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정혜미(JUNG, Hye-Mi),엄석기(UM, Sukkee),박정선(PARK, Jungsun),이원용(LEE, Won-Yong),김창수(KIM, Chang-Soo) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
The effects of internal manifold designs the reactant feed-stream in Polymer Electrolyte Fuel Cells (PEFCs) is studied to figure out mass flow-distribution patterns over an entire fuel cell stack domain. Reactants flows are modeled either laminar or turbulent depending on regions and the open channels in the bipolar plates are simulated by porous media where permeability should be pre-determined for computational analysis. In this work, numerical models for reactant feed-stream in the PEFC manifolds are classified into two major flow patterns: Z-shape and U-shape. Several types of manifold geometries are analyzed to find the optimal manifold configurations. The effect of heat generation in PEFC on the flow distribution is also investigated applying a simplified heat transfer model in the stack level (i.e. multi-cell electrochemical power-generation unit). This modeling technique is well suited for many large scale problems and this scheme can be used not only to account for the manifold flow pattern but also to obtain information on the optimal design and operation of a PEMC system.
고분자 전해질 연료전지 매니폴드의 열유동 특성에 관한 수치적 연구
정혜미(Jung, Hye-Mi),엄석기(Um, Sukkee),손영준(Sohn, Young-Jun),박정선(Park, Jungsun),이원용(Lee, Won-Yong),김창수(Kim, Chang-Soo) 한국신재생에너지학회 2005 신재생에너지 Vol.1 No.2
The effects of internal manifold designs on the reactants feed-stream in Polymer Electrolyte Fuel Cells [PEFCs] is studied to figure out flow and thermal distribution patterns over an entire fuel cell stack. Reactants flows are modeled either laminar of turbulent depending on regions and the open channels in the bipolar plates are simulated by porous media where permeability should be pre-deter-mined for computational analysis. In this work, numerical models for reactants feed-stream In the PEFC manifolds are classified Into two major flow patterns: Z-shape and U-shape. Several types of manifold geometries are analyzed to find the optimal manifold configurations. The effect of heat generation in PEFC on the flow distribution is also Investigated applying a simplified heat transfer model in the stack level (i.e. multi-cell electrochemical power-generation unit). This modeling technique Is well suited for many large scale problems and this scheme can be used not only to account for the manifold flow pattern but also to obtain Information on the optimal design and operation of PEFC systems.
리튬이온 전지의 내압변화 원인과 안전변의 작동압 피로 시험
김용삼(Yongsam Kim),엄석기(Sukkee Um) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Inner pressure of Li-ion battery is easily changed by temperature, battery SOC %, storage time and side reaction. Gas evolution by side reaction is main factor for inner pressure increase but the mechanism was not clearly defined. So inner pressure of Li-ion battery was directly measured during cycling and storage. Through this measurement it was found that maximum cell inner pressure came from high temperature storage by side reaction. General Li-ion battery has a vent of safety device for gas exhausting. It was predicted that vent is very weak for repeated inner pressure change because vent material is aluminum and vent is very thin. So vent fatigue test was done for operation reliability during life. The degradation of vent operation pressure by repeated inner pressure change was fount but it was not critical to vent operation.
고속ㆍ저토크용 표면부착형 영구자석 동기 전동기의 운전 안정성 확보를 위한 손실 및 열전달 특성 분석
최문석(Moon Suk Choi),엄석기(Sukkee Um) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.3
고속 저토크 표면 부착 영구자석형 동기 전동기의 운전 안정성 확보를 위하여 과속도 및 과부하 영역에서 전동기 코일 온도 예측이 필수적이다. 0.35mm 의 S18, S08 등급인 35PN440, 35PN220 그리고 0.15mm 의 저손실 재료인 15HTH1000 으로 제작된 고정자 철심을 포함하는 전동기의 정격 구동 조건에서 손실 및 코일 온도를 측정하여 과속도 및 과부하 영역의 손실 및 열저항을 예측하고 열전달 모델링을 수행하였다. 이의 검증을 위하여 무부하 과속도 영역에서 계산된 코일 온도와 실험값을 비교하여 6.4%이하로 일치하였다. 35PN440 을 적용한 전동기에 비하여 15HTH100 을 적용한 전동기는 무차원 회전속도 0.9, 부하율 3.0 일 때 철손실이 84.4% 로 감소하였고, 무차원 코일 온도 1.0 을 기준으로 출력이 85.2% 향상되었다. 정격 구동 영역의 손실 측정 및 열전달 모델링으로 과부하 및 과속도 영역에서 철심 재질에 따른 코일 온도 변화 및 전동기 출력 개선량을 정확하게 예측할 수 있음을 알 수 있다. It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.
Backward Energy Flow Management Scheme을 이용한 주택용 연료전지 열병합 발전시스템 통합 시뮬레이션 연구
공낙원(Nak-won Kong),엄석기(Sukkee Um),유상필(Sangphil Yu),김민진(Minjin Kim),이진호(Jinho Lee),이원용(Won-Yong Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Operational strategy for a CHP system has a strong effect on the performance of polymer electrolyte fuel cells (PEFCs)/battery hybrid system. The performance of the integrated CHP system also depends on the efficiencies of fuel cells and peripheral components. In this study, the PEFC/battery hybrid system are laid out for the electrical load, while the thermal storage tank and additional boiler are assumed for the thermal load. Steam methanol reforming systems are configured to simulate hydrogen extraction process, followed by water gas shift reactor and PROX to improve the quality of hydrogen. Considering the systematic efficiencies of every flow processes and seasonal variations of CHP loads, backward energy flow management schemes are developed using MATLAB for the integrated CHP systems.
열 사상법을 이용한 유도 기동형 동기 전동기의 비정상 3차원 열해석
김치원(Chiwon Kim),엄석기(Sukkee Um) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
This paper describes thermal modeling of a line start permanent magnet (LSPM) motor using a computational flow dynamics method. First, 2-dimensional electromagnetic design is carried out in order to comprehend heat losses at winding, stator, rotor and cage. New coupling method called Heat mapping method (HMM) will be introduced which converts 2-D information of electromagnetic domain to 3-D information of thermal domain. Transient thermal analysis under rated operating conditions is performed to identify the load saturation time and temperatures in the LSPM motor. Experimental results are collected under the same operating conditions and computational results are verified against the experimental data. Finally, thermal path analysis at a steady-state is conducted to figure out the direction and magnitude of heat flux in the LSPM motor. These results can be useful to design effective cooling systems of electrical motors.