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입.출구의 압력조건에 따른 보텍스 튜브의 에너지분리 특성에 관한 실험적 고찰
유갑종,김정수,최인수 대한설비공학회 2001 설비공학 논문집 Vol.13 No.11
The experimental investigation on energy separation in a vortex tube has been carried out to sow the effect of inlet and outlet pressures with various working fluids(air,$O_2,\;and\; CO_2$). Those outlet pressure means cold outlet and hot outlet pressure which were set equally. The results showed that the total enthalpy variation became a maximum when the mass flow rate at the cold outlet was a half of the total mass flow rate in the vortex tube (y=0.5). The total enthalpy variation was quite affected by the pressure difference between the inlet and outlet of vortex tube when the ratio of the inlet pressure to the cold outlet pressure remained constant. Although specific enthalpy differences between the inlet and the outlet (both cold and hot outlet) did not noticeably vary with the pressure difference, the specific enthalpy difference between the inlet and cold outlet was dominantly affected by physical properties of working gases.
저온의 물속에 잠겨있는 수평 평면에 의하여 야기되는 자연대류의 수치해석
유갑종,예용택,권혁용 대한기계학회 1992 대한기계학회논문집 Vol.16 No.6
본 연구에서는 등온 평면의 온도가 0.0.deg. C부터 8.0.deg. C까지, 그리고 주위물의 온 도가 1.0.deg. C부터 10.0.deg. C까지 일 대 상향 및 하향면 주위에서 일어나는 자연대류를 유한 차분법(FDM)으로 수치해석하여 등온면 주위에서 일어나는 유동형태, 속도분포, 평균 Nusselt수를 구하여 유동 및 열전달특성을 구명하였다. The natural convection from upward and downward facing horizontal isothermal plate immersed in water is studied numerically. The temperature of the plate is from 0.0 .deg. C to 8.0 .deg. C and the ambient water temperature is from 1.0 .deg. C to 10.0 .deg. C. Numerical results are presented for the velocity profiles, temperature profiles, local heat transfer coefficients, and average Nusselt numbers over the entire flow fields. Flow patterns are shown in the upward and downward facing surfaces at different ambient water temperatures. For the upward facing surface, there are upflow and unsteady flow. And the regions of the ambient water temperatures which give rise to the upflow are more extensive as the temperatures of the isothermal surface become more distant from the density extremum temperature. For the downward facing surface, only the downflow region is shown. For the upward facing horizontal isothermal surface, the average Nusselt number(= N $u_{1}$$^{*}$) is 28.86(Ra)$^{0.01}$. And for the downward facing surface, the average Nusselt number(= N $u_{2}$$^{*}$) is $C_{2}$(Ra)$^{0.2}$ and the values of $C_{2}$ are enlarged in the range of 0.785 .leq. $C_{2}$ .leq. 1.250 as increasing of the temperatures of the isothermal surface.ace.ace.
상부가 개방된 수직 캐비티내에 장착된 불연속 균일 발열체의 자연대류 냉각
유갑종,추홍록,김병하,최병철,Yu, Gap-Jong,Chu, Hong-Rok,Kim, Byeong-Ha,Choe, Byeong-Cheol 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.1
Natural convection cooling of discrete heaters located in a two-dimensional vertical open top cavity is investigated experimentally. The five discrete heaters with same heat generation are located on the wall of the cavity. The heaters are arranged in two configurations; flush-mounted on a vertical wall and protruding from the wall about 4.5 mm. The materials used for the vertical walls are copper and epoxy-resin, and air is used as the cooling fluid. The temperature and flow fields in the cavity were visualized by means of Mach-Zehnder interferometer and smoke-method. Also, local temperature measurements are made along the vertical wall. Results are obtained for cavity aspect ratios of 4.6, 7.5 and 9.5 and modified Rayleigh numbers ranging from 10$^{3}$ to 10$^{6}$ . Results indicate that the cooling efficiency for the copper wall is superior to that of the epoxy-resin. For the epoxy-resin wall, the protrusion of the heaters plays a role in decreasing the heat transfer performance. The location of maximum temperature is significantly influenced by the wall materials and heater configurations. Correlations relating the Nusselt number to the modified Rayleigh number are proposed.
유갑종,강창수,이충원,엄용균 경북대학교 산업기술연구소 1989 産業技術硏究誌 Vol.17 No.-
In the recent development of internal combustion engine, considerable increase in speed and power has been accomplished. This achievement, however, brought up various problems due to the excessive piston temperature which becomes a crucial factor in engine durability. In this research, temperature distribution in a piston was investigated experimentally and theoretically with varied operation speed in unloaded condition. The method of temperature measuring is L-link system. The theoretical study was carried out by using the finite-element method. A three-dimensional model which simulates a half of piston has been utilized and the surface temperature measured by L-link. System has been used for the theoretical boundary conditions. The results obtained form the analysis of a piston of four-cycle gasoline engine are as follows; The piston temperature increases directly propotional to the engine speed on the thrust plane of piston crown, the temperature in the region closer to inlet valve is found to be higher than that closer to the exhaust valve, and the heating effect by exhaustion and the cooling effect by suction are shown on the iso-thermal line of crown surface. As the thickness of the crown section increased, the degree of symmetry of iso-thermal line about the center-line also increases. The internal and external temperatures of skirt are almost identical, and the temperature decreases away from fro pin-bos. In the case of pin-bos, the temperature of internal is higher than that of external at the lower part, and the temperature decreases along to the pin-perimeter.
유갑종,박철우,장충선,김현우 대한설비공학회 2004 설비공학 논문집 Vol.16 No.8
Heat sink has extended surface area for enhanced heat transfer. The enhanced convection heat transfer has been used widely, such as cooling electronic chips in the electronics industry. Heat sink usually requires an increase in the heat transfer and a decrease in the pressure drop, and must improve the performance in the flow field of industrial plants. In this study, wing fin heat sink was studied and tests were conducted in a rectangular cross sectional channel with wing fin heat sinks. The leading and trailing ends of a wing fin have a sharp edge, simulating the airfoil feature. Empirical correlations have been developed for wing fin heat sink types. And wing fin heat sinks have better cooling performance than elliptic fin and square fin types.