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나노유체의 임계열유속 및 비등특성에 미치는 나노입자 크기의 영향
조병남(Byeongnam Jo),강준원(Junone Kang),유재석(Jaisuk Yoo),김현정(Hyun-jung Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The characteristics of boiling heat transfer and critical heat flux (CHF) behavior of nano-fluids were studied by using various sized silver and alumina nanoparticles. The diameter of nanoparticles was from 2 ㎚ to 250 ㎚ for silver and from 20㎚ to 40㎚ for alumina. Pool boiling characteristics and CHF enhancement of nano-fluids with different sized nanoparticles were compared with those of pure water and each nano-fluids. The experiment was performed at atmospheric pressure and the temperature of the pool was maintained constantly by using a flat immersed heater. The concentration of nano-fluids was uniform in all experiments as 0.01g/liter. The results showed that the measured boiling curves were shifted to the right. It demonstrated that the occurrence of nucleate boiling regime in nano-fluids retarded, compared with that of pure water. Also, in nano-fluids, the boiling curves showed that CHF of nano-fluids is significantly enhanced and represented the effect of particle size on boiling characteristics.
주름관에서의 압력강하와 마찰손실 측정에 관한 실험적 연구
윤영선(Youngsun Yun),강준원(Junone Kang),김현정(Hyungjung Kim),유재석(Jaisuk Yoo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The data for friction factor of the pipe correlated by Reynolds number and relative roughness has been reported well as a Moody chart. However, the results for corrugated shapes have been not investigated sufficiently. In this research, therefore, the pressure drop and friction factor are obtained. Flexible metal tubes with corrugations for the measurement are made of stainless steel plates. The kinds of tubes for the measurement are 5 annular types and helical types. The pressure drop and the velocity of the flow are obtained by micromanometer & digital pressure sensor, supplying a dry air at several steps. Then the pressure drop was calculated for each tube, using the obtained data. The result showed that the pressure drop is strongly influenced by the viscous dissipation of kinetic energy due to the circulation of flows, rather than a viscous friction loss. The pressure drop increased consistently as the Reynolds number increases.
HFC-152a + Propane 혼합냉매의 기-액 평형에 관한 실험적 연구
이광재(Kwangjae Lee),강준원(Junone Kang),박영무(Youngmoo Park),유재석(Jaisuk Yoo),김현정(Hyunjung Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The equilibrium data of binary systems 1,1-Difluoroethane (R-152a) + Propane (R-290) were measured. Forty equilibrium data for 1,1-Difluoroethane (R-152a) + Propane (R-290) system were measured over the temperature range 273.15~313.15 K at 10 K interval and the composition range 0.2~0.8, respectively. Vapor-liquid equilibrium data were calculated by using equation of state and compared with present data. CSD, PR, RKS equation were used as equation of state. Positive azeotropic mixture are found around a composition x₁=0.73.
이광재(Kwangjae Lee),강준원(Junone Kang),유재석(Jaisuk Yoo),김현정(HyunJung Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
In the present study, using photothermal effect, the photothermal deflection method is applied to measure the thermal conductivity of bulk and thin film metals. The experimental setup is equipped much more accurately than the previous photothermal deflection methods in the view of optical alignment. The used specimens are the pure and bulk metals with the purity over 99.98%, the thin film metal deposited in fused silica, and the oxide thin film deposited in silicon wafer. The difference of thermal conductivity between thin film and bulk of same material is shown within 2% when the thin film materials are optically thick. When the thin film is optically thin, it is difficult to measure it. However, the thermal conductivity of the p and n type silicon wafer used as the substrate can be measured, which has not existed previously.
윤영선(Youngsun Yun),강준원(Junone Kang),유재석(Jaisuk Yoo),김현정(HyungJung Kim) 한국가시화정보학회 2006 한국가시화정보학회지 Vol.4 No.2
The data for friction factor of the pipe correlated by Reynolds number and relative roughness have been reported well as a Moody chart. However, the results for corrugated shapes have been not investigated sufficiently. In this research, therefore, the pressure drop and friction factor are obtained. Flexible metal tubes with corrugations for the measurement are made of stainless steel plates. The kinds of tubes for the measurement are 5 annular types and helical types. The pressure drop & the velocity of the flow are obtained by micromanometer & digital pressure sensor, supplying dry air at several steps. Then the pressure drop is calculated for each tube, using the obtained data. The result shows that the pressure drop is strongly influenced by the viscous dissipation of kinetic energy due to the circulation of flows, rather than a viscous friction loss. The pressure drop increased consistently as the Reynolds number increases.