• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2009-2014
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• 2007

Hydrogen is a fuel of fuel cell system, which has powerful explosion possibility. Hence, the fuel cell system needs safety evaluation to prevent risk of hydrogen leakage. We use a actual size chamber of a common fuel cell module to analyze hydrogen. Hydrogen injection holes are located in lower part of the chamber in order to simulated hydrogen leakage. The hydrogen sensor can detect range of 0${\sim}$4%. Since the hydrogen gas, of which leaked amount is controled by MFC, are injected at the bottom holes, the transient sensor signals are measured. At a condition of 10cc/s of hydrogen leakage, the sensor detects hydrogen leakage after 22sec and there is also several seconds of time delay depending on the position of the sensor. This experimental data can be applied for the design of the hydrogen detection system and ventilation system of a residential fuel cell system.

• 설비공학논문집
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• 제14권7호
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• pp.531-542
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• 2002

Transcritical$CO_2$ systems are under consideration for use as residential/mobile air conditioners. In these systems, an internal heat exchanger is usually adopted to improve both capacity and/or COP of the $CO_2$ system in lower operating pressure range of gas cooler. A program has been developed to analyse the performance of internal heat exchangers using the section-by-section method. The internal heat exchanger of coaxial configuration is first analyzed and fairly good agreements with the data are obtained, And then the internal heat exchanger of multiple circular coil configuration has been investigated. The results obtained from the parametric study provide the guidelines for the initial design and manufacturing concepts of the internal heat exchanger in transcritical $CO_2$ system. Further studies are necessary to develop the heat transfer correlations of carbon dioxide in the tubes to obtain more accurate results.

• 한국가스학회지
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• 제10권3호
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• pp.54-59
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• 2006

가정용 LPG 가스시설에 사용되고 있는 압력조정기에서 체결된 호스가 분리되거나 또는 고의로 절단하여 발생하는 가스사고 및 고의사고를 예방하기 위해서 조정기 출구에 차단기능을 갖는 안전장치를 개발하였다. 본 연구를 통하여 개발된 차단안전장치의 작동성과 현장 적용여부를 확인하기 위하여 조정기의 설치상태에 따른 시험과, 가정집에서의 현장시험을 실시하였다. 시험결과 입구압력 $0.07{\sim}1.56MPa$의 조건에서 조정기의 설치상태와는 무관하게 호스길이 5 m이내에서 차단되었고, 차단유량은 수직상향, 수평, 수직하향의 순서로 높게 나타났다. 또한 가정집에 설치하여 5개월 시험한 결과, 가스레인지나 보일러를 사용하는데 있어 문제점은 없는 것으로 나타났다. 개발된 조정기 차단안전장치가 상용화되어 보급된다면 호스분리나 절단에 따른 사고를 대폭적으로 예방하는데 크게 기여할 수 있을 것으로 기대된다.

• 에너지공학
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• 제8권2호
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• pp.242-247
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• 1999

각종 산업단지 및 발전소에서 배출되는 막대한 양의 폐열을 회수하여 재활용하기 위하여 전국 7개 지역 11개 공단에 대한 폐열 특성분석을 실시하였다. 본 연구는 도시종합에너지시스템 연구의 일환으로 산업체 폐열을 배후도시의 주거 및 상업지역에 공급.이용 가능성을 검토하였다. 검토대상 공업단지의 조사된 폐열량은 148,913 TOE/년으로 나타났으며, 온도범위는 $0^{\circ}C$~20$0^{\circ}C$가 83%, 그리고 배가스 형태로 배출되는 폐열이 전체의 82%를 차지하는 것으로 나타났다. 이들 조사대상 공업단지 중 폐열량이 집중된 4개 지역 (대구공단, 울산 석유화학단지, 여천 석유화학단지 및 전주공단)에 대한 폐열특성도 상세하게 조사되었으며, 이들 공단의 조사된 폐열량은 114,402 TOE/년으로 조사된 총폐열량의 77%에 해당하며. 이중 배가스는 87%, 온도범위는 $0^{\circ}C$~20$0^{\circ}C$의 폐열이 대부분인 것으로 나타났다. 또한, 18.1 million TOE/년의 폐열이 화석연료를 사용하는 발전소로부터 발생되며, 이중 95%가 복수냉각기에서 배출되는 27$^{\circ}C$~34$^{\circ}C$ 범위의 저온폐열이며, 나머지 5%(894,800 TOE/년)가 연도 배가스 형태로 배출되고 있는 것으로 조사되었다.

• Journal of Radiation Protection and Research
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• 제40권3호
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• pp.155-161
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• 2015

Radon is a naturally occurring radioactive gas and a major indoor contribution of exposure to ionizing radiation in dwellings. $^{222}Rn$ is a health hazard gas what is responsible for thousand lung cancer deaths every year. In this study, indoor radon concentrations present in thirty representative houses in Mahallat city, Iran, were determined in order to estimate lung cancer risk associated with residential radon exposure. Long-term passive method, using CR-39, was used to measure the radon concentration. The results showed an association between the age of the dwellings and the indoor radon concentration that was found, in that the concentration of radon tended to increase as the age of the dwelling also increased. The indoor radon concentrations were calculated to be within the range of $23{\pm}2$ to $350{\pm}26Bq{\cdot}m^{-3}$, with an average of $158Bq{\cdot}m^{-3}$. The annual effective dose from inhaled radon and its decay products was calculated between $0.8{\pm}0.1$ and $12.3{\pm}0.9mSv{\cdot}y^{-1}$, with an average of $5.5mSv{\cdot}y^{-1}$. By taking into consideration the EPA recommendation and ICRP statement, the average annual risk of lung cancer from inhaled radon was calculated as 0.09%, 0.06%, 0.01%, and 0.03% for current smokers (CS), those who had ever smoked (ES), never smokers (NS) and the general population, respectively.

• 한국대기환경학회지
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• 제24권1호
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• pp.16-29
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• 2008

Nitrous acid (HONO) can be produced by heterogenous reactions of nitrogen dioxide on surface materials and direct emission from combustion sources. However, a little is known of indoor HONO levels or the relationship between residential HONO, NO, and $NO_2$ concentrations in occupied houses. Therefore, we measured simultaneously NO, $NO_2$, and HONO concentrations in living room of an apartment using continuous analyzers to study the production of HONO (June $22{\sim}30$, 2006). The 4-min average concentrations of indoor NO, $NO_2$, and HONO were 4.3 (range: $0.4{\sim}214.3$), 10.3 ($2.0{\sim}87.3$), and 1.8 ppb ($0.3{\sim}7.7$), respectively. Peak levels of HONO up to 7.7 ppb and 24-hr averages as high as 1.7 ppb were measured. In agreement with previous studies, indoor HONO concentrations increased during operation of an unvented gas range. Examination of the observed kinetics suggests that the secondary production of indoor HONO, possibly as a result of heterogeneous reactions involving $NO_2$ and $H_2O$ is associated with $[NO_2]^2[H_2O]\;(r^2=0.88)$ rather than with $[NO][NO_2][H_2O]\;(r^2=0.75)$. Three combustion experiments at nighttime were also carried out to investigate the effects of vented combustion on the HONO, NO, and $NO_2$ concentrations. It was found to release HONO for $10{\sim}15$ minutes after NO and $NO_2$ source was turned off, and peak values were finally attained. Compared to unvented combustion, peak $NO_2$ and HONO concentrations were 3.2 and 2.0 times lower at weak vented combustion (air flow: $340\;m^3/hr$) and 4.9 and 2.4 times lower at strong vented combustion (air flow: $540\;m^3/hr$), respectively, emphasizing importance of operating ventilation hood fan during combustion to improve indoor air quality.

• 분석과학
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• 제16권3호
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• pp.240-248
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• 2003

공업지역에서 악취원인물질로 잘 알려진 황화물은 매우 낮은 최소 후각감지농도를 나타낸다. 여러 악취발생원 주변의 대기 중 미량의 황화합물을 아르곤에서 농축시켜 선택성과 감도가 우수한 불꽃 광도 검출기 (FPD)가 장착된 가스크로마토그래프를 이용하여 측정하였다. 25% ${\beta}$,${\beta}$-Oxydipropionitrile, 60/80 Chromosob W가 저온농축을 위한 흡착제로 되었으며 이를 충전 유리컬럼의 충전제로도 사용하였다. 악취시료의 농축량은 0.1~3.0L 범위에서 채취장소에 따라 달리하였다. 주거지역과 사업장 부지경계선상에서의 공기 및 하수처리장과 같은 공업지역 내 사업장의 배출구 가스 중의 휘발성 황화합물의 농도를 측정하였다.

• 한국산업보건학회지
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• 제27권1호
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• pp.38-45
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• 2017

Objectives: Radon may be second only to smoking as a cause of lung cancer. Radon is a colorless, tasteless radioactive gas that is formed via the radioactive decay of radium. Therefore, radon levels can build up based on the amount of radium contained in construction materials such as phospho-gypsum board or when ventilation rates are low. This study provides our findings from evaluation of radon gas at facilities and offices in an industrial complex. Methods: We evaluated the office rooms and processes of 12 manufacturing factories from May 14, 2014 to September 23, 2014. Short-term data were measured by using real-time monitoring detectors(Model 1030, Sun Nuclear Co., USA) indoors in the office buildings. The radon measurements were recorded at 30-minute intervals over approximately 48 hours. The limit of detection of this instrument is $3.7Bq/m^3$. Also, long-term data were measured by using ${\alpha}-track$ radon detectors(${\alpha}-track$, Rn-tech Co., Korea) in the office and factory buildings. Our detectors were exposed for over 90 days, resulting in a minimum detectable concentration of $7.4Bq/m^3$. Detectors were placed 150-220 cm above the floor. Results: Radon concentrations averaged $20.6{\pm}17.0Bq/m^3$($3.7-115.8Bq/m^3$) in the overall area. The monthly mean concentration of radon by building materials were in the order of gypsum>concrete>cement. Radon concentrations were measured using ${\alpha}-track$ in parallel with direct-reading radon detectors and the two metric methods for radon monitoring were compared. A t-test for the two sampling methods showed that there is no difference between the average radon concentrations(p<0.05). Most of the office buildings did not have central air-conditioning, but several rooms had window- or ceiling-mounted units. Employees could also open windows. The first, second and third floors were used mainly for office work. Conclusions: Radon levels measured during this assessment in the office rooms of buildings and processes in factories were well below the ICRP reference level of $1,000Bq/m^3$ for workplaces and also below the lower USEPA residential guideline of $148Bq/m^3$. The range of indoor annual effective dose due to radon exposure for workers working in the office and factory buildings was 0.01 to 1.45 mSv/yr. Construction materials such as phospho-gypsum board, concrete and cement were the main emission sources for workers' exposure.