에어로졸 중화기의 나노 입자 하전 특성

지준호,배귀남,황정호,Ji, Jun-Ho,Bae, Swi-Nam,Hwang, Jung-Ho 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.10

Aerosol charge neutralizers with various radioactive sources have been used to apply an equilibrium charge distribution to aerosols of unknown charge distribution. However, the performance of aerosol charge neutralizers is not well known, especially for highly charged particles. Measurements of highly charged particles are needed in air cleaning devices, e.g. electrostatic precipitator, bag filter with a pre-charger, and electrical cyclone. In this study, the particle charging characteristics of two different aerosol charge neutralizers were experimentally investigated for singly charged monodisperse particles and highly charged polydisperse particles. One has radioactive source of $^{85}$ Kr (beta source, 2 mCi) and the other has $^{210}$ Po (alpha source, 0,5 mCi). The air flow rate passing through each aerosol charge neutralizer was changed from 0.2 to 2.5 L/min. The results show that the charge distribution of singly charged monodisperse particles passing through the $^{85}$ Kr aerosol charge neutralizer is well agreed with the Boltzmann equilibrium charge distribution at an air flow rate of 0.3 L/min, However, it deviates from the equilibrium charge distribution when the air flow rates are 0.6, 1,0, and 1,5 L/min, On the other hands, the effect of air flow rate is insignificant for the $^{210}$ Po aerosol charge neutralizer. The non-equilibrium character in charge distribution of highly charged polydisperse particles passing through the $^{85}$ Kr aerosol charge neutralizer greatly depends on the air flow rate, however it is insensitive to the air flow rate for the $^{210}$ Po aerosol charge neutralizer.

전기가열 튜브로를 이용한 나노/서브마이크론 입자의 발생

지준호,배양일,황정호,배귀남,Ji, Jun-Ho,Pae, Yang-Il,Hwang, Jung-Ho,Bae, Gwi-Nam 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.12

Aerosol generator using an electrically heated tube furnace is a stable apparatus to supply nanometer sized aerosols by using the evaporation and condensation processes. Using this method, we can generate highly concentrated polydisperse aerosols with relatively narrow size distribution. In this work, characteristics of particle size distribution, generated from a tube furnace, were experimentally investigated. We evaluated effects of several operation parameters on particle generation: temperature in the tube furnace, air flow rates through the tube, size of boat containing solid sodium chloride(NaCl). As the temperature increased, the geometric mean diameter increased and the total number concentration also increased. Dilution with air affected the size distribution of the particles due to coagulation. A smaller sized boat, which has small surface area to contact with air, brings smaller particles of narrow size distribution in comparison of that of a larger boat. Finally, we changed the electrical mobility diameter of aggregate sodium chloride particles by varying relative humidity of dilution air, and obtained non-aggregate sodium chloride particles, which are easy to generate exact monodisperse particles.

노즐 막힘이 미세 오리피스형 다단 임팩터의 입자 채취 성능에 미치는 영향

지준호,배귀남,황정호,Ji, Jun-Ho,Bae, Gwi-Nam,Hwang, Jung-Ho 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.2

A cascade impactor is a multistage impaction device used to separate airborne particles into aerodynamic size classes. A micro-orifice impactor uses micro-orifice nozzles to extend the cut sizes of the lower stages to as small as 0.05 ${\mu}{\textrm}{m}$ in diameter without resorting to low pressures or creating excessive pressure drops across the impactor stages. In this work, the phenomenon of particle clogging in micro-orifice nozzles was experimentally investigated for a commercial micro-orifice uniform deposit impactor (MOUDI). It was observed, using an optical microscope, that the micro-orifice nozzles of the final stages were partially clogged due to particle deposition during the aerosol sampling. Therefore the pressure drops across the nozzles were higher than the nominal values given by the manufacturer. To examine the effect of particle clogging in micro-orifice nozzles, the particle collection efficiency of the MOUDI was evaluated using an electrical method for fine particles with diameters in the range of 0.1-0.6 ${\mu}{\textrm}{m}$. The monodisperse liquid dioctyl sebacate (DOS) particles were used as test aerosols. A faraday cage was employed to measure the low-level current of the charged particles upstream and downstream of each stage. It was found that the collection efficiency curves shifted to correspond to smaller orifice sizes, and the 50-% cutoff sizes were much smaller than those given by the manufacturer for the three stages with nozzles less than 400 ${\mu}{\textrm}{m}$ in diameter.

입자 퇴적이 승용차용 정전 필터의 미세 입자 포집 특성에 미치는 영향

지준호,강석훈,황정호,배귀남,Ji, Jun-Ho,Gang, Seok-Hun,Hwang, Jeong-Ho,Bae, Gwi-Nam 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8

An electret filter is composed of permanently charged electret fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using poly-disperse particles when submicron particles were loaded. Long-term experiments were conducted by applying two different charging states, which were spray electrification and charge equilibrium by bipolar ionization. In order to investigate the effect of particle loading in filter media, NaCl particles were generated from 0.1% and 1% solutions by an atomizer. Liquid DOS particles were used to evaluate the effect of liquid particles on the collection efficiency of an electret filter. The results show significant effect of charge amount and size distribution of loading particles on the collection performance of a filter media in submicron region. Smaller particles loaded in electret fibers cause a more rapid degradation in collection efficiency and have lower minimum efficiency with time. The pressure drop of a filter media do rarely increase when the collection efficiency decreases to the minimum value. For the larger particles charged by spray electrification, which have charge amounts more than that of Boltzmann equilibrium charge distribution, the pressure drop of a filter media slowly increases in comparison with that of equilibrium charged particles. For DOS particles it is shown that the charging level of an electret filter severely decreases and the collection efficiency is below 10% in some particle size range.

승용차용 정전 필터의 미세 입자 포집 특성

지준호,강석훈,김동철,황정호,윤웅섭,배귀남,Ji, Jun-Ho,Gang, Seok-Hun,Kim, Dong-Cheol,Hwang, Jeong-Ho,Yun, Ung-Seop,Bae, Gwi-Nam 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.11

An electret filter is composed of permanently charged electret fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the fractional collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using highly monodisperse particles ranging from 0.02 to 0.6 $\mu\textrm{m}$ in diameter at three different charging states: singly charged, uncharged, and equilibrium charged. The face velocity was varied from 2.4 to 20.4 crus. It was fecund that the fractional efficiency curve fur singly charged particles shows a typical trend that the collection efficiency is minimum at about 0.3 $\mu\textrm{m}$ in diameter. The fractional efficiency of equilibrium charged particles were not severely varied with the particle diameter. The collection efficiency curve fur uncharged particles has a minimum near 0.1 $\mu\textrm{m}$ in diameter. Another experiment was conducted for a cartridge filter to examine the effect of charge depletion on the collection efficiency in a cabin air filter. The result shows that the charge depletion of the cartridge filter can significantly lower the collection efficiency.

나노물질과 나노제품, 그리고 상용화 문제

지준호,Ji, Jun-Ho 한국공기청정협회 2007 空氣淸淨技術 Vol.20 No.3

사무실의 실내 청소 과정에서 부유하는 미세먼지의 크기분포

지준호,Ji, Jun-Ho 한국입자에어로졸학회 2018 Particle and Aerosol Research Vol.14 No.2

본 연구에서는 청소 과정에서 바닥에 먼지가 실내 공기 중으로 비산되는 특성을 공기 중 미세먼지를 측정하여 분석하였다. 신발을 벗지 않고 생활하는 국내 사무실을 대상으로 하였고, 실내 청소 과정에서 발생하는 미세먼지를 측정하였다. 미세먼지($PM_{10}$)와 초미세먼지($PM_{2.5}$)와 $1{\mu}m$ 보다 작은 먼지의 무게농도($PM_{1.0}$)을 분석하였고, 청소 과정에서 발생하는 $0.3{\mu}m$ 이상의 먼지의 크기를 측정하여 분석하였다. 특히, 빗자루질과 진공청소기를 사용하는 과정에서 재비산 되는 미세먼지의 특성을 분석하였고, 입자의 크기에 따른 재비산 특성과 실내 농도 변화 특성을 확인하였다. $PM_{2.5}$와 $PM_{10}$은 청소 시작과 함께 농도가 증가하였고, 청소 이후에도 실내에 부유하여 장시간 인체에 노출될 수 있을 것으로 보인다. 반면에 $PM_{1.0}$은 상대적으로 청소과정에서 농도가 증가하는 경향을 확인할 수 없었다. 특히, $2.5{\sim}10{\mu}m$ 크기의 먼지는 바닥에 먼지가 많은 조건에서 빗자루질로 청소하는 경우, 초기 농도의 약 60배까지 높아질 수 있음을 확인하였다. 바닥에 먼지가 적은 조건에서 진공청소기를 사용하는 경우도 $2.5{\sim}10{\mu}m$ 크기의 먼지가 증가하였지만 초기 농도의 5배 이하였다. 중성능급 배기필터가 장착된 진공청소기가 가동하는 동안 CPC로 측정된 총 개수농도가 급격히 증가한 후 감소하는 특성이 나타났다. 개수로 대부분을 차지하는 먼지는 250 nm 보다 작은 크기였다. 실내 거주자의 미세먼지 노출은 외부에서 유입된 대기 미세먼지와 실내에서 발생된 실내 생성 미세먼지가 함께 영향을 준다고 알려져 있다. 그렇지만, 국내 실내 활동 중 발생되는 미세먼지에 대한 체계적인 측정과 분석 연구가 많지 않았다. 이미 진행되고 있는 다양한 대기 미세먼지 연구 뿐 아니라 앞으로는 실내의 다양한 활동에 기인한 미세먼지 생성 특성에 대한 심도 깊은 연구가 필요할 것으로 생각된다. In this study, the concentration of fine indoor dust and the size distribution of fine indoor dust were analyzed by measuring the dust generated during the cleaning process of an indoor office. We measured $PM_{10}$, $PM_{2.5}$, and $PM_{1.0}$ and analyzed the size distributions of dust larger than $0.3{\mu}m$ in diameter during cleaning. The results showed that the concentration of $PM_{10}$ increased rapidly during cleaning, however $PM_{1.0}$ did not increase. Before cleaning with a broom, the fine dust concentration was about $50{\mu}g/m^3$, but increased to about $400{\mu}g/m^3$ as cleaning progressed. In the case of indoor cleaning with a vacuum cleaner, the concentration of $PM_{10}$ increased during the cleaning process and the increase of $PM_{2.5}$ was relatively small. $PM_{1.0}$ did not increase as in the case of cleaning the broom.

에어로졸 중화기의 성능이 고하전 입자의 크기분포 측정에 미치는 영향

지준호,배귀남,황정호,Ji, Jun-Ho,Bae, Swi-Nam,Hwang, Jung-Ho 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.10

A SMPS(scanning mobility particle sizer) system measures the number size distribution of particles using electrical mobility detection technique. An aerosol charge neutralizer, which is a component of the SMPS, is a bipolar charger using a radioactive source to apply an equilibrium charge distribution to aerosols of unknown charge distribution. However, the performance of aerosol charge neutralizers is not well known, especially for highly charged particles. In this study, the effect of the particle charging characteristics of two aerosol charge neutralizers on the measurement using a SMPS system was experimentally investigated for highly charged polydisperse particles. One has radioactive source of $^{85}$ Kr (beta source, 2 mCi) and the other has $^{210}$ Po (alpha source, 0.5 mCi). The air flow rate passing through each aerosol charge neutralizer was changed from 0.3 to 3.0 L/min. The results show that the non-equilibrium character in particle charge distribution appears as the air flow rate increases although the particle number concentration is relatively low in the range of 1.5∼2x10$^{6}$ particles/㎤. The low neutralizing efficiency of the $^{85}$ Kr aerosol charge neutralizer for highly charged particles can cause to bring an artifact in the measurement using a SMPS system. However, the performance of the $^{210}$ Po aerosol charge neutralizer is insensitive to the air flow rate.

모멘트법을 이용한 AC 전기장 내의 단극성 입자의 전기응집 해석

지준호,황정호,Ji, Jun-Ho,Hwang, Jeong-Ho 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.1

A numerical study has been carried out on the evolution of the particle size distribution for unipolar charged particles that experience coagulation in an alternating electric field. The collision frequency function of charged particles was analytically derived. The log-normal size distribution function is utilized for representing a poly-disperse size distribution and the moments of the particle size distribution are used to solve the general dynamic equation considering only AC electric force effect. The results are compared with the effects of brownian coagulation.

초미세먼지 주의보 시 지식산업센터 사무실의 실내 초미세먼지 농도 특성과 공기청정기와 환기장치의 영향

지준호,주상우,Ji, Jun-Ho,Joo, Sang-Woo 한국입자에어로졸학회 2020 Particle and Aerosol Research Vol.16 No.3

본 연구에서는 초미세먼지 주의보가 발효된 2019년 3월 4일~7일까지 약 80시간 동안 국내 지식산업센터 사무실 내 실내 미세먼지와 초미세먼지 농도를 측정하였다. 측정이 이루어지는 동안 공기청정기와 환기장치의 구동에 의한 영향을 확인하였고, 초미세먼지 주의보 날의 실내와 실외의 입자 크기분포를 분석하였다. 사무실의 테라스 쪽 이중 창문과 복도쪽 입구 출입문을 모두 닫은 밀폐 조건에서 실외 대비 실내의 초미세먼지 농도비는 약 40% 정도를 유지했다. 초미세먼지 주의보의 시기에 중성능급 필터가 장착된 환기장치의 풍량을 1단이나 2단으로 운전한 경우에도 외기 대비 실내 초미세먼지 농도는 환기하지 않고 밀폐만 했을 때의 조건과 비슷했다. 환기장치를 구동하지 않고, 문을 닫아둔 조건에서 공기청정기를 가동하면 실내 초미세먼지 농도를 초미세먼지 주의보 시에도 대기 초미세먼지 농도대비 약 20% 수준으로 감소시킬 수 있었지만, 환기장치의 풍량을 증가시켜 가동하면, 상대적으로 환기를 통해 미세먼지를 공급하는 공기량이 증가하여, 공기청정기의 효과가 감소하였고, 실내외 농도비를 약 36%로 유지하는 것을 확인하였다. 사무실 내 실내 부유 먼지의 크기분포의 분석 결과 1 ㎛ 보다 큰 입자의 농도는 매우 낮았다. 대기의 입자 크기분포는 1 ㎛ 이하의 입자의 봉우리와 1~10 ㎛ 입자의 봉우리의 두 부분으로 나타나는데 비해, 실내 입자의 크기분포에서는 1~10 ㎛ 입자의 봉우리가 사라지고 1 ㎛ 이하의 입자의 봉우리만 남는 형태로 상대적으로 큰 입자의 농도가 미미했다. 사무실의 밀폐가 초미세먼지 농도의 감소에 효과가 있었지만, 대부분은 1 ㎛ 보다 큰 입자가 제거되었고, 인체에 더 영향을 미치는 1 ㎛ 이하의 입자는 실내로 쉽게 침투하였다. 결국 밀폐된 사무실 실내에서 공기청정기의 사용은 1 ㎛ 이하의 인체에 더 해로운 크기의 입자를 제거하는데 큰 효과를 얻을 수 있음을 확인하였다. 본 연구는 단지 80시간의 짧은 시간의 실증 데이터를 분석한 결과이지만, 초미세먼지 주의보가 1년 중 1주일 이내로 발생하는 한정된 기간에 발생한다는 점에서 측정 및 분석 데이터가 중요한 의미를 갖는다고 생각된다. 또한 실내 초미세먼지 농도에 영향을 미치는 다양한 변수들을 고려하여 측정 계획을 작성하여 실증 측정이 이루어졌기 때문에 비교적 신뢰성 있는 분석데이터를 제시할 수 있었다. In this study, the indoor fine dust concentration in an office of the Korea Knowledge Industry Center was measured for about 80 hours when the concentration of atmospheric PM_2.5 was very high. The effect of the operation of the air cleaner and the forced ventilation system on the indoor PM_2.5 was investigated, and the particle size distribution of the indoor and outdoor particles was analyzed. When forced ventilator and air purifiers were partially used, the indoor PM_2.5 concentrations were maintained between 27.7 ㎍/㎥ and 32.9 ㎍/㎥ when the atmospheric PM_2.5 was 127.7 ㎍/㎥ to 141.6 ㎍/㎥ during working hours. It is more effective to operate the air purifier without operating the forced ventilation system when the concentration of the PM_2.5 is high since the PM_2.5 penetrating the installed filter is continuously introduced indoor from the outside.