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박지훈(Ji-Hoon Park),김내현(Nae-Hyun Kim),최용민(Young-Min Choi),오왕규(Wang-Kyu Oh) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
In this study, an analysis was performed on an evaporative steam generator (concentrator), where natural circulation convective boiling occurs on tube-side by condensing hot steam on shell-side. Existing correlations on two-phase pressure drop, boiling or condensation heat transfer were used for the analysis. The effect of number of tubes, tube length, etc. on thermal performance was investigated. Simulation results reveal that steam generation rate increases almost proportionally to the tube length, or number of tubes. It is also shown that water circulation rate decreases as tube length increases.
극미량 수준의 SF6 측정법에 따른 재현성 및 정확도 향상에 관한 연구
유희정,최홍우,이세표,김종호,한상옥,류상범 한국도시환경학회 2018 한국도시환경학회지 Vol.18 No.4
Kyoto Protocol, adopted in 1997, set the obligation to reduce CO2, CH4, N2O, HFCs, PFCs, and SF6 in developed countries during 1st promised period. SF6 has been drawing a lot of attention since the Kyoto Protocol because once it is released into the atmosphere, it not only stays in the atmosphere for more than 3,200 years but also emits 22,800 times stronger global warming potential at the same concentrations as CO2 if remains in the atmosphere for 100 years. This study introduces 12 methods for SF6 of measuring trace. SF6 of trace level in the atmosphere correctly, the measurement method was changed and as a result, when the back flush method was applied to the pre-concentration system that used low-temperature concentration and high-temperature desorption system, which used Carboxen-1000 adsorption trap, the effect was the best. 오존층의 파괴물질인 CFCs의 대체물로써 SF6의 사용량이 늘어나면서 대기 중의 SF6의 농도가 높아지고 있다. SF6은지구온난화가스중의 하나로써 대기 중에서 3,200년 이상 머무를 뿐만 아니라 온난화지수도 매우 높아 무려 22,800이나된다. 그러나, 대기 중에서의 SF6 농도는 낮은 수준이어서 검출한계이하인 경우가 많다. 본 연구에서는 이러한 극미량 SF6농도를 정확하게 분석하기 위해서 GC-µECD를 이용한 12가지 분석방법을 실험적으로 고찰하였다. 극미량 SF6 농도를가장 정확하게 분석할 수 있는 방법은 Carboxen-1000 물질을 사용한 흡착관과 저온농축 고온탈착 방식의 농축장치에 역추출방식의 분석법을 사용할 경우가 최상의 효율을 나타냈다.
A Study on the Improvement Repeatability and Accuracy of the Analysis Method for SF6 of Trace Level
Heejung Yoo,Hongwoo Choe,Sepyo Lee,Jongho Kim,Sangok Han,Sangboom Ryoo 한국도시환경학회 2018 한국도시환경학회지 Vol.18 No.4
Kyoto Protocol, adopted in 1997, set the obligation to reduce CO2, CH4, N2O, HFCs, PFCs, and SF6 in developed countries during 1st promised period. SF6 has been drawing a lot of attention since the Kyoto Protocol because once it is released into the atmosphere, it not only stays in the atmosphere for more than 3,200 years but also emits 22,800 times stronger global warming potential at the same concentrations as CO2 if remains in the atmosphere for 100 years. This study introduces 12 methods for SF6 of measuring trace. SF6 of trace level in the atmosphere correctly, the measurement method was changed and as a result, when the back flush method was applied to the pre-concentration system that used low-temperature concentration and high-temperature desorption system, which used Carboxen-1000 adsorption trap, the effect was the best.
차상진(Sangjin Cha),이재호(Jae ho Lee),변호원(Ho Won Byun),이을종(Eul jong Lee),김내현(Nae Hyun Kim) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
본 연구에서는 자연순환형 수직증발기 내의 과냉비등 열전달 계수는 검토하였다. 실험을 위해 작은 크기의 모델이 사용되었다. 압력손실계산에 Ueda의 마찰손실 상관식, Saha and Zuber의 건도와 기공율 상관식을 적용하고 열전달 계산에는 Roshenow의 중첩모델을 적용한 결과 모형실험데이터를 잘 예측하였다. In this study, an effort has been made to analyze the subcooled boiling heat transfer in a natural circulation vertical evaporator. To verify the analysis, a small-scale model was made and tested. The friction correlation by Ueda, void fraction and quality correlation by Saha and Zuber along with the superposition heat transfer model by Rohsenow yielded a satisfactory agreement with the model test data.
차상진(Sang-jin Cha),김내현(Nae-Hyun Kim),유진상(Jin-Sang Ryu) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.9
In this study, an effort has been made to analyze the subcooled boiling heat transfer in a natural circulation vertical evaporator. To verify the analysis, a small-scale model was made and tested. The friction correlation by Ueda, void fraction and quality correlation by Saha and Zuber along with the superposition heat transfer model by Rohsenow yielded a satisfactory agreement with the model test data. The analysis was extended to simulate a 1 ton/day concentration system. Comparison with the test results of 1 ton/day prototype revealed that the data were overpredicted by 13%. The capacity of the prototype was 1.2 ton/day with COP of 5.77.
한태헌(Tae Heon Han),김선민(Sun Min Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
We present a theoretical and experimental study of temperature gradient focusing(TGF) exploiting an inherent Joule heating phenomenon. High electric potential applied to the device induces a temperature gradient within the microchannel due to its variable-width geometry, and the temperature-dependent mobility of analytes causes focusing at a specific location.