• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.97-103
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• 2001

The effects of the electrohydrodynamic (EHD) flow and turbulent diffusion on the collection efficiency of a model ESP composed of the plates with a cavity were studied through numerical computation. The electric field and ion space charge density were calculated by the Poisson equation of the electrical potential and the current continuity equation. The EHD flow field was solved by the continuity and momentum equations of the gas phase including the electrical body force induced by the movement of ions under the electric field. The RNG $k-{\varepsilon}$ model was used to analyze the turbulent flow. The particle concentration distribution was calculated from the convective diffusion equation of the particle phase. As the ion space charge increased, the particulate collection efficiency increased because the electrical potential increased over the entire domain in the ESP. The collection efficiency decreased and then increased, i.e. had a minimum value, as the EHD circulating flow became stronger when the electrical migration velocity of the charged particle was low. However, the collection efficiency decreased with the stronger EHD flow when the electrical migration of the particle was higher relatively. The collection efficiency of the model ESP increased as the turbulent diffusivity of the particle increased when the electrical migration velocity of the particle was low. However, the collection efficiency decreased for increasing the turbulent diffusivity when the electrical migration of the particle was higher relatively.

• 한국대기환경학회지
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• 제9권2호
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• pp.125-131
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• 1993

Electrostatic Precipitator has been widely used to get high efficiency which is required for collection of fine particles. In order to provide collection efficiency and size distribution data for a pilot electrostatic precipitator, a pilot study has been conducted on fly ash from pulverized coal burning apparatus. The aims of this study are to investigate characteristics of electric charge, to measure collection efficiency varied with the applied voltage, to get an optimum current and current density. Optimum current density was obtained to 0.7mA/$cm^2$ at the average electric field strength 2.33kV/cm in this experiment. Maximum particle collection efficiency was indicated 99.21% at the applied voltage 7kV. Finally, particle size distribution is also compared with photographic results. Both coarse and fine particles at the range of 0.5$\sim$2$\mu$m and 3$\sim$10 SEM $\mu$m were clearly removed by increasing applied voltage.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.466.2-466.2
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• 2014

The Quantum dot (QD) solar cells have been under active research due to their high light harvesting efficiencies and low fabrication cost. In spite of these advantages, there have been some problems on the charge collection due to the limitation of the diffusion length. The modification of advanced nanostructure is capable of solving the charge collection problem by increasing diffusion length of electron. One dimensional nanomaterials such as nanorods, nanowires, and nanotubes may enhance charge collection efficiency in QD solar cells. In this study, we synthesized $TiO_2$ anatase nanorod arrays with length of 200 nm by two-step sol-gel method. The morphology and crystal structure for the nanorod were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The anatase nanorods are single-crystalline and possess preferred orientation along with (001) direction. The photovoltaic properties for the heterojunction structure QD solar cells based on the anatase nanorod were also characterized. Compared with conventional $TiO_2$ nanoparticle based QD solar cells, these nanostructure solar cells exhibited better charge collection properties due to long life time measured by transient open circuit studies. Our findings demonstrate that the single crystalline anatase nanorod arrays are promising charge transport semiconductors for heterojunction QD solar cells.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.85-90
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• 2001

This work presents experimental results of filter media test by using particles from $0.02\;to\;0.6{\mu}m$ in diameter and by applying different charging states. In order to investigate the electret filter performance, the collection efficiency and the pressure drop of filter were measured. The face velocities of test filters varied from 2.4 to 20.4 cm/s. Another experiment setup for the cartridge cabin air filter was used to get an collection efficiency in submicron region. After charging level of electret filter severely decreased, the change of collection efficiency was verified. Experimental results show that the reliability of electret filters can be poor in some conditions.

• 한국정밀공학회지
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• 제14권1호
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• pp.84-89
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• 1997

Recentely, a compact and small size air-cleaning Electrostatic Precipitator(ESP) is needed to develop for air conditioning devices. From Deutsch formula for ESP efficiency, collection efficiency is affected not only the structure of collection section but also the charge rate of dust. In terms of collection area, the most useful type is a scroll type ESP. In this work, we investigated experimentally aptimum design factor of scroll type ESP by application of Taguchi method. And we developed the scroll type ESP by using optimal condition of control factor.

• 한국입자에어로졸학회지
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• 제19권3호
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• pp.89-100
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• 2023

In our previous study, a wire-plate type electrostatic precipitator (ESP) was developed to collect bioaerosols of 100 nm size. In the study, various flow rates (40 ~ 100 L/min) and applied voltages (3 ~ 10 kV) were tested for experiment. In this study, numerical analysis was performed for the ESP of the previous study with the same flow rates and applied voltages, but with varying the size of bioaerosols to 0.04 ~ 2.5 ㎛. Overall, the numerical analysis results well predicted the experimental data. Bioaerosols of 0.1 ~ 0.5 ㎛ showed the minimum collection efficiency for all conditions because of low charge number. The effect of the ionic wind generated by the corona discharge was calculated. However, the ionic wind did not affect much the collection efficiency. The aerosol collection in the ESP of this study was due to the electrostatic force generated by particle charge in the electric field. This numerical study on the ESP can be used for the design and optimization of higher flow rate (> 100 L/min) ESP.

• Journal of Radiation Protection and Research
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• 제30권2호
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• pp.69-75
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• 2005

기체전자증폭기(GEM, gas electron multiplier)는 동박이 양면으로 도포된 절연기관에 미세구멍배열을 형성한 박막으로 기존의 기체형 방사선 검출기의 미약한 방사선 신호를 증폭하기 위해 널리 사용되어지고 있다. 미세구멍 내부에 강한 전기장을 형성함으로써 이 내부로 유입되는 전자에 충분한 에너지를 전달, 전자사태를 유도하는 원리를 이용한다. 따라서 GEM의 특성은 GEM을 포함한 방사선 검출기에 인가되는 전압 즉, 전기장의 분포에 의해 결정된다. 따라서 올바르지 못한 전기장의 분포에 대해서는 신호 전자가 수집전극으로 향하지 못하고, GEM의 상 하단의 전극으로 이동, 신호의 손실을 초래할 수도 있다. 본 논문에서는 GEM의 가장 중요한 성능 지표 중 하나인 1차 전자수집효율(primary electron collection efficiency)을 계산하였다. 방사선에 의해 발생된 전자는 전기력선을 따라서만 움직인다는 가정 하에, GEM의 단위 구조에 대해 표류전극에서의 전기력선의 수에 대한 수집전극에서의 전기력선의 수의 비로 전자수집효율을 계산하였다. 전기력선의 계산은 3차원 유한요소법을 이용하여 계산하였다. 본 논문에서 사용한 방법은 가장 이상적인 상황으로 국한되지만, GEM의 설계 및 최적 운전변수 도출에 유용하게 사용될 수 있을 것이다.

• 한국대기환경학회지
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• 제21권2호
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• pp.145-153
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• 2005

An electret fiber with a dipole charge distribution was used to capture charged ultrafine particles in this study. Brownian diffusion and Coulombic force are the dominant collection mechanisms in the electret filtration of charged ultrafine particles. The interaction between Brownian diffusion and Coulombic force for the deposition of ultrafine particles onto a dipolarly charged fiber is studied by solving the convective diffusion equation including Coulombic force as an external force, and the numerical results are compared with the experimental data. As a result, it is shown that there is a negative interaction between Brownian diffusion and Coulombic force, i.e., Coulombic capture efficiency is reduced with decreasing Pe. These results suggest that Brownian diffusion and Coulombic capture efficiency, $\eta$$_{CD}$ is not a simple sum of Brownian diffusion efficiency, $\eta$$_{D}$ and Coulombic capture efficiency, $\eta$$_{C}$.

• 대한환경공학회지
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• 제33권8호
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• pp.598-605
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• 2011

본 연구의 주 목적은 다층 다단 다공성 시스템에 편극전하 방식을 부가하여 본 시스템의 집진특성을 실험적으로 해석하는데 있다. 본 시스템의 압력손실 및 집진효율 특성 해석을 위해 실험은 인가전압, 시스템 유입유속, 유입농도 및 stage 수 등의 실험적 변수들에 의해 수행된다. 실험결과, 기류유입 시 유입유속 $v_{in}$ = 3.11 m/s에서 단(stage) 수 변화($1{\rightarrow}5$단)에 따라 압력손실은 $18{\sim}134mmH_2O$를 나타낸다. 인가전압 0 kV 및 기류유입이 없을 때, 시스템 유입유속 $v_{in}$ = 2.58 m/s인 경우 5 stage에서 집진효율은 92.5% 인 데 비해, 동일 유속에서 플레이트 별 편극전하(alternating polarization charge-applied voltage 2.5 kV) 및 기류유입 시스템인 경우 5 stage 효율은 98.5%로 전자에 비해 6% 정도 매우 높은 효율 상승을 보인다.

• Journal of Electrochemical Science and Technology
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• 제1권2호
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• pp.69-74
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• 2010

Methodologies to improve photovoltaic performance of dye-sensitized solar cell (DSSC) are reviewed. DSSC is usually composed of a dye-adsorbed $TiO_2$ photoanode, a tri-iodide/iodide redox electrolyte and a Pt counter electrode. Among the photovoltaic parameters of short-circuit photocurrent density, open-circuit voltage and fill factor, short-circuit photocurrent density is the collective measure of light harvesting, charge separation and charge collection efficiencies. Internal quantum efficiency is known to reach almost 100%, which indicates that charge separation occurs without loss by recombination. Thus, light harvesting efficiency plays an important role in improvement of photocurrent. In this paper, technologies to improve light harvesting efficiency, including surface area improvement by nano-dispersion, size-dependent light scattering efficiency, bi-functional nano material, panchromatic absorption by selective positioning of three different dyes and transparent conductive oxide (TCO)-less DSSC, are introduced.