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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 37 (1996), S. 663-670 
    ISSN: 1436-2449
    Keywords: porous media ; polyacrylamide ; mechanical degradation ; opposed jets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work we present an experimental study of flow-induced degradation of hydrolyzed polyacrylamide in aqueous solutions flowing through porous media. The degradation is analyzed by passing the solution repeatedly through the medium at a constant flow velocity and the degraded solution is then characterized by porous media and opposed jets flows. When the polyacrylamide is dissolved in deionized water, it exhibits a gradual extension thickening in the flow through porous media and opposed jets. In this case, the polymer degrades as it passes through the porous medium even at relatively low flow rates. When the polyacrylamide is dissolved in an NaCl solution, it exhibits critical extension thickening in porous media flows, and it only degrades at Reynolds numbers that are higher than the onset of the extension thickening behavior. Chain degradation is therefore only encountered when extension thickening is produced. The results also show that the extent of degradation decreases as the pore size decreases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-2449
    Keywords: Keywords: Porous media flow ; Poly(ethylene oxide) ; Sodium Dodecyl Sulfate ; Polymer/Surfactant Mixtures ; Transient networks.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work, the porous media flow of solutions of mixtures of Poly(ethylene oxide), PEO, and Sodium Dodecyl Sulfate, SDS, was studied. Aqueous solutions of PEO exhibited the well known critical extension thickening effect when flowing through disordered packings of glass spheres. Upon addition of SDS to a solution of fixed PEO concentration, the extension thickening of the mixture exhibits a maximum as a function of SDS concentration that mimics the shear viscosity behavior of the polymer-surfactant mixture. However, when NaCl is added to the mixture, higher extension thickening effects at relatively low SDS concentrations were detected, in spite of the fact that the shear viscosity of the mixtures was about the same as that of equivalent PEO/SDS solutions in deionized water. The results were rationalized in terms of how the formation of SDS micellar aggregates along the PEO chain can alter the ability of the polymer to form transient entanglement networks, which is the cause of the extension thickening behavior.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 33 (1994), S. 717-724 
    ISSN: 1436-2449
    Keywords: Polymer blends ; porous media ; molecular flexibility ; hydroxypropyl guar ; poly(ethylene oxide)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In flow through porous media, solutions of poly(ethylene oxide) (PEO) exhibit extension thickening, whereas hydroxypropyl guar (HPG) solutions are shear-thinning at high concentrations. The results show that the extension-thickening exhibited by PEO solutions becomes less critical with increasing flow rate as the concentration of HPG in the solution is increased. At high concentrations of HPG, the presence of PEO inhibits the shear-thinning behaviour, without increasing the apparent viscosity of the solution. The presence of HPG reduces the rate and extent of degradation of PEO in the flowing solution.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 36 (1996), S. 111-118 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work we explore the effect of a cross-linking agent on the drag reduction capability of hydroxypropyl guar and guar gum solutions in turbulent flow through horizontal pipes. The results show that the addition of a cross-linking agent (borax) to solutions with concentrations below those required for gel formation enhances drag reduction due to the increased dimensions of the macromolecules in the presence of intermolecular cross links. The flow-induced degradation of the polymers is not appreciably affected by the addition of cross-linking agent.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 272 (1994), S. 1224-1233 
    ISSN: 1435-1536
    Keywords: Porous media ; monodisperse polystyrene ; elongational viscosity ; entanglements ; elongational flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this work, we study the origin of the extension thickening commonly observed when solutions of flexible polymers flow through porous media and ideal elongational flows. We have used randomly packed beds of glass beads as porous media. We have performed experiments with closely monodisperse atactic polystyrene of different molecular weights dissolved in organic solvents. The use of a closely monodisperse polymer allowed us to make a more meaningful comparison between the results obtained using opposed jets and porous media flow, as compared to previous works on polydisperse polymers. The results indicate that the coil-stretch transition of isolated polymer molecules in solution cannot be the only mechanism responsible for the extension thickening. It is clear that part of the observed effect is due to the extension of isolated molecules, but the main factor causing a great increase in the elongation viscosity beyond a critical strain rate is the formation of transient entanglement networks.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 6 (1991), S. 143-157 
    ISSN: 1573-1634
    Keywords: Diffusion ; effective diffusivity ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Calculations of effective diffusivities in three-dimensional, spatially periodic porous media are performed. For isotropic systems, it is found that, for a given porosity, the predicted value of the effective diffusivity matches experimental results for randomly-packed beds of spheres. Furthermore, the three-dimensional geometry yields approximately the same results as previous calculations employing two-dimensional representations, indicating a relative insensitivity of the effective diffusivity to local geometry. Regarding anisotropic systems, for which two-dimensional modes fail, it is found that there is a significant improvement in the prediction of the effective diffusivity perpendicular to the bedding plane when the three-dimensional model is employed using one adjustable parameter. However, the three-dimensional model overestimates the effective diffusivity parallel to the bedding plane.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 4 (1989), S. 213-238 
    ISSN: 1573-1634
    Keywords: Multiple scales ; double porosity ; heterogeneous porous media ; multiphase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The macroscopic equations that govern the processes of one- and two-phase flow through heterogeneous porous media are derived by using the method of multiple scales. The resulting equations are mathematically similar to the point equations, with the fundamental difference that the local permeabilities are replaced by effective parameters. The method allows the determination of these parameters from a knowledge of the geometrical structure of the medium and its heterogeneities. The technique is applied to determine the effective parameters for one- and two-phase flows through heterogeneous porous media made up of two homogeneous porous media.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1758-1762 
    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: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1733-1736 
    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
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1333-1336 
    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
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