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  • 1
    Electronic Resource
    Electronic Resource
    Formulation of Reduced-Order Models for the Dynamic and Stability Analyses of Autothermal Radial Flow Reactors (2003)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 1.2003, 1, A43 
    Details
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Autothermal radial flow reactors typically consist of a reactor setup of multiple catalyst-beds with internal heat exchange. These reactors are widely used because of their high efficiency due to the internal heat exchange, and radial flow arrangements are preferred due to their low pressure drops. Although an efficient multi-functional reactor arrangement, this setup has shown to provide for an additional destabilizing mechanism via the heat feedback. Thus, additional stability considerations are necessary when operating autothermal or non-adiabatic reactors at high conversions. This work proposes the formulation of a simplified model to investigate the effect of the heat transfer feedback on the stability of autothermal radial flow reactors. The present work focuses on a lumping approach to reduce the order of a complex distributed parameter system. The model is complex enough so as to preserve the intricacies of this reactor arrangement, but still yield a tractable dynamic formulation. The industrial ammonia synthesis process has been chosen as a case study to illustrate the proposed methodology. The lumped model predictions are qualitatively compared against numerical simulations of a detailed mathematical model.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/ijcre/vol1/A43
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Convective regimes in reactive fluid media due to the interaction with catalytic surfaces (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 274-284 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reactive fluid media enclosed in a cavity with a catalytic surface are analyzed. Nonisothermal chemical reactions on this surface can lead to convective instabilities. A simplified model is developed by using a low-order truncation of a Fourier-type expansion and employing the Galerkin method. A linear stability analysis is presented and it is shown that, under certain conditions, the marginal curve for the onset of oscillatory instabilities can lie below that for monotonic ones. The stability of the convective modes is studied by nonlinear stability analysis and it is shown how they can evolve into periodic and nonperiodic motion patterns. Numerical results are provided to support and confirm analytical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857443
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Wall-cooled fixed-bed reactors: Parametric sensitivity as a design criterion (1989)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 287-292 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Multitubular reactors of the heat exchanger type are commonly used to carry out highly exothermic reactions. Two of the main goals, when designing this type of reactor, are to guarantee a safe operation and to minimize the reactor length. Therefore, these concepts are used here as criteria for comparing the performance of the three most common cooling-medium flow arrangements. The analysis of the parametric sensitivity behavior, as well as that of some related measures, indicates that, at least from the steady-state standpoint, the cocurrent arrangement should be considered the most attractive alternative.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690350213
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  • 4
    Electronic Resource
    Electronic Resource
    Transport phenomena and kinetics in an extravascular bioartificial pancreas (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2668-2682 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bioartificial pancreas, consisting of immobilized islets encapsulated within hollow fibers, is investigated as an alternative treatment for insulin-dependent diabetes. A mathematical model is developed to determine whether this configuration of the bioartificial pancreas can yield an insulin response to a glucose challenge with the appropriate dynamics in diabetic humans. The model consists of the 2-D mass-conservation equations for glucose and insulin within the hollow fiber and capillaries. The equations contain terms for insulin-production kinetics by porcine islets and glucose-consumption kinetics. The boundary conditions account for transport resistances of the fiber membrane, the tissue surrounding the implant, and a thin film within the capillaries. The equations are coupled to a pharmacokinetic model of the circulatory system. The calculations show that an optimized design with this configuration will be feasible for human use and requires a total volume of 4.6 mL to reach the target insulin concentration in the bloodstream following a glucose challenge. The parameters and processes controlling the system performance are discussed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420928
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    Paper (German National Licenses)
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