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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.
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.
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.
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.
공기열원 히트펌프 시스템 실내 응축기 성능 특성에 관한 실험적 연구
이호성(Ho-seong Lee),원종필(Jong-phil Won),조중원(Choong-won Cho),장영기(Young-ki Chang),임택규(Taek-kyu Lim),전한별(Han-byoel Jeon),김용찬(Yong-chan Kim) 한국산학기술학회 2014 한국산학기술학회 학술대회 Vol.- No.-
The development of eco-friendly cars due to global warming. The main problem is the relatively short when compared to the existing mileage per charge of the electric vehicle is a problem. In this situation, because the electrical energy must be spent for heating electric vehicles reduced mileage per charge. Heating performance is studied for air heat source heat pump system. In this study, experiment to analyze heating performance characteristics with air heat source have been with various operating conditions, which are likely to match the air heat source Heat pump system operating conditions under cold ambient conditions, such as variation of compressor speed and interior air temperature. Ambient temperature down from 5℃ to –10℃ occurs reduction of heating capacity of inner condenser due to reduction of refrigerant flow rate in accordance with reduction of 45% density of refrigerant. Increasing compressor speed from 2000 RPM to 3,500 RPM occurs increasing of heating capacity of inner condenser. But COP of heat pump system is reduced 26% due to additional compressor power. It seems a good way to study for a plan to try to increase inner condenser air flow rate, inner heat exchanger area.
자동차용 CO₂ 에어컨 시스템 성능향상에 관한 실험적 연구
김성철(Sung Chul Kim),원종필(Jong Phil Won),이동혁(Dong Hyuk Lee),이호성(Ho Seong Lee),조중원(Choong Won Cho),정정훈(Jung Hun Jung) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
This paper investigated the performance characteristics of a CO₂ air conditioning system for vehicles. We has developed the air conditioning system using CO₂ as a working fluid and improved the system performance by modifying the main components. The results of cooling experiments for steady state performance are provided for various operating conditions, which are quite matching the actual vehicle's driving conditions such as different compressor speeds and evaporator/gas cooler air inlet temperatures. The experimental data show that the cooling capacity and coefficient of performance (COP) were up to 5.5 ㎾ and 2.3, respectively, at standard test condition. Therefore, we concluded that the mobile air conditioning system using CO₂ has the good performance level.
기체확산층 투과도에 따른 고분자전해질연료전지의 성능에 관한 수치적 연구
김경연(Kyoungyoun Kim),손영준(Young-Jun Sohn),김민진(Minjin Kim),조중원(Choong-Won Cho),이원용(Won-Yong Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The serpentine channel widely employed in fuel cells has a strong pressure gradient between adjacent channels in specific regions. Due to the pressure gradient, some amount of reactant gas can be delivered to a catalyst layer by convection as well as diffusion processes in a gas diffusion layer (GDL). The enhancement of the convective flow, so-called bypass flow affects performance of a PEMFC since the bypass flow can lead to significant concentration loss at the downstream of the gas channel. By performing three-dimensional numerical simulation, we have investigated the bypass flow in the GDL and its effects on the distribution of reactant concentration and local current density. The present numerical results show that, with increasing GDL permeability, local current density distribution changes significantly and becomes more inhomogeneous.
100kW급 연료전지 열관리 시스템 실도로 운전조건 해석적 연구
이호성(Ho-Seong Lee),이무연(Moo-Yeon Lee),조중원(Choong-Won Cho) 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.2
본 연구의 목적은 100kW급 연료전지 시스템의 열관리 성능을 실도로 운전조건에서 분석하여, 성능 해석 모델링을 개발하는 것이다. 개발된 모델을 적용하여, 열관리 시스템의 운전조건 변화에 따른 성능 변화를 고찰하고자 한다. 해석 모델링은 핵심부품들에 대한 성능 평가 데이터를 바탕으로, 성능에 영향을 주는 변수들로 개발하였다. 개발된 연료전지 열관리 시스템 해석 모델링으로 다양한 실차 운전조건에서의 최적 열관리 시스템에 대한 전력소비량을 분석하였다. 주요하게, 연료전지 열관리시스템 핵심부품(워터펌프, 냉각 팬, 3 Way Valve, 라디에이터)에 대한 성능 특성 분석 후 모델링을 진행하였다. 개발된 모델링으로 운전조건에 따른 유량 예측을 하였고, 실험값과 예측값과의 비교분석을 통하여서, 해석 모델링에 대한 검증을 진행하였다. 과도해석을 통하여서, 냉시동시 냉각수 온도가 특정온도까지의 소요시간을 예측하였다. 스택 운전조건에서 스택 입출구 온도가 적정 수준에서 움직이기 위한 열관리 시스템 운전조건에 대한 예측을 진행하였다. 그 결과를 바탕으로, 소모전력과 열방출량과의 비교분석을 하였다. 개발된 해석 모델링은 핵심부품들의 성능 변화시 연료전지 시스템 운전에 대한 영향도를 분석할 수 있도록 활용할 예정이다. The objective of this study was to investigate performance characteristics of thermal management system(TMS) in a fuel cell electric vehicle with 100kW Fuel Cell(FC) system. In order to build up analytic modeling for TMS, each component was installed and tested under various operating conditions, such as water pump, radiator, 3-Way valve, COD heater, and FC stack etc. and as the results of them, correlations reflecting component’s characteristics with flow rate, air velocity were developed. Developed analytic modelling was carried out under various operating conditions on the road. To verify modelling’s accuracy, after prediction for optimum coolant flow rate was fulfilled under certain operating conditions, such as FC system, water pump speed, opening of 3-way valve, and pipe resistance, analytic and experimental values were compared and good agreement was shown. In order to predict cold-start operating performance for analytic modelling, coolant temperature variation was analyzed with –20℃ ambient temperature and duration was predicted to rise in optimum temperature for FC. Because there is appropriate temperature difference between inlet and outlet of FC stack to operate FC system properly, related analysis was performed with respect to power consumption for TMS and heat rejection rate and performance map was depicted along with FC operating conditions.