media.
Removal Efficiency of Bimodal PM2.5 and PM10 by Electret Respirators and Mechanical Engine Intake Filters
(2016-07)
Chen, Sheng-Chieh
;
Chang, De-Qiang
;
Pei, Chenxing
;
Tsai, Chuen-Jinn
;
Pui, David Y. H.
As China is receiving an economic boom, PM (particulate matter) pollutions not only have become a serious regional problem but also frequently impacted its neighboring counties, e.g., Korea and Japan. In addition to its adverse effects on human health, the on-and off-road engines operated in ambient can also be affected. In this study, a simple system for generating simulated ambient bimodal PMs comprising fine (PM2.5), coarse (PM2.5-10) particles was developed for evaluating the initial efficiency of seven respirator and four engine intake filters. In addition to the size fractional efficiency curves for each filter media determined from the SMPS (scanning mobility particle sizer) and APS (aerodynamic particle sizer), both number and mass based efficiency of these filters for PM2.5, PM2.5-10 and PM10 were also obtained to evaluate their performances against ambient PM pollutions. Data showed that the engine intake filters had a low efficiency for both mass and number based PM2.5, which was only about 25-30%. However, there was a large difference between their number and mass based PM10 efficiency. The former was much lower than the latter because these filters are with high efficiency only for coarse particles. Besides, the most of particles in number was resided in the fine size range while the mass was in coarse size range. For the respirator filtration tests, results showed that most of them can effectively remove both PM2.5 and PM10, in which the mass efficiency was always higher than that of number. The PM2.5 number efficiency results showed there are three out of seven respirator filters are with N-95 rated level, in which the efficiency of their most penetrating particle size is higher than 95%. The current simple experimental system could be applied to examine different purpose filters which protect human health and outdoor engines against ambient PM2.5 and PM10.