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  • Chemical Engineering  (45)
  • Lunar and Planetary Science and Exploration
  • Wiley-Blackwell  (45)
  • 1985-1989  (45)
  • 1
    Electronic Resource
    Electronic Resource
    Comments and recommendations on the use of the Avrami equation for physico-chemical kinetics (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1042-1045 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Over the last four decades, numerous reports have appeared on the physico-chemical kinetics, especially crystallization kinetics, based on the Avrami equation, φ = exp [-Ktn] where φ is the fraction of material unchanged at time t, K is an overall rate constant and “n” is the Avrami exponent indicative of process mechanism. The usage of the Avrami equation has been limited to the determination of “n” and its temperature dependence. It is shown that the evaluation of K and the activation energy (E) using this equation is erroneous since K and E are both influenced by “n” although such would be unexpected from the Avrami equation. On the other hand, if one uses a modified expression, φ = exp[-Kt]n, then in addition to the value of “n”, correct values of K and E are obtained. This retains the original correspondence of the Avrami equation to nuclea-tion and crystal growth processes but extends its applicability to (i) correctly evaluate K and E parameters, and (ii) correctly compare transformation rates when the systems differ in their n values. Experimental data are presented to support these conclusions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760281605
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  • 2
    Electronic Resource
    Electronic Resource
    Gas transport in multilayer packaging structures (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 639-644 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Calculation of gas permeation in food packaging structures can be done using a steady-state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time-dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran-coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760291005
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  • 3
    Electronic Resource
    Electronic Resource
    Wave height estimation in stratified gas-liquid flows (1989)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1346-1350 
    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: Andritsos and Hanratty (1978b) have shown that the increase in interfacial drag caused by waves in stratified gas-liquid flows is related to the wave steepness. Recent analyses of finite amplitude Kelvin-Helmholtz waves are used to develop a correlation for the ratio of the wave height to wavelength.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690350813
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  • 4
    Electronic Resource
    Electronic Resource
    Turbulence-producing eddies in the viscous wall region (1989)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1962-1974 
    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 computer simulation of turbulent flow in a channel is used to detect flow patterns related to the production of Reynolds stress. It is found that quadrant 2 and quadrant 4 events possess a streaky structure in the viscous wall region and that these events can be best understood by examining the velocity field in the y-z plane. Large turbulence production in the viscous wall region is found to occur in updrafts and downdrafts associated with closed eddies. These eddies, on average, have a spanwise dimension of 50 wall units and a streamwise dimension of 400-450 wall units. They are often seen to originate from small attached eddies at the wall.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690351207
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  • 5
    Electronic Resource
    Electronic Resource
    Interfacial drag and film height for vertical annular flow (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 895-902 
    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: New measurements are presented for film height and pressure drop for vertical gas-liquid annular flows. Improved methods for predicting the film height and interfacial friction factor are developed for situations in which the liquid film flow rate is known.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310604
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  • 6
    Electronic Resource
    Electronic Resource
    Design of multivariable linear-quadratic controllers using transfer functions (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1481-1495 
    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: Optimal linear-quadratic (LQ) controller design is usually associated with state space techniques. However, when one has measurements of the outputs to be controlled, there are many advantages to designing these LQ controllers using input-output transfer function models. The design procedure leads to a discrete equivalent of the Wiener-Hopf equation, which can be solved using a spectral factorization approach.In this paper the design procedure is presented and various interpretations of the resulting controllers are discussed. In particular, the controllers are shown to be of the internal model controller (IMC) form, and the Wiener-Hopf procedure is shown to be a powerful way of selecting approximate model inverses and filters that yield good performance and robustness characteristics. The approach treats the problem of simultaneous disturbance rejection and set-point tracking, and it easily handles nonsquare systems.The design approach, its performance/robustness trade-offs, and the structure of the resulting controllers are demonstrated using models for several processes, including a two-input/one-output sheet forming process, a (3 × 3) multivariable level control problem, and a (2 × 2) multivariable catalytic reactor.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330908
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  • 7
    Electronic Resource
    Electronic Resource
    Tracer dispersion in sintered glass beads with a bidisperse size distribution (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 610-617 
    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 experimental study was made of tracer dispersion in bidisperse sintered glass materials prepared from mixtures of two sizes of beads with mean diameters of 325 and 95 μm. The equivalent dispersion coefficient increases by a factor of 30 when the porosity decreases from 30 to 12%; this variation is similar to that measured in monodisperse samples. The variation of dispersion can be characterized by the ratio R = ℓd/L1 where ℓd is a length scale deduced from the equivalent dispersion coefficient and L1 is obtained from conductivity and permeability measurements. It is shown that the increase of ℓd/L1 correlates with the loss of porosity during the sintering process. Lightly sintered samples with a percentage of small beads around the minimum of porosity display a nearly Gaussian behavior, with a dispersion coefficient close to that obtained in homogeneous equivalent mixtures. This result is in contrast with very large anomalies observed by other authors. These results imply that dispersion in consolidated samples is sensitive to large-scale inhomogeneities of the materials rather than to their detailed structure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340410
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  • 8
    Electronic Resource
    Electronic Resource
    Relation of oil yield to the structure of the thermal wave in the combustion processing of oil shale (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1263-1274 
    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 combustion retorting of oil shale is analyzed. By using coordinate systems moving at the same velocity as reaction zones, a model is obtained for the fully developed thermal wave which would exist after the wave has progressed a sufficient distance into the bed. Of particular interest is the interpretation of oil yield in terms of the structure of the wave and of operating variables.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310805
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  • 9
    Electronic Resource
    Electronic Resource
    Computer simulation of turbulent mass transfer at a mobile interface (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1108-1115 
    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: Numerical solutions to the unaveraged mass balance equation for the case of a flat mobile interface reveal that both high- and low-frequency velocity fluctuations can contribute to mass transfer. This is in contrast to transport to a solid boundary where only low-frequency fluctuations, normal to the wall, are important. The average mass transfer coefficient is found to depend on Schmidt number to the -0.5 power, in agreement with classical theories. It is related to the velocity field in the liquid primarily through the mean-square value of the gradient of normal velocity fluctuations at the interface.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690320707
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  • 10
    Electronic Resource
    Electronic Resource
    Surface phenomena and mass transfer interactions in liquid-liquid systems (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1069-1076 
    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 surface dynamics of pendant aqueous droplets forming at a submerged nozzle in an immiscible organic solvent have been studied using a novel laser-activated photochromic tracer technique. This enabled a small element of surface to be labeled so that its subsequent history could be recorded photographically.Results for aqueous droplets forming in toluene in the absence of any mass transfer indicated only a slow interfacial circulation from the front to the rear, and there was no indication of any surface renewal as a result of hydrodynamic flow even at nozzle Reynolds numbers as high as 300. By contrast, the introduction of any one of a number of organic solutes into the toluene phase led to sporadic Marangoni-type interfacial disturbances, which in turn resulted in rapid replacement of elements of the droplet surface. It is proposed that renewal of the droplet surface is dependent on solute diffusion in the present instance and that the processes of surface renewal and mass transfer are likely to be interactive.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310704
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