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다중벽 탄소나노튜브가 첨가된 나노유체의 특성에 대한 연구
박성식(Sung-Seek Park),박윤철(Youn Cheol Park),김남진(Nam-Jin Kim) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
In this study, the characteristics of multi-walled carbon nanotubes added nanofluid were investigated. Sodium Dodecyl Sulfate, SDS, and Polyvinylpyrrolidone, PVP, were employed as the dispersant. SDS or PVP was added in pure water. And then, 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.01, and 0.02 vol% of CM-95 and CM-100 were dispersed respectively. The thermal conductivity and the viscosity were measured with a transient hot-wire instrument built for this study and the DV II+ Pro viscometer. The results showed that PVP had good thermal conductivity at 300 wt% and the thermal conductivity of CM-100 was better than that of CM-95. However, the viscosity of CM-100 was higher than that of CM-95.
그래핀과 탄소나노튜브 나노유체의 열전도도 특성 비교연구
박성식(Park, Sung-Seek),김남진(Kim, Nam-Jin) 한국태양에너지학회 2013 한국태양에너지학회 학술대회논문집 Vol.2013 No.4
Recently, high-thermal-conductivity graphene and carbon nanotube nanoparticles have attracted particularly close attention from researchers. In the present study, the thermal conductivity and viscosity properties of two kinds of graphene and carbon nanotube nanofluids added to distilled water — two graphenes and carbon nanotubes of differing size — were compared and analyzed. The thermal conductivities of the nanofluids, formulated in the usual manner by adding graphene and carbon nanotube to distilled water and subjecting the mixture to ultrasonic dispersion, were measured by the transient hot-wire method, and the viscosities were determined using a rotational digital viscometer. As a result, we concluded that the nanofluid of small particle diameter have outstanding properties as heat transfer media, due to their excellent thermal conductivity and viscosity, compared with the other nanofluid.
박성식(Park, Sung-Seek),김남진(Kim, Nam-Jin) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.11
A nanofluid is a fluid containing suspended solid particles, with sizes on the order of nanometers. Specially, graphene exhibited high thermal characteristic of added many nanoparticles in nanofluids is attracting a lot of attention. Graphene is a flat monolayer of sp<SUP>2</SUP>-bonded carbon atoms tightly packed into a honeycomb lattice. And graphenes are known to have very high thermal conductivity. Therefore, we compared the thermal conductivity with the viscosity of graphene M-5 nanofluids and graphene M-15 nanofluids. Graphene M-5 and graphene M-15 are different average particle diameter and the other properties are same. Two kinds of graphene nanofluids was examined by measuring thermal conductivity via transient hot-wire method. And the viscosity was measured by using rotational digital viscometer. As a result, graphene M-5 nanofluids exhibited better thermal conductivity and viscosity than graphene M-15 nanofluids.
박성식(Park Sung-Seek),김남진(Kim Nam-Jin) 한국태양에너지학회 2010 한국태양에너지학회 논문집 Vol.30 No.5
Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity and each other from physically-bond at specially temperature and pressure condition. 1㎥ of methane hydrate can be decomposed into the maximum of 216㎥ of methane gas under standard condition. If these characteristics of hydrate are utilized in the opposite sense, natural gas can be fixed into water in the form of a hydrate solid. Therefore the use of hydrate is considered to be a great way to transport and store natural gas in large quantity. However, when methane hydrate is formed artificially, the amount of gas that is consumed is relatively low, due to the slow reaction rate between water and methane gas. Therefore for practical purposes in the application, the present investigation focuses on increasing the amount of gas consumed by adding chemically oxidized OMWCNTs to pure water. The results show that when 0.003 wt% of oxidation multi-walled carbon nanotubes was added to pure water, the amount of gas consumed was almost four times more than that of pure water indicating its effect in hydrate formation and the hydrate formation time decreased at alow subcooling temperature.
박성식(Park Sung-Seek),김남진(Kim Nam-Jin) 한국태양에너지학회 2009 한국태양에너지학회 논문집 Vol.29 No.4
I ㎥ hydrate of pure methane can be decomposed to the maximum of 216 ㎥ methane at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore, the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18-24% less than the liquefied transportation. In the present investigation, experiments and theoretical calculation carried out for the formation of methane hydrate in NaCl 3.5wt% solution. The results show that the equilibrium pressure in seawater is more higher than that in pure water, and methane hydrate could be formed rapidly during pressurization if the subcooling is maintained at 9K or above in seawater and 8K or above in pure water, respectively. Also, amount of consumed gas volume in pure water is more higher that in seawater at the same experimental conditions. Therefore, it is found that NaCI acts as a inhibitor
그래핀 입자의 크기와 혼합비율이 나노유체의 비등 열전달에 미치는 영향에 대한 실험적 연구
박성식(Park Sung-Seek),김영훈(Kim Young Hun),김남진(Kim Nam-Jin) 한국태양에너지학회 2015 한국태양에너지학회 논문집 Vol.35 No.2
Boiling heat transfer characteristic is very important in the various industries such as solar thermal system, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. Therefore, in this study, boiling heat transfer characteristics such as critical heat flux (CHF) and heat transfer coefficient under the pool boiling state were tested using graphene nanofluids. Graphene used in this study, which have the same thermal conductivity but with different sizes. The experimental results showed that the highest the CHF and boiling heat transfer coefficient increase ratio for graphene nanofluids was at the 0.01 vol.%. At the present juncture, the CHF and boiling heat transfer coefficient increase ratio of the small-sized graphene nanofluids was higher than the large-sized graphene nanofluids.
그래핀과 탄소나노튜브의 형상에 따른 나노유체의 열전도도 특성 비교 연구
박성식(Park Sung-Seek),한상필(Han Sang-Pil),전용한(Jeon Yong-Han),김종윤(Kim Jong-Yoon),김남진(Kim Nam-jin) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.3
Recently, high-thermal-conductivity graphene and carbon nanotube nanoparticles have attracted particularly close attention from researchers. In the present study, the thermal conductivity and viscosity properties of two kinds of graphene and carbon nanotube nanofluids added to distilled water - two graphenes and carbon nanotubes of differing size - were compared and analyzed. The thermal conductivities of the nanofluids, formulated in the usual manner by adding graphene and carbon nanotube to distilled water and subjecting the mixture to ultrasonic dispersion, were measured by the transient hot-wire method, and the viscosities were determined using a rotational digital viscometer. As a result, we concluded that the nanofluid of small particle diameter of graphene have outstanding properties as heat transfer media, due to their excellent thermal conductivity and viscosity, compared with the other nanofluid.
박성식(Park Sung-Seek),김남진(Kim Nam-Jin) 한국태양에너지학회 2010 한국태양에너지학회 논문집 Vol.30 No.3
Ocean Thermal Energy Conversion(OTEC) power plants have been examined as a viable option for supplying clean energy. This paper evaluated the thermodynamic performance of the OTEC Power system for the production of electric power and desalinated water. The results show that newly developed fluids such as R32, R125, R143a, and R410A that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. Overall cycle efficiency of open cycle is the lowest value of 3.01% because about 10% of the gross power is used for pumping out non-condensable gas. Also, the hybrid cycle is an attempt to combine the best features and avoid the worst features of the open and closed cycles. The overall cycle efficiency of hybrid cycle is 3.44% and the amount of desalinated water is 0.0619 ㎏/s.
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.
나노유체 : 탄소나노튜브 입자의 크기 및 혼합비율 변화에 따른 나노유체의 임계열유속 특성 비교 연구
박성식 ( Sung Seek Park ),전용한 ( Yong Han Jeon ),김남진 ( Nam Jin Kim ) 한국액체미립화학회 2013 한국액체미립화학회 학술강연회 논문집 Vol.2013 No.-
Critical heat flux (CHF) phenomenon describes the thermal limit where a phase change occurs during heating, which suddenly decreases the efficiency of heat transfer coefficient, thus causing localized overheating of the heating surface. And the condition of CHF is used in many types of thermal system, such as power generation including nuclear power plants, heat exchangers, refrigeration, high-density electronic, etc. Therefore, Enhancement of CHF is essential for economy and safety of heat transfer system. Recently, the CHF reported increased when applied to nanofluids. In the present study, the CHF characteristics of two types of carbon nanotube nanofluids - two carbon nanotubes of differing size - were compared and analyzed as a function of the volume fraction. As a result, two types of nanofluids are the highest CHF at 0.001 vol%, and the CHF of two nanofluids increased along with the volume fraction until 0.001 vol%. It is confirmed that the sized of carbon nanotube influences the CHF of nanofluid, and the rate of CHF increase of nanofluid, with longer carbon nanotube particles, is higher than that of the other nanofluid.