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오늘 본 자료
조중원,김상준,안기장,정명균,Cho, Choong-Won,Kim, Sang-Joon,Ahn, Gi-Jang,Chung, Myung-Kyoon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
In the gas wiping process of continuous hot-dip galvanizing, edge overcoating develops near the edge of the steel strip. The overcoating is supposed to occur due to the reduced impact pressure of wiping gas on the strip surface. The purpose of this study is to investigate the effect of edge vortex on the reduced impact pressure. Three-dimensional unsteady flows are simulated using a commercial code, STAR-CD. Standard k-$\varepsilon$ model is used as a turbulence model. It is found that an alternating vortex structure in the vicinity of strip edge is developed by buckling of opposed jet streams and that the reduced amount of impact pressure at strip edge becomes smaller as the air knife gets closer to the strip. The effect of edge baffle on the reduced impact pressure is also investigated.
고분자 전해질 연료전지의 매니폴드 및 분리판 유동분배 특성 분석
조중원(Cho, Chung-Won),유상필(Yoo, Sang-Phil),김민진(Kim, Min-Jin),이원용(Lee, Won-Yong),김창수(Kim, Chang-Su) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11
A numerical study is made of a manifold and bipolar plate in polymer electrolyte fuel cells, the aim of the present study is to describe the characteristics of flow pattern In manifold and bipolar plate. The present work shows that the flow pattern in the bipolar plate is affected by the penetration flow through GDL characterized by clamping pressure and GDL intrusion in to a channel area. Manifold geometry also affects the flow distribution. The recirculation flow by bent duct destroy even distribution In manifold, the present work shows that corner rounding can improve the manifold performance.
가스확산층을 통과하는 반응가스 우회유동이 고분자 연로전지의 성능에 미치는 영향
조중원(Cho, Choong-Won),안은진(Ahn, Eun-Jin),이승보(Lee, Seung-Bo),이원용(Lee, Won-Yong) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11
A serpentine channel geometry often used in a polymer electrolyte membrane fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with relatively high aspect ratio active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compression conditions. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds to that of dropwise condensation in cathode channels.
사행유로를 갖는 고분자연료전지내부에서 가스확산층을 통과하는 반응가스 우회유동에 대한 연구
조중원(Choong-Won Cho),안은진(Eun-Jin Ahn),이승보(Seungbo Lee),윤영기(Young-Gi Yoon),이원용(Won-Yong Lee) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.4
A serpentine channel geometry often used in a fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from the intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with high aspect ratio of active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compressive forces. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds that of dropwise condensation in cathode channels.
조중원(Choong-Won Cho),원종필(Jongphil Won),이호성(Hoseong Lee),이동혁(Donghyuk Lee),오태성(Tae Sung Oh),박용선(Yong Sun Park) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Ethylene glycol is generally mixed with water as antifreezing solution in a thermal management system for a fuel cell vehicle, but there are significant differences between ethylene glycol and water. For example, ethylene glycol has much higher viscosity than that of water. These differences in physical property lead to reduction in heat transfer rate of the thermal management system. this study describes the characteristics of heat transfer in a stack and a radiator respectively, because flows in the stack is laminar. Empirical correlation is used to calculate physical properties of antifreezing coolant. In this study, we show that use of the antifreezing solution causes increase in temperature difference between coolant input and coolant output of the stack. this temperature rise effects the performance of the fuel cell stack.
인버터 스크롤 압축기를 적용한 루프형 전동공조시스템의 냉방성능특성에 관한 연구
이무연(Lee, Moo-Yeon),원종필(Won, Jong-Phil),이동연(Lee, Dong-Yeon),조중원(Cho, Chung-Won) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.10
본 연구에서는 친환경 대형 버스 차량에 적용되는 루프형 전동식 냉방시스템의 성능특성을 파악하기 위하여 스크롤 압축기의 주파수 및 승차 공간의 온도인 내기온도를 변화시켜가면서 다양한 실험을 진행하였다. 이를 위하여 인버터로 구동되는 전동식 스크롤 압축기를 적용한 냉방시스템을 설계 및 제작 하였고 냉매 충진량 실험을 통하여 루프형 전동식 냉방시스템의 충분한 과냉도를 확보할 수 있는 최적 냉매 봉입량을 선정하였다. 압축기 주파수가 55 Hz에서 65 Hz로 증가함에 따라 냉방시스템의 증발용량은 4.3% 증가하였으나 냉방 COP는 14.1% 감소하였고, 내기온 도가 27oC에서 35oC로 증가함에 따라 냉방시스템의 증발용량 및 COP는 각각 9.17%와 1.43% 증가하였다. 더불어 전 동식 스크롤 압축기를 구동하는 인버터의 작동 효율은 내기온도 변화보다는 압축기 주파수 변화에 더 큰 영향을 받 는 것을 확인하였다. The objective of this study is to investigate the cooling performance of the roof mounted air-conditioning system using electric driven scroll compressor for zero emission vehicles. This air conditioner with air source was used R-134a as a refrigerant and tested under various operating conditions such as refrigerant charge amount and indoor temperature, and compressor frequencies. Experimental results revealed that at all tested compressor frequencies, heat transfer rate of the evaporator increased and the cooling COP increased with the indoor temperature. In addition, the heat transfer rate of the evaporator was over 25.0kW sufficient for the cooling loads of an electric bus.