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  • 1
    Electronic Resource
    Electronic Resource
    Theory of gas diffusion and permeation in inorganic molecular-sieve membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 58-67 
    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: Theoretical models of gas diffusion and permeation in microporous molecularsieve membranes are presented. The effect of the adsorbed diffusant on the total transmembrane flow is insignificant for permanent gases. For highly adsorbable gases the effect of the adsorbed molecules on the total transmembrane flux may be high at low temperatures. The activation energy of diffusion increases when the kinetic diameter of the diffusant increases. The activation energy of gas diffusion compares well with the values calculated based on the Lennard-Jones potential. Maximum possible permeability coefficients calculated for He in the molecular-sieve membranes do not exceed ˜30,000 Barrer at room temperature. The experimentally observed value for He permeability is ˜1,000 Barrer (T=30°C) because of the high tortuosity (τ≍ 25) and low porosity (θ = 0.22) of the membrane porous structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410107
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  • 2
    Electronic Resource
    Electronic Resource
    Strategy for dynamic process modeling based on neural networks in macroscopic balances (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3403-3418 
    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: Gray box models combine the short development time of data-driven black box models with extrapolation properties of knowledge-driven first principles models (white box), which in (bio)chemical engineering are always based on macroscopic balances. By modeling the inaccurately known terms in a macroscopic balance with a black box model, one naturally obtains a so-called serial gray box model configuration. The identification data must cover only the input-output space of the inaccurately known terms, and the accurately known terms can be used for reliable extrapolation. In this way, the serial gray box configuration results in accurate models with known extrapolation properties with a limited experimental effort. This strategy is demonstrated for the modeling and control of a pressure vessel using real-time experiments. For this case, the strategy is superior to a black box modeling approach that requires much more data and to a parallel gray box approach that results in a model with poor extrapolation properties. Moreover, neural networks are an accurate and convenient modeling tool for the black part in gray box model configurations, because a very fast noniterative training algorithm is used for training neural networks.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421211
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  • 3
    Electronic Resource
    Electronic Resource
    Transient free-surface flows: Fluid advancing through a bed of cylinders (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1894-1902 
    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: The flow of a viscous liquid into a bed filled with a regular array of cylinders was observed experimentally and simulated numerically. Viscous forces were always dominant, as is expected to be the case in many actual resin transfer molding operations.Excellent agreement on the shape of the free surface was found between experiment and simulation over the full experimental range. The work accordingly validates a very simple algorithm for representing the surface motion of a fluid at its contact line with a solid surface, and extends its use to surfaces with smaller radii of curvature than considered previously. Consequently, this algorithm is expected to be valid for fluid flow into any irregularly shaped empty domain and to be useful in molding operations in inferring the presence of voiding, and of molecular orientations and conformations adjacent to fibers or other solids.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690341115
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  • 4
    Electronic Resource
    Electronic Resource
    Transient free-surface flows: Motion of a fluid advancing in a tube (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1178-1186 
    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: The fluid motion at a free surface advancing into a mold or duct is appreciably different from its steady state behavior in well-developed flow; this affects the residence time distribution and structure of macromolecular fluids as they are frozen in injection molding processes. In this work such motion is treated numerically and measured precisely for Newtonian fluids. While the three-phase contact line represents a special problem conceptually and analytically, a very simple algorithm is seen to represent the fluid motion in this region accurately.Good agreement is found over wide ranges of the governing dimensionless groups (the Reynolds, Jeffrey, and capillary numbers). Since viscous forces are dominant under the circumstances studied, this finding is not surprising but it confirms the applicability of the numerical methods developed herein to the modeling of these flows under conditions of actual interest. As a result, simulations may be made with confidence to predict flow patterns encountered in practice but difficult to reproduce in laboratory experiments.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330712
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  • 5
    Electronic Resource
    Electronic Resource
    Heat transfer to non-newtonian fluids (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 92-100 
    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: This paper presents the first theoretical analyses combined with an experimental study of the variables controlling heat transfer rates to non-Newtonian fluids in the streamline-flow region. The theoretical analyses, for the limiting types of non-Newtonian materials, were related to the intermediate case of Newtonian behavior to form a coherent theory applicable to Newtonian and non-Newtonian fluids alike.The experimental data covered Graetz numbers between 100 and 2,000 and were correlated with a mean deviation of 13.5%. The flow-behavior indexes of the three non-Newtonian fluids used varied form 0.18 to 0.70.Some preliminary non-Newtonian results are presented on the problems of nonisothermal fluid-flow pressure losses and heat transfer outside the laminar-flow region. Further theoretical work is recommended in both these areas. Additional experimental data would be of value in all of the problems discussed.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030116
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  • 6
    Electronic Resource
    Electronic Resource
    Flow of non-newtonian fluids - correlation of the laminar, transition, and turbulent-flow regions (1955)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 1 (1955), S. 434-440 
    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: All available data on flow of non-Newtonians in pipes have been correlated on the conventional friction factor  -  Reynolds number plot for Newtonian fluids. This correlation, theoretically rigorous in the laminar flow region, was tested with data on 16 different non-Newtonian materials covering the 2.1 × 109 range of Reynolds numbers from 6.3 × 10-5 to 1.3 × 105. Pipe diameters varied from 1/8 to 12 in. As the correlation does not depend on the type of fluid encountered, it may be used with Newtonian and non-Newtonian fluids alike.In spite of the great range of the available experimetnal data, further work is necessary in the transition and turbulent-flow regions. No data at all were available on thixotropic, rheopectic, and dilatant fluids, and extension of the correlation to these materials should prove most illuminative from both theoretical and practical viewpoints.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690010409
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  • 7
    Electronic Resource
    Electronic Resource
    Diffusion in slurries and in non-Newtonian fluids (1962)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 8 (1962), S. 346-350 
    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: Diffusivities in slurries and in non-Newtonian solutions are predicted by means of an extension of the general Eyring rate theory. The fluid is considered as consisting of a number of discrete regions, each with its own contribution to the overall diffusion process. This model overcomes the unrealistic effects of fluid viscosity predicted by the conventional (empirical) equations. Whereas diffusivities predicted by means of prior art correlations were as much as 230 times lower than the experimental values in the systems, the maximum error in diffusivities predicted with the equations developed in this work was about 40%.Experimental data are provided on two kinds of fluids: slurries and a polymer solution. Both were highly non-Newtonian (flow behavior indexes as low at 0.15). Benzoic acid and β napthol were employed as the diffusing solutes. The principal limitation of the experimental data is that only aqueous systems were investigated.Much further experimental work will be required to provide a truly adequate test of the theory and to evaluate the several unknown parameters in sufficient detail to enable highly accurate predictions. Additionally the model used suggests a possible mechanism for increasing diffusion rates in these systems which is worthy of exploration. It may also be applied to an analysis and prediction of diffusion rates in viscous Newtonian fluids, for which no adequate method is presently available.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690080316
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  • 8
    Electronic Resource
    Electronic Resource
    Agitation of non-Newtonian fluids (1963)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 9 (1963), S. 555-555 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690090427
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  • 9
    Electronic Resource
    Electronic Resource
    Behavior of suspended matter in rapidly accelerating viscoelastic fluids: The Uebler effect (1967)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 13 (1967), S. 316-318 
    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: The observation that large bubbles entrained in accelerating viscoelastic fluids may suddenly stop and remain stationary for long periods of time, although imbedded in a region of high fluid velocities, is noted and described. An analysis of this phenomenon, termed the Uebler effect, shows that it may be expected to occur with all particulate matter provided that the continuum field fluid is accelerating sufficiently rapidly to generate high stresses as a result of fluid stretching, and provided these stresses change sufficiently rapidly in the direction of the velocity vector in the flow field.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690130222
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  • 10
    Electronic Resource
    Electronic Resource
    Turbulence phenomena in drag reducing systems (1969)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 15 (1969), S. 426-434 
    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: An analysis based on the Townsend-Bakewell model of the eddies in the wall regions of turbulent shear flows shows that viscoelastic fluid properties must lead to significant reductions in the rate of production of turbulent energy. This analysis in turn leads to the proper form of the similarity laws for drag reducing fluids, heretofore deduced empirically.Measurements of the axial and radial turbulence intensities for flow through smooth round tubes are reported, as are measurements of the time-averaged velocity profiles and the drag coefficients. These indicate that for solutions exhibiting drag reduction at all Reynolds numbers the flow may be transitional to Reynolds numbers of the order of 105. This transitional flow consists of alternating patches of laminar and turbulent fluid, within each of which the flow characteristics are approximately similar to those of Newtonian fluids. At high Reynolds number conditions with the turbulent field fully developed the velocity profile in the core is flatter under drag-reducing conditions than for turbulent Newtonian fluids, a change dependent on the increased isotropy of the turbulent field of the drag-reducing fluid. These effects appear to be a result of increases in the time scales of the radial fluctuations caused by the fluid properties.Design calculations based upon the present results suggest that in large diameter pipelines, or in boundary layers on large objects, drag reduction may not be attainable under conditions of practical interest until fluids having relaxation times an order of magnitude larger than those presently available, but with comparable viscosity levels, are developed or, alternately, until fluids exhibiting Weissenberg numbers which do not change with deformation rate, can be found.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690150324
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