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전산유체역학을 이용한 태양열 화학반응기에서의 열전달 특성 해석
고요한(Johan Ko),강경문(Kyung-Mun Kang),서태범(Tae-Beom Seo) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This paper describes the experiment and simulation results of a heat transfer in the SCR (solar chemical reactor). The SCR is installed on the dish type solar collector, Inha Dish-1 in Songdo, Incheon. Dish type solar collector which has operation temperature above 1000℃ is normally classified in high temperature process in solar thermal engineering. With this high operation temperature, convective heat loss, thermal fracture are important features for designing SCR. In this paper, temperature distribution of the SCR is measured and compared with simulation result. SCR is made of SUS304 and the receiver diameter is 10㎝ and 6 sheets of 10㎜ thickness porous metals are laminated inside the receiver. Irradiation from Inha Dish-1 is about 5㎾. Simulation result and measured temperature shows similar inclination through the center line of the SCR.
고요한(Johan Ko),주현철(Hyunchul Ju) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
A three-dimensional, multi-phase and transient model is presented to describe startup processes of polymer electrolyte fuel cells (PEFCs) from subzero temperatures (cold-start). This PEFC cold-start model accounts for ice/frost formation and evolution in the catalyst layer (CL) and gas diffusion layer (GDL), heat and mass transport phenomena with phase transition, electrochemical kinetics, and their mutual interactions. The model is applied to the single straight channel geometry and solved with commercial computational fluid dynamics (CFD) package, Fluent by using user-defined functions (UDF). The model is validated against previous experimental data and further predicts the cold-start performance under various startup conditions(temperature, membrane water content). This model is expected to not only increase the fundamental understanding of the freezing and thawing mechanism but also contribute to develop a effective heat and water management methode during cold-start.
1차원 DMFC 모델을 이용한 메탄올 크로스오버 영향성 연구
고요한(Johan Ko),푸루소타마(Purushothama Chippar),주현철(Hyunchul Ju) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A 1-dimensional numerical simulation model has been developed for a direct methanol fuel cells (DMFCs). The computational domain for this model includes anode gas diffusion layer(GDL), anode catalyst layer, membrane, cathode catalyst layer and cathode gas diffusion layer. The model determines the channel/GDL boundary conditions by considering the stoichiometry ratio and feeding methanol or air concentrations on anode or cathode channel inlets. Using this 1D model, the effects of methanol crossover on cell performance has been studied under the various operating conditions and cell design parameters such as temperature, feed methanol concentration, current density, stoichiometry ratio, and material properties. According to the 1D simulation results, the amount of methanol crossover highly depends on these parameters and considerably alters DMFC performance in terms of DMFC power density and energy efficiency.
Simulation and Validation of Methanol Crossover in DMFCs
고요한(Ko, Johan),주현철(Ju, Hyunchul) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06
In direct methanol fuel cells(DMFCs), it is well known that methanol crossover severely reduces the cell performance and the cell efficiency. There are a number of design and operating parameters that influence the methanol crossover. This indicates that a DMFC demands a high degree of optimization. For the successful design and operation of a DMFC system, a better understanding of methanol crossover phenomena is essential. The main objective of this study is to examine methanol-crossover phenomena in DMFCs. In this study, 1D DMFC model previously developed by Ko et al. is used. The simulation results were compared with methanol-crossover data that were measured by Eccarius et al. The numerical predictions agree well with the methanol crossover data and the model successfully captures key experimental trends.
강경문(Kang, Kyungmun),고요한(Ko, Johan),이기용(Lee, Giyong),주현철(Ju, Hyunchul) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06
In this paper, both theoretical and experimental investigations have been performed to examine the effects of key operating parameters on the cell performance of a DMFCs (i.e., methanol feed concentration and operating temperature). For experiment, the membrane electrode assemblies (MEAs) were prepared using a conventional MEA fabrication method based on a catalyst coated electrode (CCE) and tested under various cell temperatures and methanol feed concentrations. The polarization curve measurements were conducted using in-house-made 25cm² MEAs. The voltage-current density data were collected under three different cell temperatures (50?C, 60?C, and 70?C) and four different methanol feed concentrations (1 M, 2 M, 3 M, and 4 M). The experimental data indicate that the measured I-V curves are significantly altered, depending on these conditions. On the other hand, previously developed one-dimensional, two-phase DMFC model is simulated under the same operating conditions used in the experiments. The model predictions compare well with the experimental data over a wide range of these operating conditions, which demonstrates the validity and accuracy of the present DMFC model. Furthermore, both simulation and experimental results exhibit the strong influences of methanol and water crossover rates through the membrane on DMFC performance and I-V curve characteristics.
One-dimensional, Transient DMFC Modeling and Simulations
푸루소타마(Purushothama Chippar),고요한(Johan Ko),주현철(Hyunchul Ju) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A one dimensional two phase, multi-component, transient DMFC model has been developed to investigate transient and thermal behaviors of DMFCs as well as the detailed species transport, methanol crossover, stoichiometric ratio effects on cell performance. The present 1D model considers transport processes through the cell thickness and thereby consists of three DMFC segments namely, anode backing layer, cathode backing layer and membrane with an assumption that catalyst layers are infinitely thin interfaces between backing layers and membrane. Stefan-Maxwell multi-component diffusion equation is employed to formulate methanol and water transport through porous media, while Darcy's law is used to describe liquid flow due to capillary action. The 1D transient DMFC model successfully captures the coupled thermal and transient behaviors of DMFC under various operating conditions and cell designs, which indicates that the present 1D DMFC model is a useful tool in optimizing cell operating conditions and material/design parameters.