This study was undertaken to determine the effects of using an electret filter on aerosol penetration. Various factors, including particle size (0.05 to 0.5 micro m), aerosol charge state (neutral and single charge), face velocity (0.1, 0.3, 0.5 and 1.0 m/s), and relative humidity (RH 30% and RH 70%), were examined to assess their effects on aerosol collection characteristics. The results presented here demonstrate that the electric fields of the electret and discharged filter were -1.53 x 104 and -1.3 x 102 (V/m). The penetration through the electret filter with singly charged aerosol and neutral aerosol ranged from 0.4% to 13% and 14% to 29%, respectively. According to these results, the coulombic capture force was dominant for the smaller aerosol and the dielectrophoretic capture mechanism was considered important for the larger aerosol. The level of penetration through the electret filter increased with increasing face velocity and relative humidity. The temperature did not affect the penetration through the electret. Furthermore, from the regression analysis conducted during the operating conditions of this work, the aerosol charge was shown to exert the greatest influence on aerosol penetration.
Heating, ventilating, and air-conditioning (HVAC) systems ensure indoor air quality and provide a comfortable environment. However, the conventional HVAC systems only provide indoor ventilation and adjust temperature and humidity. This work removes indoor volatile organic compounds (VOCs) using a feasible and novel air-cleaning for an HVAC system, to remove indoor VOCs. An activated carbon-fiber (ACF) filter calcined with copper oxide (CuO) catalyst, called a CuO/ACF catalyst filter, was the developed kit. Formaldehyde, a major VOC, was chosen as the target pollutant. Experiments were performed to confirm the filtration ability of the CuO/ACF catalyst filter in removing formaldehyde in a stainless-steel chamber equipped with a simplified HVAC system. Total air exchange rate (ACH) was controlled at 0.5 and 1.0 h À1 , the fresh ACH was 0.15 and 0.30 h À1 , and relative humidity (RH) was set at 30 and 70%. A first-order decay of formaldehyde existed in the controlled chamber when the two pretreated CuO/ACF catalyst filters were employed. Experimental results demonstrate that the CuO/ACF catalyst filters removed formaldehyde effectively. The decay constant was 0.425 and 0.618 h À1 for 0.5 and 2.0 ppm formaldehyde, respectively. Moreover, the formaldehyde decay rate increased as total ACH, fresh ACH, RH, and the Cu(NO 3 ) 2 concentration for calcination of CuO/ACF catalyst filter increased.
Fine aerosols with a diameter of less than 2.5 microns (PM2.5) have a significant negative impact on human health. However, their measurement devices or instruments are usually expensive and complicated operations are required, so a simple and effective way for measuring the PM2.5 concentration is needed. To relieve this problem, this paper attempts to provide an easy alternative approach to PM2.5 concentration estimation. The proposed approach is based on image processing schemes and a simple linear regression model. It uses images with a high and low PM2.5 concentration to obtain the difference between these images. The difference is applied to find the region with the greatest impact. The approach is described in two stages. First, a series of image processing schemes are employed to automatically select the region of interest (RoI) for PM2.5 concentration estimation. Through the selected RoI, a single feature is obtained. Second, by employing the single feature, a simple linear regression model is used and applied to PM2.5 concentration estimation. The proposed approach is verified by the real-world open data released by Taiwan’s government. The proposed scheme is not expected to replace component analysis using physical or chemical techniques. We have tried to provide a cheaper and easier way to conduct PM2.5 estimation with an acceptable performance more efficiently. To achieve this, further work will be conducted and is summarized at the end of this paper.
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