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  • 1995-1999  (2,386)
  • 1995  (2,386)
  • General Chemistry  (1,656)
  • Chemical Engineering  (730)
  • 101
    Electronic Resource
    Electronic Resource
    The effect of drawing temperature on multi-stage drawn ultra-high molecular weight polyethylene (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1555-1561 
    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: The effect of drawing temperature on multi-stage drawn ultra-high molecular weight polyethylene (UHMWE) fiber, produced by gel spinning, has been studied. Drawing at higher temperature generally gives higher crystal orientation, as expected. The activation energy of drawing increased with the draw ratio and raw 4sequence. It varied at a given draw ratio and draw stage between two temperature ranges, 85 to 115°C and 115 to 135°C. Thus, for the first draw stage, the activation energy is ∼ 19 - 35 KJ/Moe in the range of 85 to 115°C, and ∼ 60 - 99 KJ/mole in the range of 115 to 135°C. In the second stage, the activation energy is 40 KJ/mole in the range of 105 to 115°C and 70 - 99 KJ/mole in the range of 115 to 135°C. In the third stage, the activation energy is ∼ 92 - 100 KJ/mole in the range of 115 to 135°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351909
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  • 102
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352001
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  • 103
    Electronic Resource
    Electronic Resource
    Polymer research in korea (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1581-1582 
    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: This special issue is dedicated to the current and rapidly growing polymer research in Korea. The isue contains a grouping of typical research studies from Korea. The set is not inclusive, as there are many fine additional research programs under way in Korea. A brief history and comments on several aspects of Korean polymer research may provide a perspective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352002
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  • 104
    Electronic Resource
    Electronic Resource
    A cure study on alumina trihydrate reinforced allylester resins by differential scanning calorimetry (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1583-1591 
    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: Allylester prepolymers were synthesized by transesterification, and curing kinetics of alumina tihydrate reinforced allylester resins was studied by means of a differential scanning calorimetry dynamic experiment. The activation energies and the frequency factors of the reinforced allylester prepolymers were estimated by means of Ozawa's and Kissinger's methods. The values determined from the Ozawa method are higher than those from the Kissinger method. The peak exotherm temperature of reinforced allylester resin was shifted to a lower temperature as the concentration of curing agent increased. The peak exotherm temperature as the concentration of curing agent increased. The peak exotherm temperature of reinforced allylester resin was, however, shifted to a higher temperature as the content of alumina trihydrate increased. In the case of the dynamic experiment, both the activation energy and the frequency factor decreased as the concentration of curing agent was increased. Meanwhile, there exist minimum values of both the activation energy and th frequency factor with varying contents of alumina trihydrate.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352003
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  • 105
    Electronic Resource
    Electronic Resource
    Blends of thermotropic liquid crystalline polyesters and poly(butylene terephthalate): Thermal, mechanical, and morphological properties (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1605-1614 
    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: Blends of poly(butylene terephthalate) (PBT) with three different thermotropic liquid crystalline polyesters (TLCPs) were prepared. The first TLCP (HBH-6) consists of diad aromaticester type mesogenic units and the hexamethylene spacers along the main chain, and the second (TB-S6) is a wholly aromatic polyester TLCP having alkoxy side groups on the terephthaloyl moiety. The last (TR-4,6) is an LC copolymer comsisting of triad aromatic ester type mesogenic units and two differents spacers; tetramethylene and hexamethylene units. Blends of TLCP with PBT were melt spum at different LCP contents and differnt draw ratios to produce monofilaments. For the HBH-6/PBT and TB-S6/PBT blends, the ultimate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increased up to 20%. On the other hand, the initial modulus monotonically increased with increasing LCP content in all cases. The blends with TB-S6 showed the highest tensile properties of the three blends systems. This can be ascribed to the highest rigidity of the polymer chain, which still carries relatively long alkoxy substituents that promote sufficient adhesion between the LCP and PBT matrix. When compared with the PBT fiber itself, the fibers obtained from the 5% TB-S6/PBT blends exhibited an improvement in tensile strength by 〉 25% and in tensile modulus by ∼ 200%.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352006
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  • 106
    Electronic Resource
    Electronic Resource
    Effect of die geometry on the structural development of a thermotropic liquid crystalline polymer in a thermoplastic elastomer matrix (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1621-1628 
    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: This study investigates deformation of a thermotropic liquid crystalline polymer (TLCP) in different die geometries. Blends of aTLCP with a thermiplastic elastomer of EPDM were made in a twin-screw extruder. Morphological observation of the extruded blends demonstrates the complimentary effect of shear in the die exit on dispersed phase deformation and fibril formation. Shear strain can affect fibril formation for a relatively large dispersed phase in the region close to the die wall. However, the main role of shearing is in breaking up the larger particles and initial polydomain structure. A strong elongational deformation on the blended melt after the die exit is required, and fine microfibrils normally obnserved in in situ composites were not easily formed by shear deformation only in the die.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352008
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  • 107
    Electronic Resource
    Electronic Resource
    Rheological study on poly-D(-)(3-hydroxybutyrate) and its blends with poly(ethylene oxide) (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1636-1642 
    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: Aspects of thermal, morphological, and rheological properties of biodegradable poly-D(-)(3-hydeoxybutyrate) (PHB) blended with poly(ethylene oxide) (PEO) have been studied. Thermal properties and morphology of the blends were examined by scanning electron microscopy and differential scanning calorimetry, respectively. A rotational theometer with parallel plate geometry was also adopted to investigate the rheological properties of these blends. In addition, dynamic ciscoelasticity was measured by a Rheovibron as functions of time and temperature. From these measurements, PHB and PEO were observed to be miscible in the melt state. In the case of the blend systen 80/20 PHB/PEO by weight, the vacant domains of the PHB were filled with PEO particles, and this morphological state enhanced the rheological properties. Furthermore, PHB and its blends were found to have high crystallinities, but to have unstable thermal behavior about Tm.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352010
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  • 108
    Electronic Resource
    Electronic Resource
    Morphology and dynamic mechanical properties of nylon 66/ poly(ether imide) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1643-1651 
    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: The morphology and dynamic mechanical properties of blends of poly(ether imide) (PEI) and nylon 66 over the full composition range have been invesigated. Torque changes during mixing were also measured. Lowertorque values than those calculated by the log-additivity rule were ontained, resulting from the slip at the interface due to low interaction between the componeents. The particle size of the dispersed phase and morphology of the blends were examined by scanning electron microscopy. The composition of each phase was calculated. The blends of PEI and nylon 66 showed phase-seoarated structures with small spherical domains of 0.3 ∼ 0.7 μm. The glass transition temperatures (Tgg) of the blends were shifted inward, compared with those of the homopolymers, which implied that the blends were partially imiscible over a range of compositions. Tg1, corresponding to nylon 66-rich phase. This indicated that the fraction of PEI mixed into nylon 66-rich phase increased with decreasing PEI content and that nylon 66 was rerely mixed into the PEI-rich phase. The effect of composition of the secondary relaxations was examined. Both Tβ, corresponding to the motion of amide groups in nylon 66. and Tγ′, corresponding to that of either groups in PEI, were shifted to higher temperature, probably because of the formation of intermolecular interactions between the components.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352011
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  • 109
    Electronic Resource
    Electronic Resource
    Determination of relaxation time spectra by analytical inversion using a linear viscoelastic model with fractional derivatives (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1661-1669 
    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: Recently, Friedrich proposed an empirical model for linear viscoelastic fluids corresponding to a constitutive equation with fractional derivatives [Phil. Mag. Lett., 66, 287 (1992)]. For this model, the relaxation modulus, the dynamic moduli, the relaxation time spectrum, and other material functions have been explicitly calculated as a function of the few parameters that characterize a viscoelastic fluid within this model. By fitting this model to experimental data, the model parameters can be determined and other material functions, in particular the relaxation time spectrum, can be calculated immediately. This paper reports to what extent this method, which may be called analytical inversion, is appropriate for the determination of relaxation time spectra. For that pupose, the spectra of a number of very different polymeric materials are determined with this method. The spectra calculated in this way are compared with the spectra obtained by nonlinear regularization. It turns out that the empirical model describes the linear viscoelastic properties of a variety of different materials with high accuracy. Keeping in mind that the determination of the relaxation time spectrum requires the solution of an ill-posed problem, the agreement between the relaxation time spectra obtained by analytical inversion and by regularization is satisfactory for these materials.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352102
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  • 110
    Electronic Resource
    Electronic Resource
    Steady-State and dynamic properties of concentrated fiber-filled thermoplastics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1670-1681 
    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: Rheometric data for short-fiber-filled thermoplastics are presented using a parallel-plate viscometer. Polypropylene tensile bars contain short and long fibers with glass weight percentages of 0%, 5%, 10%, 20%, and 30%, polycarbonate tensile bars with glass percentages of 0%, 5%, and 10% long fibers, and nylon 6/6 tensile bars with 0%, 15%, 30%, and 45% short fibers. The short fibers were initially 3 mm in length and 12.7 microns in diameter. The long fibers were initially 6 mm in length and 10 microns in diameter. In the steady-state experiments, the fibers increase the viscous stresses and the normal stresses in proportion to the concentration of fibers. At low shear rates, the viscosity is increased by the addition of the fibers, but at high shear rates the viscosity approaches that of the neat resin. In dynamic testing, the fibers increase the viscous and elastic components as measured by the complex viscosity and modulus. The fibers increase the viscous and elastic nature of the fiber-filled composite at low frequencies and to a lesser extent at higher frequencies. The fibers increase the elastic component more than the viscous component at low frequencies and less at higher frequencies as demonstrated by tan δ.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352103
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  • 111
    Electronic Resource
    Electronic Resource
    Stress-Strain curves for solid polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1725-1732 
    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: In order to provide nw experimetnal facts required for constructing a nonlinear constitutive equationfor solid polymers, some tests wee conducted on amorphous pojymers of polycarbonate and poly(methyl methacrylate) and for a crystalline polymer of polyxymethylene under varous strain paths such as comprssion, torsion and combined tension-torsion. It is shown that (1) the stress-strain behavior for the strain paths without strain reversal is described well not only for amorphous polymers, but also for crystalline polymers by an overstess theory proposed by Krempl, and (2) at the strain paths wth stran reversal, the stress responses are considerably differetn from what is expected for the fstress responses of metals and their alloys.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352202
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  • 112
    Electronic Resource
    Electronic Resource
    The hybrid FEM/FDM computer model for analysis of themeteirng section of a single-screw extruder (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1748-1757 
    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: A hybrid FEM/FEM computer model was employed n this studyfor simulating the non-newtonian, nonisothermal polymr melt fielt in the inetering section of a single-screw extruder. The pressure distribution in the screw surface was obtained by solving the generalized Reynolds equation. Instead of using the energy equation in Eulerian frame, a Lagrangian expression ws involved for stabilizing the numerical scheme. The temperature profiles wee obtained by finite difference discretizaton for the energy equation in such element. The screw surface with the screw channels and the flight lands could be modeled as a surface divided into small shell elements. To demonstrate aplicability, the results provided by the hybrid FEM/FDM were found to be similar to those of the 2D FDM for the trhermally developing flow, through Fenner's example. It can also ilustrate the leakage flow and the cross-channel effect in the screw pumping problem. The results from the Hybrid FEM/FDM revealed that if the clearance becomes too large, the volumetric flow rate would considerably decrease and the exist melt temperature would increase. In addtion, when the clearance is close to the normal design clearance, the leakage flow through the flight lands was found to be small. These computational results were observed to correlate with those of other experimental studies. Finally, the hybrid FEM/FDM approach can in principle be extended to the non-Newtonian, nonisothermal flow in a complex screw surface such as the barrier screw and the Maddock mixing head.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352204
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  • 113
    Electronic Resource
    Electronic Resource
    Low shear viscosity and crystallization in dilute solutions of polymers at high pressures: Falling body viscometry of high molecular weight polyethylene solutions (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1781-1784 
    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: A specially designed falling body viscometer has been used to obtain low shear viscosities of dilute solutions of high molecular weight polyethylene in decalin and for detecting phase transitions at high pressures. The method provides valuable rheological data at pressures that correspond to those I lubrication and some extrusion processes. In addition, the method enables detection of phase transitions, such as crystallization, that result in detectable changes in rheology. The influence of pressure as high as 0.6 GPa ( ∼ 80.000 psi) is illustrated here through a study of crystallization, with verification from light scattering and calorimetry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352207
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  • 114
    Electronic Resource
    Electronic Resource
    Compatibility of poly(ethylene 2,6-naphthalate) and poly(butylene 2,6-naphthalate) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1807-1810 
    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: Blends prepared from poly(ethylene 2,6-naphthalate) (PEN) and poly(butylene 2,6-naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed: brittle for the blends 〈 20 wt% of PBN, while ductile 〉 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352210
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  • 115
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352301
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  • 116
    Electronic Resource
    Electronic Resource
    Effects of mixing porcedures on properties of compatibilized polypropylene/nylon 6 blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1821-1833 
    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: The paper consides the effects of compatibilization with maleic anhydride grafted polypropylene (PP-g-MAH) on the propertie of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes; single-step blending, two-step blending with reactive premixing, and two-step blending with nonreactive premixing, to determine the effective mixiing process for fine morphological structure thermal stability, and mechanical properties. Dynamic melt reheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addtion, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilizaton. The results show that compatibilized blends prepared by teh single-step process exhibit improved phase morphology, thermal stability, and mechanical properties for dried conditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two-step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moisture absorption.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352302
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  • 117
    Electronic Resource
    Electronic Resource
    A hybrid numerical technique to model 3-D flow fields in resin transfer molding processes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1834-1851 
    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: A hybrid two-/three-dimensional solution technique is presentedto model 3-D flow fields in resin transfer moeling using Darcy's low. The 3-D flow field is only solved for regions where all three velocity components are significant, thus largely reducing the number of unknowns. Elsewhere, the commonly used 2-D approximation for flow in thin gaps between plates is employe.d The method is applied to regions where the flow splits, such as T-joints. Because of the uncertainties associated with an accurate determination of the permeability in these regions, a simplified decompled procedure is procesed, which reduces the computational complexity. In this procedure, the flow front is advanced using the 2-D formulation. The 2-D formulation also provides the boundary conditions for the subsequent computation of the 3-D flow field without feedback of flow field information to the 2-d model. The governing equations are solved using boundary fitted coordinate systems (BFCS) together with the finite difference method (FDM). Numerical as well as algebraic grid generation and domain decomposition are employe dto generate grids that always concide with the continuously deforming and enlarging flow domain. Results that include the trackingof numerical tracer particles to visualize the three-dimensionality of the flow field are presented for isothermal flow of a Newtonian fluid through a T-joint. This detailed flow field description is expected to form the basis for a rather accurate simulation of quantitities that largely depend on the fluid particle pathlines, such as the degree of cure. The method is also extendable to shear-thinning fluids as well as to 3-D flow in the vicinity of the flow front.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352303
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  • 118
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    Electronic Resource
    Theory of competition between breakup and coalescence of droplets in flowing polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1872-1877 
    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: The Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352306
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  • 119
    Electronic Resource
    Electronic Resource
    Performance of reprocessed multilayer LDPE/nylon-6 film (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1878-1883 
    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: Multilayer LDPE/nylon-6 films with an overall content of 71 wt% LDPE, 24 wt% nylon-6, and 5 wt% PE-based tie-layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy-to-break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low-density polyethylene) and nylon-6 was retained, whereas in extensively mixed samples, nylon-6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O2 and H2O vapor barrier properties, whereas extensively-mixed samples had poor barrier properties. Properties of well-mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon-6 components.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352307
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    Assessment of residual stresses during cure and cooling of epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1895-1898 
    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: A new stress monitoring technique, a stress-tracking device, is described here. It has been used to study some important properties of epoxy resin. Residual stresses, including a curing shrinkage stress and a cooling shrinkage stress, were measured automatically and continuously during curing and cooling. Simultaneously, information such as an apparent gelation time and glass transition temperature were obtained directly during the experiment. These epoxy resin properties were related to the extent of cure. Varying cure temperature produced changes of cure behavior, which resulted in different residual stresses.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352309
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  • 121
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    Study of reaction injection molding of polyurethane microcellular foam (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1899-1906 
    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: Processing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas-supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether-based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas-supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure 〈 2.0 MPa.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352310
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  • 122
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    Modeling the mechanical properties in polypropylene/polyamide-6 blends with core shell morphology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1917-1922 
    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: Polypropylene/Polyamide-6 (PP.PA) blends containing maleic anhydride grafted elastomers were prepared by reactive blending. Three different types of core shell morphologies were obtained and characterized by transmission electron microscopy (TEM). The midulus of these elastomer midified PP/PA (70/30) blends with core shell type morphology is compared to predictions derived from the Kerner model. The multiphase morphology of these blends could be modeled by sequential application of the Kerner equation to two-phase subinclusions. Using morphological data ontained by TEM, good agreement between experimental and calculated values was ontained. The results are used to tailor PP/Pa-6 blends combining stiffness and toughness.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352402
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    Creep analysis of thermiplastics using stress relaxation data (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1931-1937 
    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: One of the major factors limiting the use of thermoplastics in engineeing applications is the inadequacy of existing design data. Much of the data do not span appropriate ranges of stress, strain, time, or temperature. This study addresses the need to develop an accelerated method for generating long-time design data to support the innovative use of engineering thermoplastics. In particular, stress relaxation tests (SRT) were performed on polycarbonate (PC) and midified poly(phenylene oxide)(PPO), and used to generate time-dependent design data through the short-time measurement of the material's current state without dependence on elastic modulus. The test results and analyses reported here indicate the SRT method to be an efficeint means of generating accurate and repeatable creep and secant modulus data which may be directly used in design. Therefore, SRT shows great potential both as a design parameter development tool, and as a quality control instrumetn for assessing batch-to-batch variability.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352404
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  • 124
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    Processing and morphology of polystyrene/ethylene-propylene rubber reactive and nonreactive blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1938-1948 
    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: The difference between reactive and nonreactive polymer blends in terms of processing and morphology has been investigated. The glassy phases for the blends are an oxazoline functional polystyrene (PS-Ox) and a similar non-functional polystyrene (PS). The rubbery phases are an ethylene-propylene rubber (EP) and a similar ethylene-propylene rubber (EP-MA) with 07% grafted maleic anhydride. In the case of PS-Ox/EP-MA blends, the oxazoline group may react with the grafted rubber functionality at the interface between the two immiscible components during blending to form a compatibilizing agent in-situ. The nonreactive blends systems of PS-Ox/EP and PS/EP-MA were used for comparison to the reactive system. The blend components are rheologically matched to simplify the interpretation of the process and morphological data. The blends were prepared in a batch mixer with roller blades. The torque required for mixing was measured during the blending process. The torque traces for the reactive blends exhibited a peak in torque, attributed to the chemical reaction at the interface. The weight fraction of gel in the blends was used to measure the extent of reaction. It correlates well with the mixing torques and rheological properties. The nonreactive PS-Ox/EP and PS/EP-MA blends show poor interfacial adhesion between the two phases. In contrast, the reactive PS-Ox/EP-MA blends show excellent during annealing is also much greater for the reactive blends. Varying the functionality concentration in the PS phase shows that the dispersed phase rubber particle size is reduced by increasing the concentration of oxazoline in the matrix. Blends with no or small amounts of functionality in the PS phase exhibit yield behavior in tension. However, a level of concentration of reactive functionality may be reached where the material becomes brittle.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352405
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    Impact testing of polypropylene blends and comosites (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1962-1971 
    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: Polypropylene (PP) composites containing 0.30 vol% of talc filler, in addtion to blends modified with an ethylene-propylene copolymer (EPR) elastomer were prepared and their fracture resistance was determined by the standard Ixod impact test and by a fracture mechanics technique. Effects of composition, type of modification, specimen size, and temperature were studied. The validity of linear elastic freacture mechanics (LEFM) conditions were checked: It was shown that under the conditions applied they can be satisfied even twith specimens of reasonable size (4 × 10 × 80 mm) prepared by conventional processing techniques. Calculations of minimum specimen thickness must be carried out, with material properties obtained under the conditions of impact. For heterogeneous blends and composites yield stress should be corrected for the effect of decreasing load-bearing cross section. Linearity of the fracture energy (U) vs. BDφ or U vs. B(D - a) plots is not a proof for either elastic of plastic fracture. The composition dependence of fracture properties proved to be practicaly independent of specimen size, temperature, or measurement technique.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352408
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  • 126
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    Thin-film thermoplastic-metal joining process for titanium to poly(etherketoneetherketoneketone) (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1972-1978 
    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: The processing of high temperture thermoplastic polymers as a hot melt adhesive is one means of joining thermoplastics to metals. The presetn study establishes the role of processing in thermoplastic joining of a titanium alloy (Ti-6A1-4V) using thin flim poly(etherketoneetherketoneketone) (PEKEKK). A design of expriments (DOE) was performed to determine the effects of the soak above melt temperature (Tm = 380°C), hold at the isothermal recrystallizztion temeprature (Tiso = ∼ 340°C) and cooling rates on the joint strength, Extended soak times are required to remove the residual spherulitic crystallinity in the polymeric adhesive. Whit the elimination of the residual crystallinity, high-strength transcrystalline regions are enhanced at the polymer-metal interface during the hold time at Tiso and during cooling to ambient temperature. Average tensile strengths of 137 MPa were achieved, exceeding the bulk polymer tensile strength of 118 MPa by 16%, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) show that extended soak times above Tm led to excessive polymer squeeze-out, resulting int he creation of strength-reducing shrink voids or unwetted regions. As a result, the failue mode of the joint, which was normally cohesive for high-strength joints, became a mix of cohesive and adhesive in parts with excessive polymer squeeze out.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352409
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  • 127
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    Direct-contact steam condensation with simultaneous noncondensable gas absorption (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 241-250 
    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: Experimental results are reported on simulataneous heat transfer and gas dissolution during the direct-contact condensation of steam on water in the presence of CO2. A column filled with structured packing is used as condenser with the water in counterflow with the steam/CO2 mixture. The region along the column where the bulk of condensation takes place is controllable by suitable choice of the steam/water ratio. Measured local heat-transfer coefficients change by roughly an order of magnitude from the bottom to the top of the column. The extent of CO2 dissolution in the water/condensate under most conditions is unexpectedly high and depends strongly on the exit liquid temperature. A driving force based on the interfacial CO2 concentration, not the overall concentration difference used in conventional absorption operations, is suggested as more appropriate to describe the phenomenon. The data are complemented with preliminary results from a computational model based on the integration along the column of local heat- and mass-transfer rates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410206
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  • 128
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    Flow regimes of the three-phase circulating fluidized bed (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 267-271 
    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: Gas-solids circulating fluidized beds have been successfully used in catalytic cracking of heavy oil, coal combustion, and some metallurgical and physical processes (Grace, 1990). Gas-liquid-solids fluidized beds are operated mainly in conventional fluidization regimes without solids circulation or in the transport regime with low solids holdups (less than 5%) (Fan, 1989). A circulating/fast fluidization regime, however, has not been studied. A three-phase circulating fluidized bed has several potential applications in biochemical and chemical processes. Three-phase fluidized-bed bioreactors generally use light and small particles (Berk et al., 1984). Circulating operation can promote solids mixing and increase product throughput per unit bed cross section, while high shear stress can promote biofilm renewal (Pirozzi et al., 1990). In three-phase hydrotreating reactors, solids catalysts lose their activity due to the deposit of metal and coke on the surface. Circulating operation not only regenerates deactivated catalyst continuously using accompanying downcomers but also transfers heat to and from the reactor. This article discusses the flow regimes of the three-phase circulating fluidized bed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410209
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    Liquid holdup in rotating packed beds: Examination of the film flow assumption (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 301-316 
    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: Possibilities of predicting liquid holdup in rotating packed beds are examined using the film flow theory. A hydrodynamic model based on film flow on the particle scale accommodates both laminar and turbulent films in the entry and developed regime. Conductance measurement was used for experimental determination of liquid holdup and estimation of the degree of anisotropy of liquid distribution. Experimental results represent the first data for liquid holdup in the rotating packed bed as a function of operating conditions and liquid properties. They indicate an anisotropic liquid distribution dependent on the operating variables. While the film model can be fitted to the experimental data, such a fit lacks a theoretical basis and the classical theory of film flow on the particle scale cannot explain the liquid flow in rotating packed beds. An empirical expression correlates well the holdup data with the operating parameters.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410212
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  • 130
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    Nucleation and growth in microcellular materials: Supercritical CO2 as foaming agent (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 357-367 
    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: Bubble growth is a phenomenon encountered in several commercially important processes. A mathematical model presented here describes the growth of bubbles during phase separation of an initially homogeneous polymer-supercritical fluid mixture, triggered by a sudden pressure drop at constant temperature. It is a modification of the viscoelastic model of Arefmanesh and Advani (1991) in which the polymer is treated as a single relaxation-time Maxwell fluid. Since properties of the polymer-fluid mixture vary with the amount of fluid absorbed in the polymer (as a function of fluid pressure), the model needs to be used evaluating system properties as functions of temperature and pressure. The viscosity of polymer/fluid mixture, density of the mixture, diffusivity of CO2 in the mixture, and relaxation time for poly (methyl methacrylate) swollen by supercritical carbon dioxide are, therefore, predicted as functions of CO2 pressure and temperature using appropriate model equations at each step of the bubble growth simulation. The model predicts well the trends in equilibrium cell size vs. saturation pressure and temperature.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410217
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  • 131
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    Protein transport in ultrafiltration hollow-fiber bioreactors (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 415-425 
    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 1-D model, which neglects radial variations, describes the hydrodynamics of cell-free ultrafiltration hollow-fiber bioreactors (HFBRs) and the transport of highmolecular-weight proteins trapped in the extracapillary space (ECS). The profiles of radially-averaged protein concentrations predicted by this model are identical to those obtained using a model with radial variations. The model predictions agree well with axial profiles of bovine serum albumin (BSA) and human transferrin concentrations measured in transient and steady-state experiments. The validated model explores the influence of cell culture operating conditions on HFBR protein transport. Increasing protein loading decreases BSA and transferrin polarization in HFBRs operated with unidirectional lumen flow. A relationship developed predicts the protein loading needed to ensure a nonzero steady-state protein concentration throughout the ECS. This critical protein loading depends only on the lumen pressure drop and the ECS protein osmotic pressure. Periodic reversal of the lumen flow direction also decreases protein polarization. The influence of the flow-direction switching time and membrane permeability on the ECS protein distribution is investigated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410222
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    3-D mapping of solids flow fields in multiphase reactors with RPT (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 439-443 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410226
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690410301
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  • 134
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    AIChE journal: More diverse and timely (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 445-445 
    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.690410302
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  • 135
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    Mass and heat transfer in crushed oil shale (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 446-455 
    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: Studies of heat and mass transfer in packed beds, which disagree substantially in their findings, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse irregular shapes and sizes. We, in 349 runs, measured mass-transfer rates from naphthalene particles buried in packed beds by passing through air at room temperature. An exact analogy between convection of heat and mass makes it possible to infer heat-transfer coefficients from measured mass-trans-fer coefficients and fluid properties. Some beds consisted of spheres, naphthalene and inert, of the same, contrasting or distributed sizes. In some runs, naphthalene spheres were buried in beds of crushed shale, some in narrow screen ranges and others with a wide size range. In others, naphthalene lozenges of different shapes were buried in beds of crushed shale in various bed axis orientations. This technique permits calculation of the mass-transfer coefficient for each active particle in the bed rather than, as in most past studies, for the bed as a whole.The data are analyzed by the traditional correlation of Colburn jD vs. Reynolds number and by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: local Reynolds number should be based on the active-particle size, not the average for the whole bed; differences between shallow and deep beds are not appreciable; mass transfer is 26% faster for spheres and lozenges buried in shale than in all-sphere beds; orientation of lozenges in shale beds has little or no effect on mass-transfer rate; and for mass or heat transfer in shale beds, log(j·∊) = - 0.0747 - 0.6344logNRe + 0.0592log2 NRe.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410303
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    The effect of gravity degradation on low-speed centrifuge capillary pressure data (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 469-480 
    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 gravity degradation effect has been identified as a significant physical problem in using centrifuge techniques for determining capillary pressure curves. In 1992, the authors characterized the effect by an angle; however, such an evaluation is simplistic. Here, a new model is constructed to characterize the effect quantitatively. The results with simulated data sets show that there exists a pronounced effect of gravitation on the horizontal centrifugal field in low-speed experiments (≤ 500 rpm on a standard Beckman centrifuge). Gravity affects the production history for some samples, which leads to inaccurate interpretations of capillary pressure information near the threshold pressure.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410305
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  • 137
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    New sorbents for olefin/paraffin separations by adsorption via π -complexation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 509-517 
    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 adsorbents for olefin/paraffin separation are synthesized by effective dispersion of Ag(I) and Cu(I) cations on substrates with hydrocarbon-phobic surfaces. These cations bind olefin molecules by a π-complexation bond, a weak chemical bond. Ethane/ethylene and propane/propylene separations are considered. Cation exchange resins and CuCl/γ-Al2O3 are effective substrates. On the Ag(I) resin at 25°C and 1 atm, the equilibrium adsorption ratio for C2H4/C2H6 = 9.2 and C2H4 capacity = 1.15 mmol/g; the corresponding values for C3H6/C3H8 = 10.4 and C3H6 capacity = 1.29 mmol/g. The CuCl/γ-Al2O3 sorbent shows equally promising results. The sorption rates are pore-diffusion-controlled and rapid. The olefin selectivity; capacity, and rates are much higher than all previous attempts and are suitable for applications in cyclic adsorption processes.The equilibrium data are correlated with an isotherm equation that accounts for both physical adsorption and π-complexation with energy heterogeneity, using only two true fitting parameters. Molecular orbital calculations using a C6H5SO3- substrate indicate that the π-complexation bond is contributed mainly by the donation of olefin π-bond electrons to the empty s-orbital of the metal, while the d-π* back donation contributes only 16%. Moreover, the relative order of the heats of adsorption is correctly predicted.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410309
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    Agglomeration during precipitation: II. Mechanism deduction from tracer data (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 525-535 
    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 novel approach using a 2-D population balance model is developed and applied to the analysis of experimental tracer crystal data. This approach is effective in discriminating among various functional forms of agglomeration kernel and enables estimation of the agglomeration kinetics. At present, the analysis is restricted to three simple agglomeration kernels and shows that the size-independent kernel best describes the agglomeration of Al(OH)3 crystals during precipitation in caustic aluminate solutions. This agrees with the findings of Ilievski and White (1994). Estimates of the agglomeration kinetic parameters from the tracer data agree well with the experimentally observed values.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410311
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  • 139
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    Solvent effect on adsorption phenomena in reversed-phase liquid chromatography (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 536-547 
    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 effect of solvent and mobile-phase composition on adsorption characteristics in liquid-phase absorption is studied. Comparing experimental adsorption data for several organics in both gas- and liquid-phase systems confirms that adsorption equilibrium constant K and isosteric heat of adsorption Qst are smaller than those in corresponding gaseous systems. The logarithm of K almost linearly increases as methanol composition decreases. Solvophobic theory applied quantitatively analyzes these solvent effects. Estimation methods for three parameters influence calculation results: solvent effects on K can be quantitatively analyzed; the adsorbability of adsorbates can be estimated from the value of ΔGsolv for each homologue in a reversed-phase liquid chromatographic system; and the solvent effect on Qst cannot be satisfactorily interpreted. It is, however, confirmed that Qst is influenced by a solvent and an apparent small value is observed in liquid-phase adsorption.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410312
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    Chromatographic study on liquid-phase adsorption on octadecylsilyl-Silica Gel (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 548-558 
    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: Adsorption characteristics of reversed-phase liquid chromatography and influence of solvent composition on the characteristics are studied by the chromatographic method and the moment analysis. Adsorption equilibrium constant increases by adding hydrophobic increments into adsorbate molecules. Contributions of fluid-to-particle mass transfer and intraparticle diffusion to mass-transfer resistance in the octadecylsilyl-silica gel (ODS) column are almost equally great. Surface diffusion is dominant for the intraparticle diffusion in ODS. The logarithm of the surface diffusion coefficient linearly increases with an increases with an increase in methanol fraction in the range from 40 to 100 vol. %. In liquid-phase adsorption, activation energy of surface diffusion is greater than the isosteric heat of adsorption and both increase when methanol fraction decreases in the range from 40 to 100 vol. %. An empirical correlation based on experimental data proposed estimates surface diffusion coefficients from physical properties of adsorbates.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410313
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  • 141
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    Sol-gel preparation and properties of Alumina adsorbents for gas separation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 559-570 
    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 sol-gel method is applied to prepare Cu+ or Ag+ containing alumina adsorbents which have potential application in purification or separation of carbon monoxide or olefins containing gases. Wet impregnation and sol-solution mixing methods are used to incorporate the active species into the sol-gel derived γ-alumina support. These alumina adsorbents have the characteristics of large specific surface area, high dispersion of active specie on the grain surface, and mesopore size with a uniform pore size distribution. The gas chromatographic technique determines the carbon monoxide adsorption properties on these alumina adsorbents. Adsorption equilibrium constants, adsorption rate constants, axial dispersion coefficients, heat of adsorption, and adsorption activation energy are determined from GC response peaks by using the moment method. The alumina adsorbents prepared by the solgel method appear to be superior to the similar adsorbents prepared by other methods.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410314
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  • 142
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    Adjustable discretized population balance for growth and aggregation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 591-603 
    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 discretized population balance (DPB) of Hounslow et al. (1988) is extended to allow the use of an adjustable discretization of the size domain of the form νi+/ν1=2 1/q (where q ≥ 1 and is an integer). All the advantages of Hounslow et al.'s original work are retained: the zeroth and third moments of the particle-size distribution are correctly predicted, and the DPB is simple to solve with no integration within each size interval. The predicted and analytical particle size distributions are in excellent agreement for the cases of nucleation and growth and aggregation alone in batch and in continuous vessels. High-order moments and self-preserving particle-size distributions are accurately predicted when q ≥ 4.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410317
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  • 143
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    Glucose hydrolysis and oxidation in supercritical water (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 637-648 
    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: Glucose hydrolysis and oxidation occurred rapidly in supercritical water at 246 bar and at 425 to 600°C. A diverse set of products, present in the liquid-phase reactor effluent and also subject to hydrolysis, was formed. At 600°C and a 6-s reactor residence time, glucose is completely gasified, even in the absence of oxygen. In the presence of oxygen, destruction of liquid-phase products is enhanced, with none found above 550°C at a 6-s reactor residence time. Major products formed wee acetic acid, acetonylacetone, propenoic acid, and acetaldehyde in the liquid phase, and carbon monoxide, carbon dioxide, methane, ethane, ethylene, and hydrogen in the gas phase. Methane and hydrogen were present among the products at temperatures up to 600°C for reactor residence times of 6 s.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410320
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  • 144
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    Simplified local density model for adsorption over large pressure ranges (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 838-845 
    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 mean-field model is developed that superimposes the fluid-solid potential on a fluid equation of state to predict adsorption on a flat wall from vapor, liquid, and supercritical phases. A van der Waals-type equation of state is used to represent the fluid phase, and is simplified with a local density approximation for calculating the configurational energy of the inhomogeneous fluid. The simplified local density approximation makes the model tractable for routine calculations over wide pressure ranges. The model is capable of prediction of Type II and III subcritical isotherms for adsorption on a flat wall, and shows the characteristic cusplike behavior and crossovers seen experimentally near the fluid critical point.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410411
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  • 145
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    A product distribution paradox on scaling up a stirred batch reactor (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 855-867 
    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: For a triplet competitive-consecutive halogenation sequence forming mono-, di- and trihalogenated products of the form, A + B → R + B → S + B → T, under semibatch operation adding B to A, if perfect mixing could be assumed at all scales, the product distribution would be unchanged on scaling up. However, if the reaction rates are reasonably faster than the mixing rate, the semibatch addition of B to A will be imperfectly backmixed, exhibiting macroscale concentration gradients. This partial segregation of the primary reagents is capable of modifying the selectivity and corresponding appearance of R, S and T in the course of the batch. Imperfect mixing is quantified using the networks-of-zones model. The effect of scaling up at equal tip speed is examined for a lab-scale 0.3-dm3 reactor, a semitech 30-dm3 reactor, and a production-scale 3,000-dm3 vessel. The intensity of partial segregation is weak at the lab scale, but very severe at the production scale. The lab-scale reactor is therefore close to perfectly backmixed, and the primary, secondary and tertiary products appear in sequence. At the semitech scale the increased partial segregation causes the final product to initially precede the secondary product paradoxically but lag the initial product. At the large scale the more severe segregation between A and B gives an even greater paradox, whereby the final product appears ahead of both the primary and secondary ones. The segregated concentration fields of A and B are visualized as sectional image reconstructions for networks comprising on the order of 1,000 zones. Localized intensive plumes of B emanating from the addition point cause the paradoxical reversals of product sequences. The calculations are directly relevant to real industrial miscible liquid halogenations for which product distribution paradoxes have been observed (Haywood, 1990).
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410413
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    Characterization of structural inhomogeneities in porous media (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 894-906 
    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: Recent studies have demonstrated that spatial heterogeneities in voidage and pore size, over lengthscales of 0.1-1 mm, significantly affect the transport of liquids within a given porous medium. Nuclear magnetic resonance imaging is used to probe the structure of porous catalyst support pellets, and four image analysis techniques characterize the degree and nature of heterogeneities observed in the spin-lattice relaxation-time images of six pellets taken from the same batch. Power-spectrum, cluster-size, and percolation analysis reveal significant differences in spatial correlations and topological characteristics of the six images. The fractal dimension of all the images, however, is the same suggesting that this quantity characterizes the intrinsic heterogeneities associated with the particular batch of porous pellets studied in this work. The results suggest that structural models of such pellets should account for these macroscopic variations in pellet structure, as characterized here.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410416
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690410401
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  • 148
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    Fractal nature of viscous fingering in two-dimensional pore level models (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 749-763 
    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: Use of saturation-dependent relative mobilities leads to linear flow; however, experiment and theory show that, in the limit of very large viscosity ratio, the flow is not linear but fractal. Generally, fractional flows and relative mobilities depend on both saturation and time. Use of a standard pore-level model of 2-D flow in the limit of infinite capillary number shows that this flow is fractal for large viscosity ratios (M = 10,000) and the sauration and fractional flows agree with the results of our general arguments. For realistic viscosities (M = 3 → 300), our modeling of the unstable flow shows that, although the flows are initially fractal, they become linear on a time scale, τ increasing as τ = τ0M0.17. Once linear, the saturation front advances as x ≈ v0M0.068 t; the factor M0.068 acts as a 2-D Koval factor.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410402
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  • 149
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    Novel method for noncontact measurement of particle temperatures (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 773-782 
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    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 nonintrusive temperature measurement technique is developed for noncontact measurement of the temperature of single particles with 〈 200 μm dia. It is based on the temperature dependence of the fluorescence spectrum resulting from irradiation of a certain phosphor mixture with UV light by applying a mixture of two phosphors with fluorescence colors (blue and green) and a color shift from green to blue (with temperature increase from 20 to 280°C). An experimental setup is described for temperature measurement of particles based on the fluorescence color, together with the calibration of this system. The fluoroptic technique is applied to measure the temperature decrease of hot particles flowing down a cold chute. The measurements agree very well with thermocouple measurements. This novel technique can be applied to nonintrusive measurement of particle temperatures in (dense) multiparticle systems as encountered in packed and fluidized beds.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410404
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  • 150
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    Editor's note on special section (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 948-948 
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    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 collection of articles in this special topical section were prepared based on presentations made at the 1993 Annual Meeting of AIChE. Theme of the session was the applications of molecular thermodynamics to problems of protein structures, solution properties, transport propertties, separations, and other issues important to chemical engineers in the biotechnology, biomedical, pharmaceutical and food industries. These articles were submitted to and survived the regular Journal reviewing procedure; they were grouped to highlight this important area with a concentration of articles similar to the special section we published last year on new imaging techniques. Further background on this subject is given in the following remarks bu Bramie Lenhoff and Mike Paulaitis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410422
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  • 151
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    Simple lattice model of proteins incorporating directional bonding and structured solvent (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 954-958 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410425
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  • 152
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    Binding of an antifreeze polypeptide to an ice/water interface via computer simulation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 959-973 
    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 interaction between a winter flounder antifreeze polypeptide and an ice/water interface was studied using Molecular Dynamics computer simulation techniques to study the mechanism of action of this class of antifreeze molecules. Simple Point Charge models were used for the water molecules, and a molecular mechanics program (CHARMM) was used to construct the model for the polypeptide. A (2021) face was exposed on the ice surface, as this is believed to be the experimentally favored ice face for peptide binding. The polypeptide binds strongly to the ice surface even though it was placed with its four polar threonine (Thr) groups pointing away from the ice surface. This tested the previously advanced hypothesis that adsorption occurs primarily between these groups and the ice due to a matching of the spacing between oxygen atoms in the ice lattice and the polar Thr residues. As well as contacts with other polar groups on the peptide, the binding to the ice produces a good steric fit of the peptide with the corrugated ice interface. The presence of the peptide did not induce any melting of the ice at 200 K.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410426
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  • 153
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    Continuum random walk simulations of diffusion and reaction in catalyst particles (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 880-893 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To predict the effect of pore structure on the performance of heterogeneous catalysts, a realistic model of the catalyst particle is required. Lattice-based models in which the diffusion and reaction phenomena are restricted to sites and bonds within a regular or irregular lattice are widely used. However, for the realistic simulation of diffusion and reaction in amorphous catalyst supports, such as alumina or silica, a continuum model, which does not artificially restrict the domain in which the reactants are allowed to diffuse, is required.An efficient method based on a “first passage time” approach is developed for the simulation of diffusion and reaction in a supported catalyst. The model catalyst is composed of spheres representing the support and active sites. By varying the algorithm used to generate the model catalyst, a range of structures can be created. The effect of the structure, and the size and distribution of active sites on the reaction rate is studied.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410415
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  • 154
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    Effects of operating conditions on stability of gas-phase polyethylene reactors (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 868-879 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluidized-bed polyethylene reactors are prone to unstable behavior and temperature oscillations (Choi and Ray, 1985b). Their work is extended to show the effects of ethylene feed system operation, reactor cooling system design, catalyst properties, and gas composition on reactor stability and dynamics. The analysis is performed using a well-mixed model, because heat- and mass-transfer resistances between multiple phases are small and are not required to account for the observed bifurcation phenomena. The addition of a gas recycle and heat exchanger system to the model significantly affects dynamic performance, including the formation of limit cycles. The size and dynamics of the heat exchanger, however, have little effect on the overall stability. In contrast, automation of the ethylene feed system to replace the monomer in the reactor as it is consumed leads to substantially different dynamic behavior than if the ethylene feed is maintained at a constant rate. Catalyst properties (multiple sites, activation energy, and deactivation) significantly affect dynamics and stability, whereas comonomer and other gases affect them only mildly. The results confirm that without proper temperature control, gas-phase polyethylene reactors are prone to instability, limit cycles, and excursions towards unacceptable high-temperature steady states.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410414
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690410201
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  • 156
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    Use of optical probes to characterize bubble behavior in gas-solid fluidized beds (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 223-228 
    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: Optical probes are used to study gas-solid fluidized-bed hydrodynamics. The probes each consisting of a light source and photodetector separated by a gap are suitable for use at combustion-level temperatures. The methodology to process the signal for calculation of bubble properties such as bubble frequency, local bubble residence time, bubble velocity, pierced length, bubble size, and visible bubble flow is presented. The signal processing technique is independent of bed operating conditions. The probe signal processing methodology is validated by comparing calculated bubble properties based on the probe signal with properties observed on videotapes of a 2-D bed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410204
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  • 157
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    Experimental measurements of pressure waves generated by impulsive heating of a surface (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 205-213 
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    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 first quantitative, reproducible experimental results are presented for the compressive wave generated in a gas by a rapid rise in the temperature of a bounding solid surface. When a resistive-capacitive electrical circuit rapidly heats a thin foil constituting one end of a closed polyacetal cylindrical tube to a high temperature, the amplitude of the initial traveling peak in pressure is proportional to the maximum rise in temperature of the heated surface and depends critically on the heating rate. This amplitude is twice as high for argon as for helium, and is intermediate and essentially the same for nitrogen and air. For all conditions, the wave celerity is slightly greater than the adiabatic acoustic velocity. The waves have a very sharp front and a long region of decay, which is contradictory to the sinusoidal waves postulated by Rayleigh and the nearly symmetrical ones predicted by all prior numerical solutions as well as by the asymptotic solution of Trilling. Such compressive waves and their reflections increase the transient heating rate of a confined gas, may produce unsuspected and unwanted disturbances in otherwise static systems, and offer a possible means of remote detection of excursions in the temperature of a surface.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690410202
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  • 158
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    Effect of long-range correlations on transport phenomena in disordered media (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 229-240 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three different flow and transport phenomena considered here are hydrodynamic dispersion in heterogeneous porous media and aquifers, transport of passive particles in an oscillating flow field, and miscible displacement processes in heterogeneous reservoirs. At microscales all three phenomena are described by the classical convective-diffusion equation (CDE). The presence of long-range correlations at macroscales gives rise to a rich variety of phenomena that cannot be predicted by analyzing the CDE by classical methods. In particular, a new percolation model with long-range correlations provides a rational explanation for the hitherto unexplained field-scale experimental data for hydrodynamic dispersion in porous media and aquifers. Moreover, for transport in oscillating flow in convection cells percolation provides a novel relation between the dispersion coefficient and the Péclet number that cannot be predicted by other methods.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690410205
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  • 159
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    Hindered settling of rod-like particles measured with magnetic resonance imaging (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 251-257 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Magnetic resonance imaging (MRI) is used to measure the time evolution of the volume fraction vs. height profile during batch sedimentation of rod-like particle suspensions. At any instant during sedimentation, MRI clearly delineates the supernatant, suspension, and sediment regions. The rod-like particles with a mean aspect ratio of 17.4 exhibit considerably larger hindered settling effects than spherical particles with increasing particle concentrations. This can be attributed in part to the larger increase in interparticle forces and relative viscosities with suspensions of rod-like particles than with suspensions of spherical particles, as the particle concentration increases. The relative viscosity of the rod-like particle suspensions is a function of the spin-spin relaxation time, T2. Since T2 is a measurable MRI quantity, this suggests that MRI may be used as an instrument for rheological measurement.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410207
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  • 160
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    Linear eddy modeling of reactant conversion and selectivity in turbulent flows (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 258-266 
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    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 linear eddy model (LEM) is used for statistical predictions of stationary, homogeneous turbulent flows under the influence of isothermal chemical reactions. Nonpremixed reacting systems are considered with two reaction mechanisms: a binary, irreversible single-step reaction A + B ↦ P; the series-parallel reaction A + B ↦ R, A + R ↦ P. In both systems, the influence of various flow parameters on the reactant conversion rate is elucidated. For the second reaction scheme, effects of the flow parameters on the “selectivity” are also investigated. The trends predicted by the LEM agree with those produced previously by direct numerical simulation (DNS) at moderate values of the Reynolds number, Schmidt number and Damköhler number. An important feature of the LEM is its capability to extend the parameter range well beyond that currently attainable by DNS. The LEM generated results for a wide range of Schmidt and Damköhler numbers are discussed as well as their effects on the selectivity. These results assess the performance of some of the existing closures for modeling of the selectivity. None of the closures are capable of reproducing the LEM results.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410208
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    Monte Carlo network simulation of horizontal, upflow and downflow depth filtration (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 272-285 
    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 test particle trajectory approach is developed for the simulation of deep bed filtration. A 3-D network of constricted pores represents the pore space of granular filters, network-scale trajectories of a large number of non-Brownian test particles are computed, and filter coefficient predictions are obtained for horizontal, down-and upflow filtration operation. This simulator yields numerical results that agree excellently with our earlier predictions by the pore-scale trajectory-based population balance method. The new approach, however, circumvents the cumbersome step of calculating the impacted fraction in each unit cell, which the earlier method required, by providing direct statistical estimates of the local and overall deposition rates for continuous and discrete pore-size distributions. For large superficial velocities (Vs 〉 ∼1 mm/s) and distributed pore size, downflow filters are more efficient than horizontal flow filters, whereas for small velocities (Vs〈 ∼ 0.5 mm/s) the opposite is observed. Horizontal flow operation is also favored by uniform packing for almost any value of the external pressure gradient. Upflow operation is the least efficient for the packings considered here over a broad range of superficial velocity and particle-size values. Observed differences among the three filtration types are maximal for uniform packings and decrease considerably with increasing packing heterogeneity.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410210
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    Droplet deposition and momentum transfer in annular flow (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2040-2046 
    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: Entrainment and deposition in gas-liquid annular upflow are known to account for as much as 20% of the pressure gradient, through droplet acclelerations in the core refion. Momentum is transerred from the core when droplets decelerate upon impactwith the liquid film. It is usually assumed that all of this momentum is transferred to the film, essentially driving the film upwardin conjunction with interfacial friction. New data, abtained for annular gas-liquid upflow in a 5.08-cm-ID tube, are used in a momentum balance analysis to determine the mechanismof momentum transfer from depositing droplets. Measurements include the liquid film thickness, wall shear stress, pressure gradient, entrained liquid fraction, droplet deposition rate, droplet centerline axial velocity, and mass-average drop size for two gas-liquid systems. This analysis supports the idea that large droplets displace the film locally and decelerate primarily at the wall, effectively transferring negligible momentum to the liquid film.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410904
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  • 163
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    Cross-flow ultrafiltration of micellar surfactant solutions (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2058-2066 
    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 Steady-state fouling-resistance and osmotic-pressure model is used to predict flux in the laminar, Cross-flow ultrafiltration of micellar cetyl ( =hexadecyl)pyridinium chloride (CPC) solutions at 0.01-M NaCl background electrolyte. The model assumes a constant overall hydraulic resistance including the effect of surfactant fouling and native membrane resistance. Measurements of osmotic pressures of CPC solutions at 0.01-M NaCl as a function of surfactant concentration describe the effect of concentration polarization on permeate flux. Two types of asymmetric polythersulfone membranes are used : 5,000 molecular weight cutoff (MWCO) membranes that allow partial monomer permeation, but quantitatively reject all micelles; 50,000 MWCO membranes that allow some micelle permeation. For the former, the intrinsic refection coefifient for monomer, measured separately, is sufficient to describe surfactant rejection, without adjustable parameters. Predictions of the volumetric flux of the permeate, including the value of the limiting flux, agree well with the experimental results over the entire range of pressure drop, axial velocity, and bulk surfactant concentration. For the 50,000 MWCO membrances, the data are described using a best-fit value of the overall surfactant rejection coefficient. For the first time, unusual behavior is observed experimentally in which the flux levels off with increasing pressure drop. Both effects are in accord with the proposed model. No gel layer need be postrulated to explain the flux behavior of either membrane type.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410906
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  • 164
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    A mechanistic analysis of sieve tray froth height and entrainment (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2067-2082 
    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: Phenomenologically based model for forth height was developed using the assumption of both vapor-and liquid-continuous zones within the total froth height. The model demonstrates the importance of liquid and vapor rates and determines that the Weber number (and therefore droplet size and surface tension) has little effect on froth height.A composite air/water database including entrainment data for both the spray and froth regimes is used to develop an entrainment correlation as a function of the ratio of tray spacing to froth height (Ts/h2φ) and the average froth density (φ2φ = hL).For conditions resulting in the ratio of liquid inventory to the perforation diameter (hL/dH) 〈4, the height, equation requires an empirical correction for froth height, and entrainment depends onφ2φ.This results from the predominantly vapor-continus nature of the froth. For large values of hL/dH, the theoretical value for h2φ appears adequate and entrainment is essentially independent of φ2φ, since most of the liquid is contained in the liquid-continuous region located far away from the underside of the tray above. In such cases, entrainment is from a light spray on top of the liquid-continuous region, and therefore entrainment depends much less on φ2φ.The differen dependency of entertainment on φ2φ can be used as a method to identify the spray-froth transition. For hL/dH〈2, a spraylikecondition exists; for hL/dH 〉 2, a frothlikecondition exists.The reported dependency of air/water system entrainment on major geometry and operating conditions is described well by the new correlation. Alternate correlations for the non-air/water entrainment data, however, are required. New methods for estimating the impact of entrainment on efficiency are given.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410907
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  • 165
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    Acetic acid oxidation and hydrolysis in supercritical water (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2108-2121 
    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: Acetic acid (CH3COOH) hydrolysis and oxidation in supercritical water were examined from 425 - 600°C and 246 bar at reactor residence times of 4.4 to 9.8 s. Over the range of conditions studied, acetic acid oxidation was globally 0.72 ± 0.15 order in acetic acid and 0.27 ± 0.15 order in oxygen to a 95% confidence level, with an activation energy of 168 ± 21 kJ/mol, a preexponential factor of 109.9 ± 1.7 and an induction time of about 1.5 s at 525°C. Isothermal kinetic measurements at 550°C over the range 160 to 263 bar indicated that pressure or density did not affect the rate of acetic acid oxidation as much as was previously observed in the oxidation of hydrogen or carbon monoxide in supercritical water. Major products of acetic acid oxidation in (upercriuical water are carbon dioxide, carbon monoxide, methaite, and hydrogen. Trace amounts of propenoic acid were occasionally detected. Hydrolysis or hydrothermolysis in the absence of oxygen resulted in approximately 35% conversion of acetic acid at 600°C, 246 bar, and 8-s reactor residence time. Regression of the limited hydrolysis runs assuming a reaction rate first-order in organic gave a global rate expression with a preexponential factor of 104.4 ± 1.1 and an activation energy of 94 ± 17 kJ/moL.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410910
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  • 166
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    Novel preparation techniques for thin metal-ceramic composite membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2131-2139 
    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: Composite metal membranes obtained by supporting thin metallic films on ceramic substrates have good thermal and mechanical stability. The use of a thin metal film increases transmembrane flux, while retaining high permselectivity that is characteristic of metallic membranes. Novel techniques have been developed for preparing metal-ceramic composite membranes. By the appropriate use of osmotic pressure, the microstructure, porosity, and thickness of the deposited metal can be systematically manipulated. Three new procedures are described for film densification and fabrication: (1) the osmotic pressure is used to densify an existing supported metal membrane; (2) densification and growth of the film is managed under the influence of osmotic pressure by using a dilute plating solution; and (3) films of varying porosity are deposited on the ceramic membrane by combining electroless deposition and osmotic pressure. Silver, palladium, and palladium-silver films prepared by these techniques on a commercial alumina membrane (Membralox) are thermally more stable than similar films deposited by conventional electroless plating.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410912
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690411001
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  • 168
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    Analysis of shear-dependent bacterial adhesion kinetics to biomaterial surfaces (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2160-2174 
    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 methodology and analysis is presented to quantitatively characterize bacterial attachment and detachment kinetics on biomaterial surfaces in a laminar flow field as a function of shear stress. The spatial distribution of adherent bacteria on the surface of a radial-flow chamber is monitored via automated videomicroscopy with motorized three-axis stage and focus control, allowing rapid automated measurement of the attached cell density as a function of time and radial position. Intrinsic rate constants for attachment and detachment are defined and estimated by fitting mathematical models to the resulting data. The model for cell attachment accounts for the global transport of cell in the chamber to estimate the cells concentration near the collector surface. The model for cell detachment accounts for heterogeneity in the adhesion energy of the attached cell population. These models yield first-order attachment and detachment rate constants that intrinsically reflect the probabilities of bacteria attachment and detachment as a function of applied shear stress, depending on only the local interactions between the cell and the surface. The validity of each model was tested by statistical analyses of the goodness-of-fit to data that resulted from a study comparing adhesion of Staphylococcus aureus to three different polymeric surfaces of Varying surface properties and adhesive protein coatings.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410915
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  • 169
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    Numerical computation of turbulent gas-solid particle flow in a 90° bend (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2187-2197 
    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 numerical computation of the LDV results of Kliafas and Holt is reported for a turbulent gas-solid particle flow in a square-sectioned 90° bend. A Eulerian model with generalized Eulerian solid surface boundary conditions for the particulate-phase momentum exchanges with solid walls are included. The turbulent closure is effected by using the gas-phase RNG-based k-∊ turbulence model, and the particulate turbulence diffusivity is related to the turbulent viscosity of the gas phase. Comparisons are made with experimental data for the mean streamwise velocities of both phases, the streamwise turbulence intensity of the gas phase, and the particulate concentration distribution in the bend. The localized high particulate concentration near the outer curve of the bend that occurs at large Stokes number is accurately predicted. Empirical computational evidence is presented for a relaxation of the minimum particle number density required to allow the use of a continuum model.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411003
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  • 170
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    Multiple roll systems: Residence times and dynamic response (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2198-2211 
    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: In roll coating as in other coating processes the coating liquid often suffers changes in properties on the time of the coating flow, that is, from fractions of a second upward depending on the amount of recirculation and recycling. The agents of change may be chemical reaction, colloidal aggregation, or evaporation. Hence the mean residence time and the residence time distribution of the liquid are important to designers and operators of coating processes. Here, building on the examination of roll-coating systems by Benjamin et al. (1995), the residence times of liquid coated by representative arrays of multiple rolls in the “forward roll” mode and relatively starved feed condition (neglecting the possibly significant effects of “rolling banks” and other internal recirculations when they are present) are analyzed. The dynamic response of these transfer coaters to step changes in the feed gap and to periodic gap changes, as from roll and bearing run-out, are also analyzed. No reports of operating or laboratory experiments are available for comparison. Nevertheless the results make plain how these quality-limiting features may depend don the number of rolls used; their sizes, speed, and arrangement, and the properties of the coating liquid.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411004
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  • 171
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    Analysis of multidimensional models of monolith catalysts for hybrid combustors (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2250-2260 
    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: Distributed parameter models of the single channel of a monolith combustor have been derived from progressively simplified assumptions. Simulation results are compared to assess the importance of the different physicochemical phenomena occurring in the combustor and to identify the simplest adequate model. For typical operating conditions of the hybrid combustor (gas and wall temperature not exceeding 1,073 and 1,273 K, respectively, high flow rate and pressure, natural gas as fuel), the results show that variations of gas properties have to be considered while homogeneous combustion can be neglected. Assumption of the approximate radial profile of axial velocity with invariant parabolic shape, rather than the rigorous solution of momentum balance and the continuity equation, provides accurate results. Moreover, for simulation of ceramic monoliths, backward heat transmission by wall conduction can be neglected with a substantial saving of computational labor.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411008
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  • 172
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    Wetting of fiber mats for composites manufacturing: II. Air entrapment model (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2274-2281 
    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: In this work the experimental observations are explained with the aid of a simple air-entrapment model based on the concept of two levels of porosity of fiber mats. A simple model that includes liquid bypassing with initial air trapping, subsequent capillary invasion of regular fiber bundles with air compression, and finally mobilization is proposed to explain air-entrapment phenomena. The simple model successfully rationalizes the observed air trapping and compression during initial liquid-fiber contact. An empirical equation for the mobilization efficiency is adapted to the model to estimate void content. The velocity dependence of the trapped void content predicted by the model is in good agreement with observations.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411010
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  • 173
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    Nitridation and CVD reactions with hydazine (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2282-2291 
    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 low-temperature nitridation of gallium arsenide, silicon and transition metals was investigated using hydrazine. Gallium nitride films were grown on gallium arsenide (GaAs) by direct reaction of the semiconductor surface layers with hydrazine et 200-400°C. Auger electron spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses show that the films are primarily gallium nitride with a small oxide impurity. Thin nitride films (∼15 Å) were grown on silicon by reaction with hydrazine at 300-500°C. Ellipsometry results suggest that the film growth goes through different phases following linear, parabolic and logarithmic functions with time. XPS analysis shows that the nitride films could be formed at much lower temperatures than possible with ammonia (300 vs. 600°C). The formation of numerous transition metal nitrides (Co, Cr, Fe, Mo, Si, Ta, Ti, V, and W) by reaction with hydrazine at 400°C is demonstrated, as well as the chemical vapor deposition of boron nitride films from diborane and hydrazine reactants. The temperature at the mixing point was critical in determining the final composition of the film. A 1-D transport model suggests that the reaction rate at 400°C was kinetically limited. The results also agree qualitatively with thermodynamic equilibrium calculations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411011
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  • 174
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    Second law analysis on fractal-like fin under crossflow (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2314-2317 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411015
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  • 175
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    Activity coefficients in nearly athermal model polymer/solvent systems (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2306-2313 
    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: Constant pressure Monte Carlo simulations were performed to study the activity coefficients of bead-spring polymers dissolved in a monomeric solvent. Activity coefficients were obtained for binary mixtures of monomer and 20-mer for compositions ranging from pure 20-mer to pure solvent, using the chain increment method to obtain the chemical potentials of long-chain solute and monomeric solvent. Infinite dilution activity coefficients were also calculated for polymeric solutes in monomeric solvents and monomeric solutes in polymeric solutes in monimeric solvents and monomeric solutes in polymeric solvents solutions with chain length up to 60. Such detailed information on activity coefficnets in polymer/solvent systems with large size differences had not been available previously from simulation or experiment. Several engineering models were tested for their ability to predict the activity coefficients in these nearly athermal systems. Results indicate that simple free-folume models can provide us with qualitatively accurate predictions for both short-chain solvent and long-chain solutes, provided that the functional form of the free-volume dependence is chosen appropriately.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411014
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    Application of multiresponse estimation to a wetted wall column model (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2327-2332 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411018
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    Isotope study on diffusion in CaSO4 formed during sorbent-flue-gas reaction (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2337-2340 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411020
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  • 178
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    Applied fluid mechanics by T. C. Papanastasiou, Prentice-Hall, Englewood Cliffs, NJ, 1994, 520 pp. (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2342-2342 
    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.690411022
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  • 179
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690411101
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  • 180
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    Rheology: Principles, measurements, and applications by C. Macosko, VCH Publishers, 1994, 550pp., $95.00 (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2344-2344 
    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.690411025
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  • 181
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    Newtonian drop impact with a solid surface (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1357-1367 
    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 spreading of Newtonian liquid drops after impact with a solid surface is reproted for a range of liquid and surface proeprties, drop diameters, and impact velocities. Results for liquid viscosities up to 300 mPa.s are given. For a given drop diameter and velocity, a range of liquid viscosities result in splashing even for smooth surfaces. The maximum spread radius, made dimensionless with the drop radius, is correlated as Rmax* = 0.61(Re2Oh)0.166, where Re and Oh are the Reynolds and Ohnesorge numbers. respectively. A model is proposed to account for inertial, viscous, and surface tension forces on the maximum spread radius. Good agreement is found between the model and experimental data from several sources.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410602
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  • 182
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    Properties of pulsing flow in a trickle bed (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2371-2382 
    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 of pulsing flow in trickle beds is presented, based on data from two measuring techniques. New evidence on pulse arrangement and propagation in the bed, and data on basic pulse characteristics (frequency, celerity, length, duration) as well as liquid holdup and pressure drop measurements are included. Some of these data, such as the length of the liquid-rich zone of pulses, are not currently available. Two flow regions exhibit different trends of pulse characteristics, “mild” and “wild” pulsing for relatively small and large liquid flow rates, respectively. New findings are compared with previously available data and correlations. An effort to develop new or modify existing generalized correlations is made for the aforementioned quantities.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411104
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  • 183
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    Fractional crystallization: Design alternatives and tradeoffs (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2427-2438 
    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: Guildlines for the design of fractional crystallization processes to separate two-and three-solute mixtures are presented. By using solvent addition/removal, stream combination, and cooling/heating, these processes bypass regions of multiple saturation in the phase diagram and recover purse solutes. Design equations are formulated, and the constraints on the design variables are identified. also included is a discussion of the effect on recyle flows of changes in the design variables and an estimate of the cost of a fractional crystallization separation.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411109
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  • 184
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    Maximum likelihood data rectification: Steady-state systems (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2415-2426 
    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 maximum likelihood rectification (MLR) technique that poses the data-rectification problem in a probabilistic framework and maximizes the probability of the estimated plant states given the measurements is proposed. This approach does not divide the sensors into “normal” and “gross error” classes, but uses all of the data in the rectification, each sensor being appropriately weighted according to the laws of probability. In this manner, the conventional assumption of no sensor bias is avoided, and both random errors (noise) and systematic errors (gross errors) are removed simultaneously. A novel technique is introduced that utilizes historical plant data to determine a peior probability distribution of the plant states. This type of historical plant information, which contains the physical relationships among the variables (mass balances, energy balances, thermodynamic constraints), as well as statistical correlations among the variables, has been ignored in prior data-rectification schemes. This approach can use the historical plant information to solve a new class of data-rectification problems in which there are no known model constraints. The MLR method is demonstrated on data from a simulated flow network and a simulated heat-exchanger network. The MLR technique provides considerably improved performance over existing data-reconciliation schemes in these examples.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411108
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  • 185
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    Modifications to model IV fluid catalytic cracking units to improve dynamic performance (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1481-1499 
    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: Model IV fluid catalytic cracking units (FCCUs) differ from other cracking units in that model IV FCCUs do not have slide valves in the catalyst circulation lines to enable direct control of catalyst circulation rate through the unit. Reducing fluctuations in catalyst circulation rate is found to significantly improve closed-loop performance of the FCCU. Some design and operational modifications that can be made to model IV FCCUs to improve closed-loop performance at the regulatory level based on this insight are modeled and compared. Closed-loop performance of a model IV FCCU operated with the weir and standpipe always flooded is examined. The achievable performance is significantly better thah that of the standard model IV FCCU. The closed-loop performance of the model IV FCCU modified to incorporate slide valves in the catalyst circulation lines is also examined. The performance of the FCCU with slide valves is better than the performance achievable by the FCCU with the weir flooded. It is found that model IV FCCUs are ill-conditioned owing to the use of the weir and standpipe arrangement in the regenerator section. Both the operational and design modifications studied reduce plant ill-conditioning appreciably.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410613
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  • 186
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    Reducing data dimensionality through optimizing neural network inputs (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1471-1480 
    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 neural network method for reducing data dimensionality based on the concept of input training, in which each input pattern is not fixed but adjusted along with internal network parameters to reproduce its corresponding output pattern, is presented. With input adjustment, a property configured network can be trained to reproduce a given data set with minimum distortion; the trained network inputs provide reduced data.A three-layer network with input training can perform all functions of a flue-layer autoassociative network, essentially capturing nonlinear correlations among data. In addition, simultaneous training of a network and its inputs is shown to be significantly more efficient in reducing data dimensionality than training an autoassociative network The concept of input training is closely related to principal component analysis (PCA) and the principal curve method, which is a nonlinear extension of PCA.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410612
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  • 187
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    Experimental and theoretical investigation of the validity of asymptotic lumped kinetics (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1513-1520 
    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: Continuum approximation is often used to treat problems involving reaction mixtures of a vast number of species. Previous studies predicted that in many situations the lumped kinetics of a continuum of reactions, regardless of their kinetics, are of the power law form after a long time. In this article we present experimental support for such asymptotic power law kinetics. The system considered is catalytic deep desulfurization of a petroleum distillate. In addition, a theoretical analysis is made to establish the condition under which the continuum approximation is valid in the long-time limit. The condition turns out not to be very stringent for practical purposes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410615
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  • 188
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    Continuous kinetics for thermal degradation of polymer in solution (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1521-1533 
    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: Continuous kinetics of thermal degradation of poly (styrene-allyl alcohol) (PSA) in solution are explored theoretically and experimentally. Thermal degradation experiments for PSA of number-average molecular weight 1,640 in t-butanol solution were conducted in a steady-state flow reactor at 6.8 MPa and 403-473 K. The molecular-weight distributions (MWDs) of the original polymer and its reaction products were measured as a function of residence time by gel permeation chromatography The MWD of the initial PSA is described by a gamma distribution function. Experimental data indicated that the polymer cracks to specific, low-molecular-weight (MW) products and degrades by random chain scission. Results are interpreted by a mathematical model based on the continuous kinetics for specific and random degradation processes. Rate coefficients are determined separately from the dynamic data of the MW moments for the specific products and the MWDs for the reacting polymer. Activation energies obtained are 5.9 - 7.4 kcal/mol for specific degradation processes and 35 kcal/mol for the random degradation process. The detailed MWDs are related to conventional lumped (numberaverage molecular-weight) data.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410616
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  • 189
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    Mechanistic description and experimental studies of electrochromatography of proteins (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2499-2507 
    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: Electrochromatography is a form of gradient liquid chromatography in which an axial electric potential is applied to columns packed with gel-filtration media. Experimental methodology and a mechanistic model are further developed for a system that minimizes Joule heating at electric field strengths of 100 V/cm by dissipating heat through a cooling jacket and use of a cooled, low ionic strength eluting buffer. Focusing of proteins can be achieved in a 15-mm-dia. Column by the interplay of eluent velocity, electrophoretic migration rate, and electrically induced concentration polarization when the stationary phase is more conductive than the mobile phase. Voltage gradients of up to 125 V/cm for eluent velocities at 18-25 cm/h separate binary protein mixtures of Bhb-α-lactalbumin, BSA-myoglobin, and α-lactalbumin-myoglobin over Sephadex G-100 and G-50. Retention times are consistent with values obtained from a mechanistic nonlinear model.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411115
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  • 190
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    Turbulent flow in channels in terms of turbulent shear and normal stresses (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2513-2521 
    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 local time-averaged velocity, the mixed-mean velocity, and the friction factor for fully turbulent flow between parallel plates and in round tubes and concentric circular annuli can be expressed in terms of integrals of the turbulent shear stress, The pressure distribution across a channel can similarly be expressed in terms of an integral of normal stresses. These formulations, which are simple and exact, can be integrated numerically using experimental data, compyted values, or correlating equations for turbulent stresses. Their greatest merit, however, may arise from the insight they provide with respect to the contributions of the fluctuating components of the velocity. For example, for concentric circular annuli such a formulation identifies a difference between the locations of the maximum in the velocity and the zero in the total shear stress. This difference, which has been overlooked in most experimental and semitheoretical investigations, introduces an error of unknown but possibly significant magnitude into all of the results. It also precludes the application of the mixing-length, eddy viscosity and k - ∊ models.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411202
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  • 191
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    Electrochemically modulated complexation process for gas removal and concentration (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2556-2564 
    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 electrochemically modulated complexation process was designed to extract and concentrate a gas-phase solute. The process was based on flowthrough electrolysis cells that electrochemically modulate a liquid-phase mass-transfer agent between high and low solute affinity forms. The liquid phase in the high-affinity form contacts a feed gas phase for the extraction and contacts the receiving gas phase in the low-affinity form. The chemical system used to demonstrate the general process was a Cu(II)/Cu(I) redox couple in an acidic chloride electrolyte to both concentrate carbon monoxide against a pressure gradient and selectively separate it from a mixture with nitrogen. Experimental results and modeling of this process are reported. The kinetics of the electrolysis reactions in the flow cells are discussed within the context of rotating ring disk voltammetry experiments.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411206
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  • 192
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    Potentialities and limitations of mixing simulations (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1605-1621 
    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: As numerical simulations in mixing become pervasive, an analysis of errors becomes crucial. Purposely discretized examples with exact analytical solutions provide a reference point from which to judge the soundness of numerical solutions. Three types of errors are identified and examined: discretization, time integration, and round-off, with emphasis on the first two. Theoretical derivations and numerical examples for 2-D, steady (regular) and time-periodic (chaotic) flows indicate that errors, in general, behave as material lines. In regular flows, their magnitude increases, on the average, with at most t2, while in chaotic flows it increases exponentially. Errors tend to align with the direction of the streamlines in regular flows and with manifolds in chaotic flows. As a result, even though exact and calculated trajectories diverge exponentially fast in chaotic flows, overall mixing patterns are reproduced, at least qualitatively, even when the velocity field is calculated using the main features of a line as it is deformed by the flow, although the error in its length may be more than 100%. It is concluded that accurate quantitative information, such as the location of periodic points or the length of a deformed line, can be obtained from numerical simulations. However, robust application of standard numerical analysis tools, such as mesh refinement, is necessary, which, in turn, can lead to nearly prohibitive computational costs.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410702
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  • 193
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    Experimental investigation of the polymer melt flow during injection post-filling process (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2661-2663 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411217
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  • 194
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    Foamed gel barriers in porous media: Breakdown and permeability evolution (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2487-2498 
    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: Foamed del has begun to play an important role in permeability modification applications because of the reduced chemical requirements. Foamed gels create impermeable barriers in porous media; however, once a critical pressure differential is exceeded, the permeability increases with increasing pressure. A two-dimensional network model was developed to estimate foamed gel barrier performance in terms of the maximum pressure a barrier can withstand and the evolution of the foamed gel barrier's permeability. The formation of conductive pathways and the accopanying permeability increase were estimated from a model of the pressure-induced deformation and repture of individual lenses. The evolution of conductive pathways changed from invasion percolation (high elastic modulus, rigid gel) to a lens rupture chain reaction initiated by teh rupture of a single lens (low elstic modulus gel) as the elastic modulus of the gel was decreased. The apparent fractal dimension of the first conductive channel ranged from 1.89 to 1.06 for high and low wlastic modulus gels, respectively. This dependency of breakthrough and breakdown is unique and produces a large range of breakdown behavior for any degree of microscopic heterogeneity.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411114
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  • 195
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    Masthead (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995) 
    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.690411201
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  • 196
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    Mixing, reaction, and precipitation: Interaction by exchange with mean micromixing models (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2537-2548 
    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 of interaction by exchange with the mean micromixing model is extended to a process involving elementary chemical reaction between two species and subsequent crystallization of product in a continuous mixed suspension mixed product removal etystallizer. Two specific feed conditions are considered: premixed and anpremixed feeds are considered. The sensitivity of these two cases to several parameterv like the Damköhler number, micromixing parameter, fractional flow rate, and dimensionless inlet concentration of excess reactant is explored. Both reaction and crystallizaLion performance characteristics are significantly influenced by the fred conditions. Results for the case of premixed feeds tend to suggest that the model description may be better suited to a nearly segregated configuration.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411204
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  • 197
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    Binary kinetics in the Y-Ba-Cu system: 1. Mixed powders (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1779-1789 
    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 kinetics of the reactions between mixed powders BaCO3 and CuO, as well as BaCO3 and Y2O3, have been studied using DXRD techniques as a function of particle size, temperature, and CO2 pressure. Except for intial nucleation phenomena, the reaction ration rates are governed by shrinking core bahavior for BaCO3 particle sizes between 6 and 33 μm. During the initial stages of the reactions, the surface reaction kinetics are gare governing, whereas the diffusion of CuO, Y2O3, and CO2 are limiting factors at later stages in the reactions. Quantitative conversion dat were used to determine the values of the activation energies and the pertinent diffucivities in these systems.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410713
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  • 198
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    Eddy diffusivity of solid particles in a turbulent liquid flow in a horizontal pipe (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1815-1820 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410716
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  • 199
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    Stagnant film model for effect of diffusional layer thickness on heat transfer and exerted friction (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1821-1825 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410717
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  • 200
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    Binary kinetics in the Y-Ba-Cu system: 2. Nanosized particles (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1790-1797 
    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 kinetics of binaty mixtures of Y2O3 - BaCO3-CuO (Ba-Cu) and Y2O3 -CuO(Y-Cu) prepared by citrate sot-gel techniques were studied in both air and helium. Particle sizes resulting from the sol - gel preparation were between 5 and 100 nm, and the prevailing kinetics differed significantly from those observed in the companion study of micron-sized particles. That is, nucleation-growth kinetics of the Avrami-Erofe'eu type adequately model the kinetics over the entire conversion range as opposed to the diffusion mechanisms that describe the kinetics in larger sized particles. An alternate nucleation-growth model, which neglects overlapping volumes during reaction (Austin - Rickett model), was also adequate in the Ba-Cu system where particle size/spacing was larger, but was only applicable in other reaction systems at lower conversions. Activation energies obtained from the Avrami- Erofe'ev were consistently lower than those from the Austin - Rickett model, because the former model contains two parameters that are temperature-sensitive.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410714
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