• Title/Summary/Keyword: Reaction Model

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Numerical Study on Operating Parameters and Shapes of a Steam Reformer for Hydrogen Production from Methane (천연가스로부터 수소를 생산하기 위한 수증기 개질기의 작동조건과 형상에 대한 수치해석 연구)

  • Park, Joong-Uen;Lee, Shin-Ku;Lim, Sung-Kwang;Bae, Joong-Myeon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.1
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    • pp.60-68
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    • 2009
  • 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.

A reaction-diffusion modeling of carbonation process in self-compacting concrete

  • Fu, Chuanqing;Ye, Hailong;Jin, Xianyu;Jin, Nanguo;Gong, Lingli
    • Computers and Concrete
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    • v.15 no.5
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    • pp.847-864
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    • 2015
  • In this paper, a reaction-diffusion model of carbonation process in self-compacting concrete (SCC) was realized with a consideration of multi-field couplings. Various effects from environmental conditions, e.g. ambient temperature, relative humidity, carbonation reaction, were incorporated into a numerical simulation proposed by ANSYS. In addition, the carbonation process of SCC was experimentally investigated and compared with a conventionally vibrated concrete (CVC). It is found that SCC has a higher carbonation resistance than CVC with a comparable compressive strength. The numerical solution analysis agrees well with the test results, indicating that the proposed model is appropriate to calculate and predict the carbonation process in SCC. The parameters sensitivity analysis also shows that the carbon dioxide diffusion coefficient and moisture field are essentially crucial to the carbonation process in SCC.

A New Cure Kinetic Model Using Dynamic Differential Scanning Calorimetry (일정온도 상승률 열분석법을 이용한 수지 경화 모델 개발)

  • Eom, Mun-Gwang;Hwang, Byeong-Seon;Isaac M. Daniel
    • 연구논문집
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    • s.29
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    • pp.151-162
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    • 1999
  • In general, manufacturing processes of thermosetting composites consist of mold filling and resin cure. The important parameters used in modeling and designing mold filling are the permeability of the fibrous preform and the viscosity of the resin. To consolidate a composite, resin cure or chemical reaction plays an essential role. Cure kinetics. Therefore, is necessary to quantify the extent of chemical reaction or degree of cure. It is also important to predict resin viscosity which can change due to chemical reaction during mold filling. There exists a heat transfer between the mold and the composite during mold filling and resin cure. Cure kinetics is also used to predict a temperature profile inside composite. In this study, a new scheme which can determine cure kinetics from dynamic temperature scaning was proposed. The method was applied to epoxy resin system and was verified by comparing measurements and predictions.

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A Study on the Relationship among the Concentration of Reacting Air Pollutants in Urban Atmosphere (도시 대기중에서 반응성 대기오염물질의 농도변화 상관성에 관한 연구)

  • Lee, Hwa-Woon;Kim, Yoo-Keun;Jang, Eun-Suk
    • Journal of Environmental Science International
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    • v.6 no.4
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    • pp.351-357
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    • 1997
  • In the Atmosphere under the various physical and chemical condition different chemical reactions occur and there are a number of air pollutants which are generated by photochemical reaction by absorbing solar energy. Therefor various testing simulation was done as foundation work to develop the numerical model for the prediction of concentration of air pollutants. It was shown change of msjor air pollutants concentration In according to variation of photodissociation speed constant, Kl and Initial condition of air pollutants concentration which plays major role In photochemical reaction. The photochemical reaction model which was used In this study Is found to be useful for understanding relationship among the concentration of reacting air pollutants and the prediction of concentration of air pollutants in urban atmosphere.

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Effect of discontinuous mixture gas feeding on effective hydrogen production in a steam reformer frommethane (효율적 수소 생산을 위한 메탄 수증기 개질 반응기에서의 불연속적 가스 유입의 영향)

  • Lee, Shin-Ku;Park, Joon-Guen;Lim, Sung-Kwang;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.10a
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    • pp.25-28
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    • 2008
  • Steam reforming reaction is a matured technology to get hydrogen from hydrocarbon fuels compared with other reforming reactions such as partial oxidation(POX), autothermal reforming(ATR). It is so endothermic that it needs heat source to activate the reaction. Due to the reaction characteristics, heat transfer limitation phenomena generally occur in the steam reformer. As one of new ideas, the effect of discontinuous gas feeding is investigated based on heat transfer characteristics. The new operating method is usually favorable at high GHSV region(i.e. over $10,000h^{-1}$). In order to numerically simulate the physical issues, numerical approach is adopted based on heterogeneous reaction model, two-equation model in energy equation, and other constitutive models in porous media.

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Computer Simulation of Liquid-Fuelled Combustor in Hot Vitiated-Air Stream (고온.저산소 농도영역중의 분무연소해석)

  • 김태한;최병륜
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.3187-3195
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    • 1993
  • Combustion of liquid-fuelled combustion in a high-temperature vitiated-air stream was studied. The mathematical formulation comprise the application of Eulerian conservation equation to the gas phase and Lagrangian equation of droplet motion. The latter is coupled with a droplet-tracking technique (PSI-CELL Model) which regard the droplet phase as a source of mass, momentum, and energy to the gaseous phase. Reaction rate is determined by taking into account the Arrhenius reaction rate based on a single-step reaction mechanism. The calculated profiles show somewhat uncertainess at the upstream, but bases data for designing the combustor followed by 2-phase flow were obtained.

Parameter Estimation in Enzymatic Reaction Model (효소반응 모델식에서의 매개변수 추정)

  • 채희정;김지현차형준유영제
    • KSBB Journal
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    • v.5 no.2
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    • pp.133-139
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    • 1990
  • A simple and convenient method was introduced to determine the kinetic parameters for various enzymatic reaction kinetics. The method based on integrated formular can be applied to the parameter estimations from a single experiment. A modified three-parameter model was applied for the parameter estimation in reversible reaction and the equilibrium substrate concentration could be also estimated. It is possible to identify the enzymatic reaction pattern by inspecting the parameter values and the square of the correlation coefficient.

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A Kinetic Study of Biphenyl Type Epoxy-Xylok Resin System with Different Kinds of Catalysts

  • 한승;김환근;윤호규;문탁진
    • Bulletin of the Korean Chemical Society
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    • v.18 no.11
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    • pp.1199-1203
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    • 1997
  • The investigation of cure kinetics of biphenyl epoxy (4,4-diglycidyloxy-3,3,5,5-tetramethyl biphenyl)-xylok resin system with four different catalysts was performed by differential scanning calorimeter using an isothermal approach. All kinetic parameters of the curing reaction including the reaction order, activation energy and rate constant were calculated and reported. The results indicate that the curing reaction of the formulations using triphenylphosphine (TPP) and 1-benzyl-2-methylimidazole (1B2MI) as a catalyst proceeds through a first order kinetic mechanism, whereas that of the formulations using diazabicyloundecene (DBU) and tetraphenyl phosphonium tetraphenyl borate (TPP-TPB) proceeds by an autocatalytic kinetic mechanism. To describe the cure reaction in the latter stage, we have used the semiempirical relationship proposed by Chern and Poehlein. By combining an nth order kinetic model or an autocatalytic model with a diffusion factor, it is possible to predict the cure kinetics of each catalytic system over the whole range of conversion.

Reaction force of ship stern bearing in hull large deformation based on stochastic theory

  • Zhang, Sheng-dong;Long, Zhi-lin;Yang, Xiu-ying
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.12 no.1
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    • pp.723-732
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    • 2020
  • A theoretical calculation model for ship stern bearings with large hull deformation is established and validated theoretically and experimentally. A hull simulation model is established to calculate hull deformations corresponding to the reaction force of stern bearings under multi-factor and multi-operating conditions. The results show that in the condition of wave load, hull deformation shows randomness; the aft stern tube bearing load obeys the Gaussian distribution and its value increases significantly compared with the load under static, and the probability of aft stern tube bearing load greater than 1 is 65.7%. The influence laws and levels between hull deformation and bearing reaction force are revealed, and suggestions for ship stern bearing specifications are proffered accordingly.

Comparison of Alternate Approaches for Reversible Geminate Recombination

  • Khokhlova, Svetlana S.;Agmon, Noam
    • Bulletin of the Korean Chemical Society
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    • v.33 no.3
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    • pp.1020-1028
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    • 2012
  • This work compares various models for geminate reversible diffusion influenced reactions. The commonly utilized contact reactivity model (an extension of the Collins-Kimball radiation boundary condition) is augmented here by a volume reactivity model, which extends the celebrated Feynman-Kac equation for irreversible depletion within a reaction sphere. We obtain the exact analytic solution in Laplace space for an initially bound pair, which can dissociate, diffuse or undergo "sticky" recombination. We show that the same expression for the binding probability holds also for "mixed" reaction products. Two different derivations are pursued, yielding seemingly different expressions, which nevertheless coincide numerically. These binding probabilities and their Laplace transforms are compared graphically with those from the contact reactivity model and a previously suggested coarse grained approximation. Mathematically, all these Laplace transforms conform to a single generic equation, in which different reactionless Green's functions, g(s), are incorporated. In most of parameter space the sensitivity to g(s) is not large, so that the binding probabilities for the volume and contact reactivity models are rather similar.