고체산화물 연료전지를 위한 물성치 및 전기화학반응의 수치해석 모델링

박준근(Joonguen Park),김선영(Sunyoung Kim),배중면(Joongmyeon Bae) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Both physical property based on the ceramic material and electrochemical reaction must be considered for the numerical analysis of the Solid Oxide Fuel Cell (SOFC). In this presentation, detailed models for the SOFC simulation are suggested and the numerical results are compared with the experimental results for the validation. Koide's model is applied for the exchange current density of the anode, and Costamagna's model is used to describe the exchange current density of the cathode. Kilner's model is incorporated for the ionic conductivity of the electrolyte and the value of the ionic conductivity is compared with Kwon's experimental data. Both binary and Knudsen diffusivity are considered to cater for gas diffusion inside the channel and the porous electrode. Activation polarization is calculated using Chan's model. Ohmic polarization is evaluated introducing the ionic and the electronic conductivity as the material properties.

금속지지체형 고체산화물연료전지와 연료극지지체형 고체산화물연료전지의 물질전달 특성분석

박준근(Joonguen Park),김선영(Sunyoung Kim),배중면(Joongmyeon Bae) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.3

고체산화물연료전지의 상용화를 위해서 금속지지체형 고체산화물연료전지가 개발되었다. 이 연료전지는 기계적강도를 향상시킨 새로운 개념의 연료전지지만 접합층으로 인해 물질전달률이 감소한다. 본 논문에서는 전산해석을 이용하여 연료극지지체형 고체산화물연료전지와 금속지지체형 고체산화물연료전지의 물질전달율을 비교하고자 한다. 지배방정식, 전기화학반응, 세라믹 물성치 모델이 동시에 해석된다. 그리고 다공성 매질 내부의 물질전달 해석을 위해서 분자확산과 누센확산이 함께 고려된다. 전산해석의 검증을 위해서 실험결과와 해석결괴를 비교한다. 금속지지체형 고체산화물 연료전지의 평균 전류밀도가 연료극지지체형 고체산화물연료전지에 비해 약 23% 감소한다. 그러나 접합층으로 인해 금속지지체형 고체산화물연료전지가 더 균일한 전류밀도 분포를 가진다. Metal-supported solid oxide fuel cells (SOFCs) have been developed to commercialize SOFCs. This new type of SOFC has high mechanical strength, but its mass transfer rate may be low due to the presence of a contact layer. In this study, the mass transfer characteristics of an anode-supported SOFC and a metal-supported SOFC are studied by performing numerical simulation. Governing equations, electrochemical reactions, and ceramic physical-property models are determined simultaneously; molecular diffusion and Knudsen diffusion are considered in mass transport analysis of porous media. The experimental results are compared with simulation data to validate the results of numerical simulation. The average current density of the metal-supported SOFC is 23% lower than that of the anode-supported SOFC. However, because of the presence of the contact layer, the metal-supported SOFC has a more uniform distribution than the anode-supported SOFC.

금속지지체형 고체산화물연료전지의 스택 매니폴드 구조에 의한 열 및 물질전달 연구

박준근(Joonguen Park),배중면(Joongmyeon Bae) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5

본 논문에서는 연료전지 스택에 수소 및 산소를 공급하기 위한 매니폴드를 설계하고 매니폴드 구조에 따른 열 및 물질전달 변화를 분석하고자 한다. 전기화학반응식, 물성식, 지배방정식을 통합한 전산해석 코드를 개발하고, 단전지의 전류밀도 분포 및 온도분포를 해석한다. 6장의 단전지가 적층된 스택을 설계하고 매니폴드 구조를 변화시킨다. 병렬구조, 직렬구조, 확장구조, 축소구조를 비교한 결과 병렬구조가 가장 균일한 전류밀도 분포를 가지고 압력강하도 가장 작다. 직렬구조는 온도 및 전류밀도 분포 차이가 크고 차압이 병렬구조의 50 배 이상 발생한다. In this paper, the manifold design in order to supply hydrogen and oxygen to fuel cell stacks is studied and heat and mass transfer according to the manifold design is investigated. The numerical simulation code which incorporates electrochemical reactions, physical property equations and governing equations is developed. And then, the single cell is analyzed to present the current density and temperature distribution. The stack which laminates 6 single cells is designed and the manifold shapes are changed. Parallel type, serpentine type, spread out type and taper off type are compared with each other. The parallel type has the most regular current density distribution and the lowest pressure drop. The pressure drop of serpentine type is 50 times bigger than that of parallel type and the serpentine type has the largest difference in the current density and temperature distribution.

천연가스 자열개질기를 위한 작동조건과 개질효율의 상관관계에 대한 수치해석 연구

박준근(Joonguen Park),이신구(Shinku Lee),임성광(Sungkwang Lim),배중면(Joongmyeon Bae) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.8

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

수소 생산을 위한 동축원통형 수증기 개질기의 성능 및 열유속에 대한 수치해석 연구

박준근(Joonguen Park),이신구(Shinku Lee),배중면(Joongmyeon Bae),김명준(Myoungjun Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.9

Heat transfer rate is a very important factor for the performance of a steam reformer because a steam reforming reaction is an endothermic reaction. Coaxial cylindrical reactor is the reactor design which can improve the heat transfer rate. Temperature, fuel conversion and heat flux in the coaxial cylindrical steam reformer are studied in this paper using numerical method under various operating conditions. Langmuir-Hinshelwood model and pseudo-homogeneous model are incorporated for the catalytic surface reaction. Dominant chemical reactions are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming (DSR) reaction. Although coaxial cylindrical steam reformer uses 33% less amount of catalyst than cylindrical steam reformer, its fuel conversion is increased 10 % more and its temperature is also high as about 30 degree. There is no heat transfer limitation near the inlet area at coaxial-type reactor. However, pressure drop of the coaxial cylindrical reactor is 10 times higher than that of cylindrical reactor. Operating parameters of coaxial cylindrical steam reformer are the wall temperature, the inlet temperature, and the Gas Hourly Space Velocity (GHSV). When the wall temperature is high, the temperature and the fuel conversion are increased due to the high heat transfer rate. The fuel conversion rate is increased with the high inlet temperature. However, temperature drop clearly occurs near the inlet area since an endothermic reaction is active due to the high inlet temperature. When GHSV is increased, the fuel conversion is decreased because of the heat transfer limitation and short residence time.

금속지지체형 고체 산화물 연료전지를 위한 유로설계

박준근(Joonguen Park),김선영(Sunyoung Kim),배중면(Joongmyeon Bae) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

For commercialization of solid oxide fuel cells, its strength needs to be improved because ceramic materials have a low strength. Thus, metal-supported SOFCs have been developed as a new concept of SOFC. However, the mass transfer rate in this type of SOFC may be decreased due to the contact layer and the support layer and that can cause the low performance. Therefore, the channel shape for the reactant supplement has to be designed for the high mass transfer rate. In this paper, governing equations, physical property equations, and electrochemical equations are calculated simultaneously. And the numerical results are compared with the experimental results for the code validation. The effects of the channel width, the rig width, and the inlet position are investigated. The current density, temperature, and pressure drop are suggested as numerical results.

고체 산화물 연료전지를 위한 물성치 및 전기화학반응의 수치해석 모델링

박준근(Joonguen Park),김선영(Sunyoung Kim),배중면(Joongmyeon Bae) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.2

고체산화물연료전지는 세라믹 물질로 이루어지며, 세라믹 물질의 물성치는 작동조건에 따라 달라진다. 따라서, 높은 신뢰성을 가지는 시뮬레이션 모델을 개발하기 위해서는 세라믹 물질의 물성치를 정확하게 예측할 수 있어야한다. 본 논문에서는 고체산화물연료전지의 성능에 영향을 미치는 여러가지 물성치를 선택하고 그 물성치를 위한 시뮬레이션 모델이 개발되었다. 개회로전압을 위한 깁스에너지, 활성화손실을 위한 교환전류밀도, 저항손실을 위한 전기전도도가 계산되었다. 또한, 다공성 전극 내부의 물질전달 해석을 위해서 분자확산과 누센확산을 함께 고려하는 유효확산계수가 계산되었다. 이러한 계산과정 후에 물성치 모델과 전기화학반응 모델이 동시에 시뮬레이션 되었다. 해석코드의 검증을 위해서 전산해석 결과는 실험결과 및 Chan 등에 의해서 수행된 이전 연구결과와 비교되었다. Solid oxide fuel cells (SOFCs) are commonly composed of ceramic compartments, and it is known that the physical properties of the ceramic materials can be changed according to the operating temperature. Thus, the physical properties of the ceramic materials have to be properly predicted to develop a highly reliable simulation model. In this study, several physical properties that can affect the performance of SOFCs were selected, and simulation models for those physical properties were developed using our own code. The Gibbs free energy for the open circuit voltage, exchange current densities for the activation polarization, and electrical conductivity for the electrolyte were calculated. In addition, the diffusion coefficient?including the binary and Knudsen diffusion mechanisms?was calculated for mass transport analysis at the porous electrode. The physical property and electrochemical reaction models were then simulated simultaneously. The numerical results were compared with the experimental results and previous works studied by Chan et al. for code validation.

천연가스로부터 수소를 생산하기 위한 수증기 개질기의 작동조건과 형상에 대한 수치해석 연구

박준근(Joonguen Park),이신구(Shinku Lee),임성광(Sungkwang Lim),배중면(Joongmyeon Bae) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.1

The steam reformer for hydrogen production from methane is studied by a numerical method. Langmuir-Hinshelwood model is incorporated for catalytic surface reactions, and the pseudo-homogeneous model is used to take into account local equilibrium phenomena between a catalyst and bulk gas. Dominant chemical reactions are Steam Reforming (SR) reaction, Water-Gas Shift (WGS) reaction, and Direct Steam Reforming (DSR) reaction. The numerical results are validated with experimental results at the same operating conditions. Using the validated code, parametric study has been numerically performed in view of the steam reformer performance. As increasing a wall temperature, the fuel conversion increases due to the high heat transfer rate. When Steam to Carbon Ratio (SCR) increases, the concentration of carbon monoxide decreases since WGS reaction becomes more active. When increasing Gas Hourly Space Velocity (GHSV), the fuel conversion decreases due to the heat transfer limitation and the low residence time. The reactor shape effects are also investigated. The length and radius of cylindrical reactors are changed at the same catalyst volume. The longer steam reformer is, the better steam reformer performs. However, system energy efficiency decreases due to the large pressure drop.