An Experimental Study of Drag and Heat Transfer Reductions in Turbulent Pipe Flows for Polymer and Surfactant Solutions PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download An Experimental Study of Drag and Heat Transfer Reductions in Turbulent Pipe Flows for Polymer and Surfactant Solutions PDF full book. Access full book title An Experimental Study of Drag and Heat Transfer Reductions in Turbulent Pipe Flows for Polymer and Surfactant Solutions by Guillermo Aguilar-Mendoza. Download full books in PDF and EPUB format.
Author: Guillermo Aguilar-Mendoza
Publisher:
ISBN:
Category :
Languages : en
Pages : 363
Get Book Here
Book Description
Author: Guillermo Aguilar-Mendoza
Publisher:
ISBN:
Category :
Languages : en
Pages : 363
Get Book Here
Book Description
Author: Feng-Chen Li
Publisher: John Wiley & Sons
ISBN: 1118181115
Category : Science
Languages : en
Pages : 233
Get Book Here
Book Description
Turbulent drag reduction by additives has long been a hot research topic. This phenomenon is inherently associated with multifold expertise. Solutions of drag-reducing additives are usually viscoelastic fluids having complicated rheological properties. Exploring the characteristics of drag-reduced turbulent flows calls for uniquely designed experimental and numerical simulation techniques and elaborate theoretical considerations. Pertinently understanding the turbulent drag reduction mechanism necessities mastering the fundamentals of turbulence and establishing a proper relationship between turbulence and the rheological properties induced by additives. Promoting the applications of the drag reduction phenomenon requires the knowledge from different fields such as chemical engineering, mechanical engineering, municipal engineering, and so on. This book gives a thorough elucidation of the turbulence characteristics and rheological behaviors, theories, special techniques and application issues for drag-reducing flows by surfactant additives based on the state-of-the-art of scientific research results through the latest experimental studies, numerical simulations and theoretical analyses. Covers turbulent drag reduction, heat transfer reduction, complex rheology and the real-world applications of drag reduction Introduces advanced testing techniques, such as PIV, LDA, and their applications in current experiments, illustrated with multiple diagrams and equations Real-world examples of the topic’s increasingly important industrial applications enable readers to implement cost- and energy-saving measures Explains the tools before presenting the research results, to give readers coverage of the subject from both theoretical and experimental viewpoints Consolidates interdisciplinary information on turbulent drag reduction by additives Turbulent Drag Reduction by Surfactant Additives is geared for researchers, graduate students, and engineers in the fields of Fluid Mechanics, Mechanical Engineering, Turbulence, Chemical Engineering, Municipal Engineering. Researchers and practitioners involved in the fields of Flow Control, Chemistry, Computational Fluid Dynamics, Experimental Fluid Dynamics, and Rheology will also find this book to be a much-needed reference on the topic.
Author: A. Gyr
Publisher: Springer Science & Business Media
ISBN: 9401712956
Category : Technology & Engineering
Languages : en
Pages : 243
Get Book Here
Book Description
Drag Reduction of Turbulent Flows by Additives is the first treatment of the subject in book form. The treatment is extremely broad, ranging from physicochemical to hydromechanical aspects. The book shows how fibres, polymer molecules or surfactants at very dilute concentrations can reduce the drag of turbulent flow, leading to energy savings. The dilute solutions are considered in terms of the physical chemistry and rheology, and the properties of turbulent flows are presented in sufficient detail to explain the various interaction mechanisms. Audience: Those active in fundamental research on turbulence and those seeking to apply the effects described. Fluid mechanical engineers, rheologists, those interested in energy saving methods, or in any other application in which the flow rate in turbulent flow should be increased.
Author: Xin Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Since the discovery of the drag reduction effects of even small amount of macromolecules in solutions in turbulent pipe flows, there have been many experimental and theoretical studies in order to understand mechanisms behind this phenomenon. Theories have been proposed based on the observations on the change in the characteristics of the turbulent flow near the pipe wall where friction of the momentum transfer between the flow and the conduit takes place. In this study drag reduction in fully developed turbulent pipe flow with four concentrations (200 to 500 wppm) of low molecular weight Sodium Carboxymethylcellulose (CMC) in aqueous solutions was investigated experimentally. Drag reduction was determined by pressure drop measurements. In order to observe the impact of the presence of CMC on the flow, Ultrasound Doppler Velocimetry (UDV) was employed to monitor the instantaneous velocity distributions. UDV is a non-invasive technique allowing one to obtain quick velocity profiles. Experimental measurements were used to calculate Fanning friction factor and radial distributions of the axial time-averaged velocity, velocity fluctuation (turbulent intensity) and eddy viscosity. The drag reduction level was determined through the Fanning friction factor versus Reynolds number data. Velocity data could be obtained as close as 3 mm to the wall by UDV. Two impacts of increasing CMC concentration on the flow field, hence pressure drop, were observed. The first effect was the decrease of the mean velocity gradient especially near the wall with increasing polymer amount which in turn gave rise to lower friction factor or pressure drop. In addition smaller eddy viscosities were obtained in the flow. The second impact of the polymer addition was on the velocity fluctuation or turbulent intensity variation along the radial distribution. An increasing trend in turbulence intensity in the turbulent core with polymer addition was observed. This was in agreement with the earlier st.
Author: Robert H. J. Sellin
Publisher:
ISBN:
Category : Boundary layer control
Languages : en
Pages : 360
Get Book Here
Book Description
Author: Larry Gregg Chorn
Publisher:
ISBN:
Category :
Languages : en
Pages : 482
Get Book Here
Book Description
Author: Geoffrey William Holman
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
Get Book Here
Book Description
Author: Herbert Simon Stephens
Publisher: Bhra Fluid Engineering
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 378
Get Book Here
Book Description
Author: Ross Bradley Chongson
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 0
Get Book Here
Book Description
Drag reduction (DR) by additives typically involves the use of either high molecular weight polymer or surfactants, and can reduce turbulent pressure losses in pipes by up to 90%. These additives, particularly high polymers, have seen considerable use in increasing the throughput of crude oil pipelines. Surfactant additives, while even more effective than their polymer cousins, have not seen widespread adoption despite their applicability to recirculating district heating or cooling networks. Due to their effects on the turbulent structure of pipe flow, drag reducing additives also result in the loss of radial mixing, and thus the suppression of convective heat transfer. This is referred to as the 'heat transfer reduction' (HTR) effect. Under normal conditions, drag reducing additives can reduce convective heat transfer in even greater amounts than they do turbulent pressure losses. Much of the recent research in the field of surfactant drag reduction has, therefore, been dedicated to the mitigation of heat transfer reduction. In this work, two projects are presented which successfully achieve this goal. In the first, a constricted heat exchanger is used to locally increase the shear stresses experienced by the working fluid. Simultaneously, a `weak' drag reducing solution comprised of quaternary ammonium salts with saturated tails 16 and 14 carbons in length and the counterion 3-chlorobenzoic acid. In conjunction with the constricted heat exchanger, this mixture is able to simultaneously generate high (>60%) DR and low (>30%) HTR over a range of flow rates and temperatures. Other unique properties of the system are examined, including switchability and hysteresis. The second study involves the design and application of 'gentle' static mixers. Rather than being designed to destroy the micellar structure thought to be responsible for DR, these mixers are intended to periodically disrupt the thermal boundary layer in the heat exchanger, thus improving heat transfer. Two designs are examined: a finned mixer and a double-helical mixer, both capable of reducing HTR to 30% from a high of 90%. Design considerations were discussed, as well as future goals to further extend the work.
