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An Experimental Study on the Utilization of Heat Pipes for Solar Water Heaters
천원기,강용혁,전명석,곽희열,Chun, Won-Gee,Kang, Yong-Heack,Jeon, Myung-Seok,Kwak, Hee-Youl 한국태양에너지학회 1995 한국태양에너지학회 논문집 Vol.15 No.2
본 논문은 히이트 파이프를 이용한 태양열 온수 급탕 시스템의 제작 및 그 열성능에 관한 내용이다. 국내 기후에 적합한 모델을 도출하기 위하여 본 연구에서는 여러번에 기초실증 실험을 수행하였다. 히이트 파이프는 구리로 제작하였으며 증발부, 단열부 및 응축부의 길이는 각각 1700mm, 100mm, 그리고 200mm이다. 증발부는, 특히 효율적인 집열을 위하여 얇은 구리로 만든 핀(fin)을 부착하였다. 연구결과를 살펴보면 작동 유체의 종류, 윅(wick)의 유무, 표면 처리 정도 그리고 그 밖의 여러 설계인자에 따라 히이트 파이프를 이용한 태양열 온수 급탕 시스템의 열성능이 적지 않은 영향을 받을 수 있음을 나타내고 있다. This paper reports the performance of solar domestic hot water systems manufactured with heat pipes. A series of tests were conducted on a number of systems to elicit the most suitable configuration of the system for possible commercialization in Korea. The heat pipe is made with a copper tube and the respective length of the evaporator, adiabatic, and condenser sections are 1700mm, 100mm and 200mm. The evaportor section is finned with a copper plate to increase solar input for its proper operation as a heat pipe. Results show quite an interesting performance data stemming from the difference in working fluids, presence of wick, and other various design parameters associated with the collection and utilization of solar energy.
저온 활용 시스템의 효율 제고를 위한 마찰 저항 감소 연구
천원기(Won Gee Chun),김철암(Chul Am Kim),성준희(Jun Hee Sung),최형진(Hyoung Jin Choi),김종보(Chong Bo Kim),김형택(Hyung Taek Kim) 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.4
본 연구에서는 회전원판 장치를 사용하여 난류 유동장에서의 고분자에 의해 유도되는 마찰저항 감소효과에 대하여 조사하였다. 해양온도차 발전에서 해수를 이동시키는 유동장은 난류상태로 이러한 난류계에 대하여 마찰저항 감소는 충분한 적용가치가 있다. 네가지의 분자량이 다른 PEO를 마찰저항 첨가제로, 실험실에서 제조한 인공해수를 용매로 사용하여 고분자의 분자량, 고분자의 농도와 원판의 회전속도와 같이 마찰저항 감소효과에 영향을 줄 수 있는 여러 인자들에 대해서 살펴보았다.<br/> 마찰저항 감소의 농도의존성은 Virk의 Universal correlation를 따르는 것을 확인하였다. 해수에서도 PEO와 용매간의 Universal 곡선이 증류수를 용매로 하였을 때와 동일함을 확인하였다. Drag reduction produced by the dilute solution of polymer under turbulent flow in a rotating disk apparatus (RDA) was investigated in this study for the purpose of potential application to the Ocean Thermal Energy Conversion (OTEC) system, Four different molecular weights of poly(ethylene oxide) (PEO) were used as drag reducing additives, and synthetic seawater was adopted as a solvent. Experiments were undertaken to observe the dependence of drag reduction on various factors such as polymer molecular weight, polymer concentration and the rotating speed of the disk. The concentration dependence on the drag reduction of this polymer system was shown to obey an empirical drag reduction equation of the Virk's universal correlation.
천원기(Chun Won-gee),임상훈(Lim Sang-Hoon),전명석(Jeon Myung-Seok),윤종호(Yoon Jong-Ho) 한국태양에너지학회 1992 한국태양에너지학회 논문집 Vol.12 No.1
본 연구에서는 f-chart method를 이용하여 대전지방에서 공기식 시스템을 적용하였을 경우의 난방효과에 대한 성능 분석을 수행하였다. 공기의 유량, 집열판 덮개의 수, 페블베드의 축열 용량 그리고 집열판의 코팅 등에 따른 공기식 시스템의 난방 효과를 분석하였으며 아울러 액체식 시스템을 이용한 난방 시스템과도 동일 조건하에서 그 성능을 비교 분석하였다. The present study has carried out thermal performance evaluation of air systems for space heating in Daejeon by the f-chart method. The various effects with the .change in air flow rate, number of glazings, storage capacity of pebble bed, and coating materials of absorber plate are analyzed with regard to the effectiveness of air systems for space heating. A comparison is also made with liquid systems under the same operating conditions.
순수 물과 에탄올 산화 탄소나노유체의 열전도도 및 점도 특성 비교 연구
안응진,박성식,천원기,박윤철,전용한,김남진,An, Eoung-Jiw,Park, Sung-Seek,Chun, Won-Gee,Park, Yoon-Chul,Jeon, Youn-Han,Kim, Nam-Jin 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.suppl3
Nanofluids are advanced concept fluid that solid particles of nanometer size are stably dispersed in fluid likes water, ethylene glycol and others. They have higher thermal conductivities than base fluids. If using this characteristic, efficiencies of heat exchangers can be increased. Therefore in this study, we measured thermal conductivity and viscosity of carbon nanofluids. They were made to ultra sonic dispersed oxidized multi-walled carbon nanotubes(OMWCNTs) in distilled water and ethanol, respectively. The mixture ratios of OMWCNTs were from 0.0005 vol% ~ 0.1 vol%. Thermal conductivity and viscosity was measured by transient hot-wire method and rotational viscometer. The results of an experiment are as in the following: thermal conductivity of the 0.1 vol% pure-water nanofluid improved 7.98% ($10^{\circ}C$), 8.34% ($25^{\circ}C$), and 9.14% ($70^{\circ}C$), and its viscosity increased by 37.08% ($10^{\circ}C$), 33.96% ($25^{\circ}C$) and 21.64% ($70^{\circ}C$) than the base fluids. Thermal conductivity of the 0.1 vol% ethanol nanofluids improved 33.72% ($10^{\circ}C$), 33.14% ($25^{\circ}C$), and 32.25% ($70^{\circ}C$), and its viscosity increased by 35.12% ($10^{\circ}C$), 32.01% ($25^{\circ}C$) and 19.12% ($70^{\circ}C$) than the base fluids.
감압법을 이용한 메탄하이드레이트 생산에 대한 수치적 연구
김진홍(Kim, Jin-Hong),천원기(Chun, Won-Gee),김남진(Kim, Nam-Jin) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.06
Gas(or methane) hydrates are solid solutions when water molecules are linked through hydrogen bonding and create host lattice cavities that can enclose a large variety of guest gas molecules. The natural gas hydrate crystal may exist at low temperature above the normal freezing point of water and high pressure greater than about 30 bars. A lot of quantities of natural gas hydrates exists in the earth and many production schemes are being studied. In the present investigation, depressurization method was considered to predict the production of gas and the simulation of the two phase flow - gas and water - in porous media is being carried out. The simulation show about the fluid flow in porous media have a variety of applications in industry. Results provide the appearance of gas and water production, the pressure profile, the saturation of gas/ water/ hydrates profiles and the location of the pressure front.
김남진(Kim Nam-Jin),천원기(Chun Won-Gee) 한국태양에너지학회 2008 한국태양에너지학회 논문집 Vol.28 No.6
Methane hydrate is crystalline ice-like compounds which consist of methane gas of 99% and over, and the estimated amount of gas contained in hydrates is about 1 trillion carbon Ton. Therefore, they have the potential for being a significant source for natural gas, and 1㎥ solid hydrates contain up to 172N㎥ of methane gas, depending on the pressure and temperature of production. Such large volumes make natural gas hydrates can be used to store and transport natural gas. In this study, the tests were performed on the fomlation of methane hydrate by a nozzle. The result showed that utilizing nozzles dramatically reduces the time in hydrate formation, the pressure after the injection is decreased to be approximately 90% of experimental pressurethe, and gas consumption is higher about 3 times than that of subcooling test.