• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.63-66
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• 2007

Reformers which produce hydrogen from natural gas are essential for the operation of residential PEM fuel cells. For this purpose, steam-methane reforming reactions with Ni catalysts is primarily utilized. Commercial Ni catalysts are generally made to have porous pellet shapes in which Ni catalyst particles are uniformly dispersed over Alumina support structures. This study numerically investigates the reduction of catalyst effectiveness due to the mass transport resistances posed by porous structures of spherical catalyst pellets. The multi-component diffusion through porous media and the accurate kinetics of reforming reaction is fully considered in the numerical model. The preliminary results on the variation of the effectiveness factor according to different operation conditions are presented, which is planned to be used to develop correlations in future studies.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.749-760
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• 2022

An efficient computational fluid dynamics model was proposed for simulating microchannel-type steam/methane reformers with thin washcoat catalyst layers. In this model, by using the effectiveness factor correlations, the overall reaction rate that occurs in the washcoat catalyst layer could be accurately estimated without performing the detailed calculation of heat transfer, mass transfer, and reforming reactions therein. The accuracy of the proposed model was validated by solving a microchannel-type reformer, once by fully considering the complex steam/methane reforming (SMR) process inside the washcoat layer and again by simplifying the SMR calculation using the effectiveness factor correlations. Finally, parametric studies were conducted to investigate the effects of operating conditions on the SMR performance.

• 신재생에너지
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• 제19권2호
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• pp.1-12
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• 2023

In this study, an efficient one-dimensional model was developed for predicting microchannel steam/methane reformers with thin washcoat catalyst layers with a focus on low-pressure reforming conditions suitable for distributed hydrogen production systems for fuel cell applications. The governing equations for steam/methane mixture gas flowing through the microchannel reformer were derived considering the species conservation with reforming reactions and energy conservation with external convective heat supply. The reaction rates for the developed model were simply determined through the catalyst effectiveness factor correlations instead of performing complicated calculations for the steam/methane reforming process occurring inside the washcoat catalyst layers. The accuracy of the developed was verified by comparing the results obtained herein with those obtained by the detailed computational fluid dynamics calculation for the same microchannel reformer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.514-517
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• 2008

Water gas shift(WGS) is an important step in fuel process for fuel cells, and improperness of commercial WGS catalysts for use in fuel cell systems has prompted numerous researches on noble metal catalysts. A selected noble metal catalyst for water gas shift reaction(WGS) was prepared with various metal loadings. The prepared catalysts were tested under two feeding conditions. At moderate residence time, carbon monoxide conversion was much higher on the noble metal catalysts as compared to commercial high-temperature shift catalyst. Effects of metal loading were examined by activity tests at short residence time. Higher metal loading effected higher reaction rate. The kinetic data was fitted to simple reaction equations and effectiveness factor was estimated. The results suggest the necessity of a structural design for the highly active noble metal catalysts.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.214-223
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• 2002

Kinetic and effectiveness factors for methanol steam reforming using commercial copper-containing catalysts in a plug flow reactor were investigated over the temperature ranges of $180-250^{\circ}C$ at atmospheric pressure. The selectivity of $CO_2$/$H_2$ was almost 100%, and CO products were not observed under reaction conditions employed in this work. It was indicated that $CO_2$ was directly produced and CO was formed via the reverse water gas shift reaction after methanol steam reforming. The intrinsic kinetics for such reactions were well described by the Langmuir-Hinshelwood model based on the dual-site mechanism. The six parameters in this model, including the activation energy of 103kJ/mol, were estimated from diffusion-free data. The significant effect of internal diffusion was observed for temperature higher than $230^{\circ}C$ or particle sizes larger than 0.36mm. In the diflusion-limited case, this model combined with internal effectiveness factors was also found to be good agreement with experimental data.

• 한국가스학회:학술대회논문집
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• 한국가스학회 2007년도 춘계학술발표회 논문집
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• pp.27-32
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• 2007

Dimethyl Ether (DME, $CH_3OCH_3$) is the simplest ether and is considered as one of the leading candidates in the quest for a substitute fur petroleum-based fuels. In this work, we analyzed the one-step synthesis of DME in a shell and tube type fixed bed reactor and carried out a simulation with a one-dimensional, steady state model of a heterogeneous catalyst bed, while taking into consideration the heat and mass transfer between the catalyst pellets and reactants gas and the effectiveness factor of the catalysts, together with the reactor cooling through the reactor tube wall. The reactor simulation was carried out under steady state condition and we compared the simulation results with the experimental data obtained from operations of a pilot-scale reactor and found good agreement between them.

• 전기전자학회논문지
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• 제21권2호
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• pp.123-129
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• 2017

고분자 막 연료전지는 높은 전력밀도, 낮은 배출 및 낮은 동작온도 때문에 미래 자동차 및 전력생산의 강력한 보류이다. FEMFC 내부의 기체확산층(GDL)의 중요한 관심은 물의 조절이다. GDL은 소수성 PTFE와 전기전도성을 위해서 탄소로 보통 구성되어 있다. 이 시뮬레이션에서 GDL 흐름은 확립된 방정식 모델의 단순화된 접근법으로 조사되었다. GDL의 성능은 모델 방정식을 이용하여 전지의 내부열, 수증기 밀도 와 산소밀도의 결과를 보였다. FEMFC 촉매층 모델은 유효인자, Butler-volmer 와 수소유동 밀도의 결과를 나타냈다. 이 결과들은 몇 가지 요소들과 함께 영향의 차이는 흥미 가지게 되며 정보는 연료전지를 설계하는데 도움을 줄 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.230.2-230.2
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• 2010

천연가스 수증기 개질 반응에 사용되는 펠릿 촉매의 단점인 열 및 물질 전달 제한, 낮은 effectiveness factor, 압력강화와 channeling 등의 문제점을 해결 하고자 모노리스 형태의 금속 구조체 촉매를 본 연구에 적용 하였다. Fecralloy 재질의 금속 구조체에 Ni 촉매를 워시코팅 (wash coating) 하여 제조 하였으며, 이를 천연가스 수증기 개질 반응에 적용하여 수소를 생산하였다. 실험 조건으로는 S/C ratio를 3으로 고정하여 온도를 $600^{\circ}C{\sim}800^{\circ}C$로 변화 시켰으며, GHSV $3000{\sim}30000h^{-1}$에서 진행 되었다. 구조체 촉매 코팅에 사용된 Ni 촉매의 BET, TPR, H2-chemisorption, SEM, EDS의 특성분석을 수행 하였다. 온도별 테스트에서 모노리스 형태의 금속 구조체 촉매가 펠릿 형태의 촉매에 비해 우수한 열전달 효과로 인해 낮은 퍼니스 온도와 높은 반응 활성을 나타내었으며, GHSV 변화에 따른 성능평가 결과도 15wt% $Ni/MgAl_2O_4$펠릿 촉매와 비교하여 금속 구조체 촉매가 높은 활성을 보였다.

• Asia Marketing Journal
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• 제16권3호
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• pp.35-56
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• 2014

With rapid change and intensive competition in the global economy, the capability to capture, absorb, develop, and transfer new knowledge is a key organizational success factor. Through effective learning, companies are more likely to develop the innovation, quality, and responsiveness essential to meet the growing expectations of customers and the disruptive threats of competitors and new technologies. In the paper the role of technological innovation and its relationship to organizational learning in managing technology-based new products are examined. Several factors which can influence the rate and effectiveness of organizational learning are identified. Barriers to learning also are discussed. Finally, several managerial implications and propositions for future research on learning and technological innovation are advanced.

• Korean Chemical Engineering Research
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• 제52권3호
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• pp.395-401
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• 2014

본 연구에서는 고온($230{\sim}290^{\circ}C$)의 무촉매 조건에서 이루어지는 팜 지방산 디스틸레이트(PFAD)의 에스테르화 반응에 대해 수학적 모델링을 통해 그 반응 특성을 분석하였다. '무촉매 에스테르화 반응'에 대해 균일계(homogeneous) 2차 가역 반응으로 가정하였고 액상 내에서 동시적, 경쟁적으로 발생하고 있는 물과 메탄올의 증발과 반응을 모두 고려하기 위해 '반응 유효 인자'(reaction effectiveness factor, ${\eta}$)를 도입하였다. 각 반응물 및 생성물의 농도에 대하여 실험을 통해 측정한 값과 반응모델에 의한 예측값 사이의 차이를 최소화하는 반응속도 상수와 물질전달 계수를 구하기 위해 비선형 계획법(nonlinear programming)을 수행하였다. 이를 통해 얻은 반응의 활성화 에너지는 43.98 kJ/mol이다.