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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.
태양열 집열기 적용을 위한 순수 물과 에탄올 탄소나노유체의 특성 비교 연구
안응진(An Eoung-Jin),박성식(Park Sung-Seek),천원기(Chun Won-gee),박윤철(Park Yoon-Chul),김남진(Kim Nam-Jin) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.3
In this study, for increasing the efficiency of solar collector, the thermal conductivities and viscosities of the pure water and ethanol oxidized multi-walled carbon nanofluids were measured Nanofluids were manufactured by ultra-sonic dispersing oxidized multi-walled carbon nanotubes(OMWCNTs) in the pure-water and ethanol at the rates of 0.0005 ~ 0.1 vol%. the Thernal conductivities and viscosities of manufactured nanofluids were measured at the low temperature(10℃), the room temperature(25℃) and the high temperature(70℃). For measuring thermal conductivity and viscosity, we used Transient Hot-wire Method and Rotational Digital Viscometer, respectively. As a result, under given temperature conditions, thermal conductivity of the 0.1 vol% pure-water nanofluid improved 7.98% (10℃), 8.34% (25℃), and 9.14% (70℃), and its viscosity increased by 37.08% (10℃), 33.96% (25℃) and 21.64% (70℃) than the base fluids. Thermal conductivity of the 0.1 vol% ethanol nanofluids improved 33.72% (10℃), 33.14% (25℃), and 32.36% (70℃), and its viscosity increased by 37.93% (10℃), 31.92% (25℃) and 29.42% (70℃) than the base fluids.
안응진(An, Eoung-Jin),박성식(Park, Sung-Seek),김남진(Kim, Nam-Jin) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.05
탄소나노튜브는 높은 전기 전도성과 열 전도성을 가지며, 이러한 특성 때문에 21세기를 주도해 나갈 수 있는 차세대 첨단 소재로서 각광을 받고 있다. 또한 최근에는 나노공학기술의 발달로 인하여 획기적으로 높은 열전도도를 나타내는 다중벽 탄소나노튜브(Multi-walled Carbon Nanotubes, MWCNTs)의 대량 생산이 가능하게 되면서 다중벽 탄소나노튜브의 높은 열전도도 특성을 이용하여 탄소나노튜브를 기본 유체 및 기능성 유체에 안정하게 분산 시킨 후 이를 이용하고자 하는 연구가 활발히 진행되고 있으며, 탄소나노튜브를 유체에 안정하게 분산시키기 위한 방법으로는 기계적 분산법, 물리적 흡착에 의한 분산법, 화학적 개질에 의한 분산법이 있다. 따라서 본 연구에서는 이들 분산 방법과 탄소나노튜브 입자의 물성치에 따른 나노유체의 특성을 알아보기 위하여 나노유체의 열전도도와 점도 특성을 비교 분석하였다. 모든 물성치는 같지만 탄소나노튜브의 길이만 다른 두 종류의 다중벽 탄소나노튜브에 각각 계면 활성제(Sodium Dodecyl Sulfate, SDS) 100 wt%와 고분자 화합물(Polyvinyl Pyrrolidone, PVP) 300 wt%를 첨가하여 나노유체를 제조하였으며, 산화처리 된 다중벽 탄소나노튜브(Oxidized Multi-Walled Carbon Nanotubes, OMWCNTs)를 증류수에 초음파 분산하여 산화나노유체를 제조하였다. 나노유체의 열전도도는 전기 전도성 유체의 비정상 열선법(Transient Hot-wire Method)을 이용하여 측정하였고, 나노유체의 점도는 회전형 디지털 점도계를 이용하여 측정하였다. 실험 결과, 상온에서 동일 혼합비의 나노유체를 비교했을 때, 산화나노유체가 SDS 100 wt%, PVP 300 wt%를 혼합한 다른 나노유체보다 높은 열전도도 특성을 보였으며 점도 특성 또한 가장 낮은 것으로 측정되었다. 특히 상온에서 0.1vol%의 산화 CM-100 나노유체는 증류수보다 열전도도가 8.34%가 증가하였고, 10?C의 저온에서는 상온에서 증류수와 비교하여 측정된 열전도도 값보다 0.36%가 감소한 7.98%가 증가함을 보였다. 본 연구를 통하여 얻어진 결과는 높은 열전도도를 필요로 하는 열교환기의 작동유체나 기타 활용 분야에 대한 기초 자료로써 유용한 정보를 제공할 것이라 판단된다.
결합(Coupling)된 열음향 레이저의 음향파 특성 비교 분석
김남진(Nam-jin Kim),안응진(Eoung-jin An),박성식(Sung-seek Park),오승진(Seung-jin Oh),천원기(Won-gee Chun) 한국에너지기후변화학회 2012 에너지기후변화학회지 Vol.7 No.1
In this study, for investigating the interaction of coupling sound waves, we generated two thermoacoustic laser(TAL) and measured sound pressure level and waveform of TAL. The TAL systems was crossed 0˚, 30˚ and 90˚. And the distance of TAL systems was increased by 2㎝. As a result, when angle of two TAL system was 0˚, the synchronization of sound waves and phase locking were not observed. when angle of two TAL system was 30˚ and 90˚, the synchronization of sound waves and phase locking were observed. By increasing distance of TAL system, the synchronization of sound waves and phase locking were not observed.
메탄 하이드레이트 생성을 위한 THF와 산화 탄소나노튜브의 영향에 대한 비교 연구
박성식(Sung-Seek Park),안응진(Eoung-Jin An),김남진(Nam-Jin Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.12
Methane hydrate is formed by physical binding between water molecules and methane gas, which is captured in the cavities of water molecules under the specific temperature and pressure. 1 ㎥ hydrate of pure methane can be decomposed to the methane gas of 172 ㎥ and water of 0.8 ㎥ at standard condition. Therefore, there are a lot of practical applications such as separation processes, natural gas storage transportation and carbon dioxide sequestration. For the industrial utilization of hydrate, it is very important to rapidly manufacture hydrate. So in this study, hydrate formation was experimented by adding THF and oxidized carbon nanotubes in distilled water, respectively. The results show that when the oxidized carbon nanofluids of 0.03 wt% was, the amount of gas consumed during the formation of methane hydrate was higher than that in the THF aqueous solution. Also, the oxidized carbon nanofluids decreased the hydrate formation time to a greater extent than the THF aqueous solution at the same subcooling temperature.
박성식(Sung-Seek Park),안응진(Eoung-Jin An),김남진(Nam-Jin Kim) 한국에너지기후변화학회 2011 에너지기후변화학회지 Vol.6 No.1
Methane hydrate is formed by physical binding between water molecules and methane gas, which is captured in the cavities of water molecules under the specific temperature and pressure. When methane hydrate is artificially formed, there is no repeatability at the repetition experiments of the same conditions. Therefore, for the practical purpose in the application, the present investigation focuses on the repeatability through the experiments on methane hydrate formation time and gas consumption. The results showed that the hydrate formation was a stochastic phenomenon. However, if the water was agitated by magnetic stirrer or the subcooling temperature was increased, the stochastic phenomenon was depressed.
박성식(Park Sung-Seek),안응진(An Eoung-Jin),오승진(Oh Seung-Jin),천원기(Chun Won-Gee),김남진(Kim Nam-Jin) 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.2
The conversion of solar energy into acoustic waves is experimentally studied. Measurements were made on the Sound Pressure Level (SPL), frequency, onset time and the temperature gradient across the stack. A pyrex resonance tube is used with a honey-comb structure ceramic stack along with Ni-Cr and Cu wires. An AL1 acoustical analyzer was used to measure the SPL and frequency of acoustic waves whereas K-type thermocouples were hired to estimate temperature gradients. For a resonance tube of 100㎜, no acoustic waves were generated with a power input of 25W. By increasing its length to 200㎜, however, maximum SPLs of 96.4㏈, 106.3㏈ and 112.8㏈ were detected for the tubes of 10㎜, 20㎜ and 30㎜ in IDs and their respective stack positions of 70㎜, 60㎜ and 50㎜ from the closed end.
감압법을 이용한 메탄 하이드레이트 생산에 대한 실험적 연구
박성식(Sung-Seek Park),안응진(Eoung-Jin An),황종대(Jong-Dae Hwang),현창해(Chang-Hae Hyun),김남진(Nam-Jin Kim) 한국에너지기후변화학회 2012 에너지기후변화학회지 Vol.7 No.1
Natural gas hydrate has been considered as the next generation energy resource, because it is mainly composed of methane and it has a large amount of deposits in many deep-water and permafrost regions of the world widely. However, production of methane gas from natural gas hydrate is required to a high level of technology. Because of about 97% of natural gas hydrates have been located offshore, and only 3% on land. So in this study, production of methane gas from methane hydrate was experimented by using depressurizetion. Experimental apparatus of methane gas production has been designed to storage producted gas from hydrate, And the sedimentary layers were made by using artificial silica sand inside hydrate reactor. As a results, the amount of producted methane gas was different as a particle size and porosity. Also, depressurizaion points of gas non-production were increasingly reduced to the bigger the particle size and the porosity.