Frictional Drag Reduction and Mechanical Degradation of Dilute Polyethylene Oxide Solutions in High Shear Turbulent Flow Environments PDF Download
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Author:
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Category : Dissertations, Academic
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages :
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Author: T. T. Huang
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ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 36
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Book Description
Drag reduction caused by dilute polyethylene oxide (POLYOX WSR-301) and anionic charged polyacrylimide (MAGNIFLOC 835A) polymer solutions was studied experimentally in 1.918- and 0.455-cm ID smooth pipes. The POLYOX solutions tested are superior in drag reduction but inferior in shear-degradation resistance compared to the MAGNIFLOC solutions at corresponding concentrations. A three-layer mean velocity profile model appears to be more consistent with current and other data than a traditional two-layer model. The onset of measured drag reduction depends upon solution concentration and is seriously affected by shear degradation. (Author).
Author: Ira Michael Felsen
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 286
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The study was initiated to investigate turbulent flow drag-reduction by dilute poly(ethylene oxide) solutions in capillary tubes and thereby elucidate the mechanism of drag-reduction through interpretation of the experimental results. Flow through capillary tubes was chosen as a means to (1) obtain a large ratio of solid surface area to fluid volume, and (2) obtain high shear stresses at low Reynolds numbers. This allowed investigation of surface effects and polymer degradation as a function of a number of variables which are known to influence drag-reduction. (Author).
Author: P.I. Gold
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Category :
Languages : en
Pages : 167
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Author: Paul Peyser
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ISBN:
Category :
Languages : en
Pages : 20
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The frictional drag reduction of high-molecular-weight polyethylene oxide and polystyrene solutions under turbulent flow conditions was studied as a function of temperature, solvent power, and solvent viscosity. A rotating disk apparatus was used to make the drag reduction measurements. For aqueous polyethylene oxide solutions, at concentrations well above that needed to produce maximum drag reduction, all drag reduction data reduced to a common curve when percent drag reduction was plotted against the Reynolds number for the flow. However, for polyethylene oxide solutions below this optimum concentration the drag reduction-versus-Reynolds number curves showed decreasing drag reduction with increasing temperature. The data are explained primarily in terms of the inverse temperature solubility characteristics of polyethylene oxide in water. The percent drag reduction of polystyrene in nonaqueous liquids was found to be greater in good solvents than in poor ones. It was also found that increases in solvent viscosity and decreases in temperature increased the percent drag reduction. The results are discussed in relation to the current drag reduction theories and are shown to be in opposition to Virk's theory. It is concluded from the data that drag reduction is very likely a function of a relaxation time phenomenon involving the polymer molecules and the flow system. The results also emphasize the importance of considering solvent power, viscosity, and temperature in the design of an efficient drag reduction system. (Author).
Author: A. T. Ellis
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ISBN:
Category :
Languages : en
Pages : 8
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Book Description
The drag reducing properties of two dilute polymer solutions were studied using a simple turbulent pipe flow apparatus under various conditions of storage and mechanical degradation. Aqueous solutions of Polyox WSR-301 (polyethylene oxide) and Separan AP-30 (polyacrylamide) were prepared at 500 PPMW and then diluted into weak concentrations for storage and testing on a day by day basis. Data which display the friction reducing effectiveness as a function of aging and repeated shear degradation are presented for both polymers. At concentrations of 10, 25, 50 and 100 PPMW, aged samples showed the same 'peak' effectiveness as freshly prepared ones. However, the aging process reduced all the ability to resist mechanical degradation. Anomalies were found in which solutions tend to partially recover from shear degradation under certain conditions, and in other cases tend to improve their friction reducing efficiency after continuous shearing. Experimental results suggest that entanglement or aggregation of polymer molecules could be one of the important mechanisms involved in friction reduction. (Author).
Author: Hyunkook Shin
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 590
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Book Description
The object of this thesis was to investigate the drag reduction phenomenon in turbulent flow caused by random coiling macromolecules in 'dilute' solution. In particular, this thesis was concerned with the relationship of drag (or its reduction) to the size of the coils and their concentration, of two kinds of polymers differing significantly in chain flexibility: polyethylene oxide (PEO), the more flexible, and polyisobutylene (PIB), the less flexible. It was found that, within any given homologous polymer series, the ability of macromolecules to reduce drag improved drastically with increasing molecular weight. That is, the concentration of polymers in solution either in the absolute weight fraction or in the effective volume fraction required to yield a given percent drag reduction decreased rapidly with increasing molecular weight. It was further found that there always existed an optimum concentration for any given polymer system at which the observed drag reduction reached a maximum.
Author: Robert W. Paterson
Publisher:
ISBN:
Category :
Languages : en
Pages : 197
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The purpose of the study was to attempt to find an explanation for the phenomenon first reported by Toms in 1948 in which the addition of a few grams of a long chain polymer to a million cubic centimeters of a Newtonian solvent caused a large decrease in the turbulent pipe flow pressure drop while causing only a small increase in the laminar flow viscosity. This phenomenon, which has been observed to occur for a number of different polymers and solvents, is commonly referred to as 'drag reduction with dilute polymer solutions' or 'the Toms phenomenon'. (Author).
Author: Xin Zhang
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Category :
Languages : en
Pages :
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Book Description
Flow friction reduction by polymers is widely applied in the oil and gas industry for flow enhancement or to save pumping energy. The huge benefit of this technology has attracted many researchers to investigate the phenomenon for 70 years, but its mechanism is still not clear. The objective of this thesis is to investigate flow drag reduction with polymer additives, develop predictive models for flow drag reduction and its degradation, and provide new insights into the drag reduction and degradation mechanism. The thesis starts with a semi-analytical solution for the drag reduction with polymer additives in a turbulent pipe flow. Based on the FENE-P model, the solution assumes complete laminarization and predicts the upper limitation of drag reduction in pipe flows. A new predictive model for this upper limit is developed considering viscosity ratios and the Weissenberg number - a dimensionless number related to the relaxation time of polymers. Next, a flow loop is designed and built for the experimental study of pipe flow drag reduction by polymers. Using a linear flexible polymer - polyethylene oxide (PEO) - in water, a series of turbulent flow experiments are conducted. Based on Zimm's theory and the experimental data, a correlation is developed for the drag reduction prediction from the Weissenberg number and polymer concentration in the flow. This correlation is thoroughly validated with data from the experiments and previous studies as well. To investigate the degradation of drag reduction with polymer additives, a rotational turbulent flow is first studied with a double-gap rheometer. Based on Brostow's assumption, i.e., the degradation rate of drag reduction is the same as that of the molecular weight decrease, a correlation of the degradation of drag reduction is established, along with the proposal of a new theory that the degradation is a first-order chemical reaction based on the polymer chain scission. Then, the accuracy of the Brostow's assumption is examined, and extensive experimental data indicate that it is not correct in many cases. The degradation of drag reduction with polymer additives is further analyzed from a molecular perspective. It is found that the issue with Brostow's theory is mainly because it does not consider the existence of polymer aggregates in the flow. Experimental results show that the molecular weight of the degraded polymer in the dilute solution becomes lower and the molecular weight distribution becomes narrower. An improved mechanism of drag reduction degradation considering polymer aggregate is proposed - the turbulent flow causes the chain scission of the aggregate and the degraded aggregate loses its drag-reducing ability. Finally, the mechanism of drag reduction and degradation is examined from the chemical thermodynamics and kinetics. The drag reduction phenomenon by linear flexible polymers is explained as a non-spontaneous irreversible flow-induced conformational-phase-change process that incorporates both free polymers and aggregates. The entire non-equilibrium process is due to the chain scission of polymers. This theory is shown to agree with drag reduction experimental results from a macroscopic view and polymer behaviours from microscopic views. The experimental data, predictive models, and theories developed in this thesis provide useful new insights into the design of flow drag reduction techniques and further research on this important physical phenomenon.
