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- 저자 : 차경옥(K.O. Cha) (검색결과 84 건)
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방형파펄즈가열법에 의한 세라믹스의 열물성 측정에 관한 연구
차경옥,이경희,임굉,Cha, K.O.,Lee, K.H.,Yim, Going 한국결정성장학회 1999 韓國結晶成長學會誌 Vol.9 No.6
본 연구에서는 방형파 펄즈 가열법을 이용하여 세라믹 고유전체 열물성치의 측정에 활용하는 것에 대한 가능성을 검토하였다. 여기서 측정의 이론을 설정하고 측정의 자동화를 시도함으로써 매우 짧은 시간내 시료의 열확산계수, 비열 및 열전도율을 얻을 수 있었다. 또한 시료는 실온으로부터 약 1300 K 온도 범위까지 측정하였다. Thermophysical properties of the high-dielectric ceramics were measured by a single rectangular pulse heating method. The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature ranging from room temperature to 1300 K.
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[論文] 方形波 펄스 加熱에 의한 BaOTiO₂,SrOTiO₂,MgOTiO₂系列의 熱物性値 測定에 관한 硏究
차경옥(K. O. Cha),장희석(H. S. Chang),이흥주(H. J. Lee) 한국자동차공학회 1991 오토저널 Vol.13 No.2
In this study, thermophysical properties of the ceramic dielectrics such as BaOTi0₂, SrOTi0₂, MgOTi0₂, were measured by a single rectangular pulse heating method.The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature range from room temperature to 1300k. The measured thermal properties of one group of ceramic material were compared with those of other group and discussed in detail in connection with the chemical composition. Thus, some criteria for thermal design with the electric-electronic ceramic material were proposed.
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차경옥(K. O. Cha),김재근(J. G. Kim) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.1
Many investigations have been made to determine the pressure drop and heat transfer characteristics for single phase flow in tape generated swirl flow. But few studies have been carried out to investigate the heat transfer in two component, two phase swirl flow with non-boiling. An experimental study has been conducted to determine the effects of tape twist ratios on two phase convective heat transfer coefficients, pressure drop, and void fraction distribution in a non-boiling, air-water, two phase flow. The flow conditions were both swirl and non swirl flows. The internal diameter of the test section is 42.5mm. The tape twist ratios of pitch to diameter ratio varied from 4.0 to 10.6. The superficial water and air velocity were controlled from 0.25 to 1.0m/s and 0.5 to 4.0m/s respectively. The heating conditions were isothermal and nonisothermal. The flow patterns identified with experiments were bubbly, bubbly-slug, slug, and slug-annular flow in up-flow.<br/> This study has concluded that no significant difference in void fraction distribution were observed both isothermal and nonisothermal conditions, the pressure drop for two phase flow with twisted tape swirler increase as the tape twist ratio decrease, and that values of two phase heat transfer coefficient increase when the tape twist ratio decreases.
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차경옥(K.O.Cha),김재근(J.G.Kim),유병구(B.G.Yu),양희준(H.J.Yong) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_2
The phenomena of drag reduction to decrease the friction in turbulent flow with small quantities of a linear macromolecules has attracted the attention of many experimental and theoretical investigations. On the other hand drag reduction in two phase flow can be applied to oil transport of crude oil. phase change system such as chemical reactor, pool and boiling flow. and to present cavitation which occurs pump impellers. But the research of drag reduction in two phase flow is not sufficient The purpose of the present work is to evaluate the drag reduction by measuring pressure drop. void fraction, mean liquid velocity and turbulent intensity whether polymer additives a horizontal two phase system or not. Flow pattern of air-water two phase flow was classified by electrical conductivity probe signal. Velocities and turbulent intensities of signal were measured simultaneously with a Hot-film Anemometer.<br/>
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차경옥(K. O. Cha),이준서(J. S. Lee),김형섭(H. S. Kim) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.4
Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clar-ified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is gen-erated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experi-mental model and analysis method which are applied two-port network analysis. Also, it shows co-herence function, frequency response function, back pressure, and gradient of temperature in ex-haust system.<br/>
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차경옥(K. O. Cha),김재근(J. G. Kim) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.3
The phenomena of drag reduction using small quantities of a liner macromolecules has attracted the attention of many experimental investigations. On the other hand drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. But the research on drag reduction in two phase flow is not sufficient. The purpose of the present work is to evalu-ate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity and turbu-lent intensity whether polymer additives a horiwntal single and two phase system or not. Flow pattern of air-water two phase flow was classified by electrical conductivity probe signal. Velocia-ties and turbulent intensities of signal were measured simultaneously with a Hot-film anemome-ter.<br/>
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