• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.315-323
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• 2004

An electrical cascade impactor is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. A Faraday cage and an aerosol charger, which are basic components of the electrical cascade impactor, were designed and evaluated in this study. The low-level current response of the Faraday cage was investigated with changing particle size and air flow rate by using sodium chloride (NaCl) particles. The response of the prototype Faraday cage was very similar to that of a commercial aerosol electrometer (TSI model 3068) within ${\pm}$5% for singly-charged particles. The response linearity of the prototype Faraday cage could be extended up to flow rate of 30 L/min. For the performance evaluation of the aerosol charger the monodisperse liquid dioctyl sebacate (DOS) particles, with diameters of 0.1∼0.8$\mu\textrm{m}$, were generated using spraying from an atomizer followed by evaporation-condensation process. Typical performance parameters of the aerosol charger such as P$.$n, wall loss, and elementary charges per particle were evaluated. The performance of the prototype aerosol charger was found to be close to that of the aerosol charger used in an electrical low pressure impactor (ELPI, Dekati).

• Particle and aerosol research
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• v.13 no.4
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• pp.151-158
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• 2017

Electrostatic precipitator is widely used to remove particulate matters in indoor air and industrial flue gas due to low pressure drop and high collection efficiency. However, it has a low collection efficiency for the submicrometer sized particles. Electrospraying is a potential method to increase the particle charging efficiency, which results in increased collection efficiency. Although particle charging efficiency is highly dependent upon droplet size, the effective measuring method of the droplets is still uncertain. Tap water was electrosprayed in this study, and the images of electrosprayed droplets were taken with a high speed camera coupled with several visualization methods in order to measure the droplets size. The droplet size distribution was determined by an image processing with an image-J program. As a result, a droplet measured by a laser visualization, had a half size of that by a Xenon light visualization. In addition, the experimentally measured droplet sizes were a good agreement with the predicted values suggested by $Fern{\acute{a}}ndez$ de la Mora and Loscertales(1994).

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.229-235
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• 2002

The apparent volume resistivity of powders measured by both the tapping and the compressing methods was compared in this study. Factors such as applied voltage, pressure, corona charging, and so on affecting the apparent volume resistivity of polymer powders were also examined experimentally. Powders of polyacrylonitrile and Nylon 11 were mainly used. The values of the apparent resistivity of polymer powders taken by the tapping method turned out to be larger than those taken by the compressing method, which indicates that the apparent volume resistivity of polymer powders depends strongly on the measurement method. The apparent resistivity of polymer powders increased with an increase in applied voltage while it decreased with an increase in pressure, tapping time, and particle size. The influence of the moisture content of powder and corona charging on the resistivity of polymer powders is also discussed.

• Particle and aerosol research
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• v.9 no.2
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• pp.39-50
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• 2013

Real-time aerosol measuring instruments have been widely used for the measurement of atmospheric aerosol, diesel particulate matter, or material synthesis. A scanning mobility particle sizer (SMPS) measures the number size distribution of particles using electrical mobility detection technique. An aerodynamic particle sizer (APS) is used to determine the number concentration and the mean aerodynamic diameter of test particles. An electrical low-pressure impactor (ELPI) is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. In this study, the performance of these instruments were evaluated to assess their ability to obtain mass concentrations from particle number concentration measurements made as a function of particle size. The effect of determination of particle density on the measurement of mass concentration was investigated for the three instruments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.171-176
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• 2018

An electronic paper display was fabricated by injecting electronic ink, including white and black particles coated by positive and negative charge control agents (CCA), respectively, into closed cells surrounded by micro-barriers. These two types of charged, colored particles are easily damaged or their charging value can be changed by the injection process; therefore, the electrical and optical properties of the image panel fabricated by the injection method were estimated in this study. The active particle-loading method, proposed as a new electronic ink injection process, was applied, and the electro-optical properties of the resulting three-electrode-type e-paper image panel were analyzed. The reflection rate of the white image-panel fabricated with our new injection method was 24.7%, while that of the same panel fabricated with a previously reported injection method was 19.8%. In addition, the response time was improved by about five times compared to those reported in other publications.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.804-812
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• 2001

A triboelectrostatic separation system for removing unburned carbon from coal fly ash is designed and evaluated. Fly ash from a coal-fired power plant is used as an accepted additive in concrete where it adds strength, sulfate resistance and reduced cost, provided acceptable levels of unburned carbon are maintained. Unfortunately, unburned carbon in coal fly ash absorbs some of other additives and reduces the concrete strength. This paper describes to investigate dry triboelectrostatic process to separate unburned carbon from coal fly ash and utilize it into economically valuable products. The laboratory-scale triboelectrostatic separation system consists of a particle feeding system, a tribocharger, a separation chamber, and collection systems. Particles of unburned carbon and fly ash can be imparted positive and negative surface charges, respectively, with a copper tribocharger due to differences in the work function values of the particles and the tribocharger, and can be separated by passing them through an external electric field. Results showed that fly ash recovery was strongly dependent on the electric field strength and the particle size. 70wt% of fly ash containing 6.5wt% of carbon contents could be recovered at carbon contents below 3%. The triboelectrostatic separation system showed a potential to be an effective method for removing unburned carbon from coal fly ash.

• Journal of Astronomy and Space Sciences
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• v.35 no.3
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• pp.175-183
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• 2018

Many recent satellites have mission periods longer than 10 years; thus, satellite-based local space weather monitoring is becoming more important than ever. This article describes the instruments and data applications of the Korea Space wEather Monitor (KSEM), which is a space weather payload of the GeoKompsat-2A (GK-2A) geostationary satellite. The KSEM payload consists of energetic particle detectors, magnetometers, and a satellite charging monitor. KSEM will provide accurate measurements of the energetic particle flux and three-axis magnetic field, which are the most essential elements of space weather events, and use sensors and external data such as GOES and DSCOVR to provide five essential space weather products. The longitude of GK-2A is $128.2^{\circ}E$, while those of the GOES satellite series are $75^{\circ}W$ and $135^{\circ}W$. Multi-satellite measurements of a wide distribution of geostationary equatorial orbits by KSEM/GK-2A and other satellites will enable the development, improvement, and verification of new space weather forecasting models. KSEM employs a service-oriented magnetometer designed by ESA to reduce magnetic noise from the satellite in real time with a very short boom (1 m), which demonstrates that a satellite-based magnetometer can be made simpler and more convenient without losing any performance.

• Particle and aerosol research
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• v.13 no.1
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• pp.11-16
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• 2017

Indoor air quality is of increasing concern because it is closely related human health. An air handling unit (AHU) can be used to control the indoor air quality related to particulate matters and $CO_2$ as well as air conditioning such as temperature and humidity of indoor air. An electrostatic precipitator has a high collection efficiency and low pressure drop, however, ozone can possibly generate from its chargers, which is one of drawbacks to apply it for indoor air control. Here we compared four charging electrodes such as a $50{\mu}m$ tungsten wire, a $100{\mu}m$ tungsten wire, a $16{\mu}m$-thickness Al foil and a carbon fabric comprised of $5-10{\mu}m$ fibers. The carbon fabric electrode showed a superior particle collection efficiency and a lower ozone generation at a given power consumption compared to tungsten wires of 50, $100{\mu}m$ and an Al foil electrode. This low ozone generating, micro-sized electrode can be applied to the electrostatic precipitator in AHU for indoor air control.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.97-105
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• 1998

The goal of this study is to investigate the potential application of triboelectrostatic separation process for removing unburned carbon from fly ash. The process utilizes the difference in electrical charging characteristics between the organic material (carbon) and the mineral matter (fly ash). In the present work, dry separation tests have been conducted on Samchunpo fly ash samples using a bench - scale analytic separator. The test variables studied include air rate, feed rate, electric field strength, particle size, charger material and length, etc. The best separation results were obtained at the air rate 501/min, feed rate 15 g/min and voltage 15 ㎸. The fly ash with carbon content below 1 % was obtained with over 65% recovery.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2021-2030
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• 2017

In this paper, the unipolar corona-needle charger was developed and its capabilities were both numerically and experimentally investigated. The experimental corona discharges and particle losses in the charger were obtained at different corona voltage, aerosol flow rate and particle diameter for positive and negative coronas. Inside the charger, the electric field and charge distribution and the transport behavior of the charged particle were predicted by a numerical simulation. The experimental results yielded the highest ion number concentrations of about $1.087{\times}10^{15}ions/m^3$ for a positive corona voltage of about 3.2 kV, and $1.247{\times}10^{16}ions/m^3$ for a negative corona voltage of about 2.9 kV, and the highest $N_it$ product for positive and negative coronas was found to about $7.53{\times}10^{13}$ and $8.65{\times}10^{14}ions/m^3$ s was occurred at the positive and negative corona voltages of about 3.2 and 2.9 kV, respectively, and the flow rate of 0.3 L/min. The highest diffusion loss was found to occur at particles with diameter of 30 nm to be about 62.50 and 19.33 % for the aerosol flow rate of 0.3 and 1.5 L/min, respectively, and the highest electrostatic loss was found to occur at particles with diameters of 75 and 50 nm to be about 86.29 and 72.92 % for positive and negative corona voltages of about 2.9 and 2.5 kV, respectively. The numerical results for the electric field distribution and the charged particles migration inside the charger were used to guide the description of the electric field and the behavior of charged particle trajectories to improve the design and refinement of a unipolar corona-needle charger that otherwise could not be seen from the experimental data.