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냉매 대 부동액 판형 열교환기의 증발열전달 특성에 관한 실험적 연구
우형석(Hyoung Suk Woo),안재환(Jae Hwan Ahn),허재혁(Jaehyeok Heo),강훈(Hoon Kang),김용찬(Yongchan Kim) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7
A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. This has a major advantage over a conventional heat exchanger in that the fluids are exposed to a much larger surface area because the fluids spread out over the plates. In this study, the evaporation heat transfer characteristics of a brazed plate heat exchanger was investigated experimentally using antifreeze coolant (ethylene-glycol water) and R134a as the two fluids in a heat exchanger. The effects of refrigerant mass flux were measured by changing coolant temperature, mass flow rate and composition. R134a evaporation heat transfer coefficient of the heat exchanger was calculated using Logarithmic Mean Temperature Difference(LMTD) and Wilson plot method. Experimental results showed that the average vaporization heat transfer coefficient is increased as the refrigerant mass flux increases. The experimental heat transfer coefficients were also compared with pre-studied correlations for evaporation heat transfer coefficients.
이중열원을 이용한 전기자동차용 히트펌프 시스템의 난방 성능 특성에 관한 연구
우형석(Hyoung Suk Woo),안재환(Jae Hwan Ahn),오명수(Myoung Su Oh),강훈(Hoon Kang),김용찬(Yongchan Kim) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.4
An electric vehicle is an environment-friendly automobile which does not emit any tailpipe pollutant. In a conventional vehicle with an internal combustion engine, the internal cabin of the vehicle is usually heated using waste heat from the engine. However, for an electric vehicle, an alternative solution for heating is required because it does not have a combustion engine. Recently, a heat pump system which is widely used for residential heating due to its higher efficiency has been studied for its use as a heating system in electric vehicles. In this study, a heat pump system utilizing air source and waste heat source from electric devices was investigated experimentally. The performance of the heat pump system was measured by varying the mass flow rate ratio. The experimental results show that the heating capacity and COP in the dual heat source heat pump were increased by 20.9% and 8.6%, respectively, from those of the air-source heat pump.
발광 반도체에 관한 연구 : SSD법에 의한 InP 단결정의 생장과 그 특성
鄭重鉉,文東纘,姜鉉植,金根默,禹亨錫 연세대학교 자연과학연구소 1980 學術論文集 Vol.5 No.-
온도구배가 15-20℃/cm이고 생장온도가 850℃-920℃에서 SSD법으로 InP 단결정을 생장시키었으며, 생장속도는 1.7-2.2mm/day이었다. 생장된 결정의 격자상수로는 a_0=5.865±0.004Å을 얻었다. 77˚K에서 Van der Pauw법으로 측정한 전자농도 및 Hall이등도의 값은 각각 7.33×10^15cm^-2 및 2.77×10^4㎠/V-sec이었다. undoped 결정에서 측정한 photoluminescence의 방출스펙트럼에서 현저한 edge emission피이크(1.42eV)와 약한 accept피이크(1.38eV)가 나타나며, 수은 때문에 생기는 1.32eV 피이크는 나타나지 않았다. InP single crystals are grown using SSD method in which grown temperature is as low as 850°~920℃, temperature gradient and growing velocity are 15-20℃/cm and 1.7-2.2mm/day, respectively. The lattice constant of the grown crystal is a_0=5.865±0.004Å. In undoped InP crystal, electron carrier concentration and Hall mobility are measured to be 7.33×10^15cm^-2 and 2.77×10^4㎠/V.sec, by Van der Pauw method at 77°K. Photoluminescence emission spectra of undoped sample shows dominant edge emission peak(1.42eV) and weak acceptor peak (1.38eV) but Hg-peak (1.32eV).
김수홍,천아름,김충기,박동규,권태우,조성진,우형석 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.5
We have fabricated a polymer light-emitting diode (PLED) from a conventional blue-emitting polymer, polyfluorene (PFO), by constructing a multilayer structure with a metal-ion containing water- soluble non-conjugated polymer, polyurethane with Cs+ ions (PU: Cs+), on the top of the PFO. The device with the PU: Cs+ layer shows a maximum luminance of 4900 cd/m2 at an applied voltage of 10 V while the one without the PU: Cs+ layer shows only 2600 cd/m2 at the same applied voltage. We propose that improved device performance with the PU: Cs+ layer is due to not only an effective hole blocking at the polymer-polymer interface but also an increase in electron injection because of Coulomb attraction between the ions and electrons. We will discuss the effect of the multilayer polymer structure in a PLED in terms of the current/voltage characteristics, the luminance, and the quantum efficiency as functions of the applied bias. We have fabricated a polymer light-emitting diode (PLED) from a conventional blue-emitting polymer, polyfluorene (PFO), by constructing a multilayer structure with a metal-ion containing water- soluble non-conjugated polymer, polyurethane with Cs+ ions (PU: Cs+), on the top of the PFO. The device with the PU: Cs+ layer shows a maximum luminance of 4900 cd/m2 at an applied voltage of 10 V while the one without the PU: Cs+ layer shows only 2600 cd/m2 at the same applied voltage. We propose that improved device performance with the PU: Cs+ layer is due to not only an effective hole blocking at the polymer-polymer interface but also an increase in electron injection because of Coulomb attraction between the ions and electrons. We will discuss the effect of the multilayer polymer structure in a PLED in terms of the current/voltage characteristics, the luminance, and the quantum efficiency as functions of the applied bias.
고온조건에서 에어컨 시스템을 이용한 전기자동차 배터리 냉각
오명수(Myoung Su Oh),안재환(Jae Hwan Ahn),우형석(Hyoung Suk Woo),강훈(Hoon Kang),김용찬(Yongchan Kim) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
An electric vehicle is driven by electricity from its battery which releases heat energy. If the battery did not transfer the heat energy to outside efficiently, its temperature would start to increase. When the temperature rises above 60℃, the battery performance will drop off due to chemical breakdown which causes cycle life to decrease. Therefore, a battery cooling system is necessary to have the battery operated in an ideal working temperature range. In this study, the performance of an air-conditioning system that has two evaporators to cool the cabin and the battery down simultaneously was measured by varying the outdoor temperature and the ratio of mass flow rate. The experimental results showed the battery-cooling system could be a reasonable auxiliary cooling system.