bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Adding Phosphate on the Size of Extremely Fine Needle‐like Lepidocrocite Particles Prepared by Oxidizing an Aqueous Suspension of Ferrous Hydroxide
Authors: Mihara Naoki , Kawasaki Hiroyuki , Kumazawa Hidehiro , Choi Woo‐Sik , Kwak Jung‐Sup , Choi Hee‐Kyu 
Published: July 2010

AbstractExtremely fine particles of needle‐like lepidocrocite (γ‐FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature of 30°C, and the effects of the reaction conditions or the oxidation rate were investigated in order to determine the parameters that control the particle size. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of a needle‐like particle decreased from 0.7 µm to 0.4 µm with increasing oxidation rate. By adding of NaH2PO4 to an aqueous Fe(OH)2 suspension, in concentrations up to 1.0 mol/m3 during the air oxidation, and up to 0.9 mol/m3 during the oxidation with 30% and 50% O2, the major axis could be reduced to ca. 0.3 µm with the minor axis and the oxidation rate remained almost unchanged.
Settling Velocities of Polydisperse Concentrated Suspensions
Authors: Ha Zhanyao , Liu Shijie 
Published: July 2010

AbstractA model for particle settling velocities in polydisperse suspensions is proposed alongside normalized particle self and interaction mobilities. The model predictions are compared with other models (Davis and Gecol, 1994; and Al‐Naafa and Selim, 1989), as well as published experimental data. A general agreement was found between the current model and the existing data for binary dispersed particle systems except for one case where ΦL is fixed. For ternary dispersed particle systems, predictions from both the A‐S model and the current model agree well with the existing data. With the improved sedimentation coefficients, the D‐G model also produces satisfactory results.
Some Issues on Core‐Annulus and Cluster Models of Circulating Fluidized Bed Reactors
Authors: Bi Hsiaotao T. 
Published: July 2010

AbstractThe one‐dimensional cluster model and the core‐annulus model are examined based on existing correlations. The core‐annulus model is found to give reasonable agreement with ozone decomposition data when the effective interphase mass transfer rate constant is equal to about 0.1 1/s, which is one order smaller than the reported values based on gas tracer tests. The prediction from the core‐annulus model that the reactor performance decreases with increasing the riser diameter is found to be inconsistent with limited experimental data The one‐dimensional cluster model predicts that a riser reactor performs very close to the pseudo‐homogeneous plug flow reactor because of the high mass transfer rate between the cluster and the dilute phase. The improvement of model predictions lies in the better characterization of the cluster shape, size and the mass transfer rate between the cluster and the dilute phases.
Modelling the Effective Thermal Conductivity in Polydispersed Bed Systems: A Unified Approach using the Linear Packing Theory and Unit Cell Model
Authors: Gupta Murlidhar , Yang Jin , Roy Christian 
Published: July 2010

AbstractA comprehensive, unified approach, using the Linear Packing Theory and Unit Cell Model, is proposed for calculating of the effective thermal conductivity of polydispersed packed beds. In this new approach, the effect of packing density is incorporated by the use of (i) an initial porosity to take into account the packing of mono‐sized particles, and (ii) the packing size ratio as a measure of the particle‐particle interaction. The proposed approach was validated with the experimental measurements of binary and ternary beds. This new approach demonstrates that the effective thermal conductivity of beds composed of polydispersed particles can be simulated for any composition without the need to measure the in situ porosity.
Multicriteria Optimization of a High‐Yield Pulping Process
Authors: Thibault Jules , Lanouette Robert , Fonteix Christian , Kiss Laszlo N. 
Published: July 2010

AbstractThis work deals with the application of a multicriteria optimization technique for the optimization of a jack pine pulping process, which has a large number of input and output variables. The optimization process is mainly comprised of two steps: reduction of the volume of the search space and determination of good compromise solutions. In the first step, the Pareto domain is approximated by a large number of possible solutions. The optimization technique uses the concept of preference, indifference and veto to determine the best solutions. Results show that an optimal solution zone can be defined and zones of decreasing preference can be drawn.
Spout Shape Predictions in Spouted Beds
Authors: Zanoelo Éverton F. , Rocha Sandra C. S. 
Published: July 2010

AbstractA theoretical study to predict spout‐annulus interface variation with bed level for different column geometries of spouted beds is proposed. A previous mathematical model (Krzywanski et al., 1989), developed for spout shape predictions in two‐dimensional spouted beds, is here proposed to be applied also for cylindrical, conical or cone‐based cylindrical columns. Its predictions depend on the average spout diameter and on the spout expansion angle. While there exists empirical equations available to estimate the first model parameter, the second one requires a rigorous stress analysis of the particles at the entrance of the bed. To avoid this difficulty, this work proposes a simple mathematical strategy to calculate the spout expansion angle. The reliability of this approach was checked by comparison with several experimental results obtained in cone‐based cylindrical (Lim et al., 1974; Wu et al., 1987; He et al., 1998) and rectangular (Zanoelo, 1994) spouted beds.
Wall Effects for the Free Rise of Solid Spheres in Moderately Viscous Liquids
Authors: Dewsbury Kevin H. , Tzounakos Aristotelis , Karamanev Dimitre G. , Margaritis Argyrios 
Published: July 2010

AbstractFor the first time ever, the influence of wall effects on the free rise of a buoyant solid sphere in a square column in a non‐Newtonian (pseudoplastic) fluid was determined. It was found that in most cases, as the column width decreased, the terminal rise velocity of the sphere would decrease as well. It was also discovered that wall effects could change the rising sphere trajectory. Spheres that displayed a spiraling trajectory in larger columns would display a more linear trajectory in smaller columns. Occasionally, due to this change in trajectory, the solid sphere terminal velocity would increase as the column width decreased. This phenomenon (the positive wall effect) has not been reported for falling spheres in Newtonian or non‐Newtonian fluids.
Gas—Liquid Flow Through Helical Coils in Horizontal Orientation
Authors: Mandal Sailendra Nath , Das Sudip Kumar 
Published: July 2010

AbstractExperimental investigations have been carried out to evaluate the two‐phase pressure drop and the holdup for gas‐Newtonian liquid flow through helical coils. 24 helical coils and three different liquids were used for the experiments. Empirical correlations have been developed to predict the two‐phase friction factor and the liquid holdup as functions of various physical and dynamic variables of the system. Statistical analysis of the correlations suggests that they are of acceptable accuracy.
Drop Deformation and Breakup Mechanisms in Viscoelastic Model Fluid Systems and Polymer Blends
Authors: Mighri Frej , Huneault Michel A. 
Published: July 2010

AbstractThis paper reviews the dispersion mechanisms in viscoelastic systems under relatively high shear rate conditions. In particular, two non‐Newtonian deformation and breakup mechanisms were revealed by flow visualization in a transparent Couette shearing setup. The first one is the dispersed droplet elongation perpendicular to the flow direction. This was observed only for viscoelastic drops and had been associated to normal force buildup in the droplet. The second deformation/breakup mechanism was observed in very high viscosity ratio polymer systems. It consists in erosion at the drop surface. Clouds of very small ribbons and sheets were developed around the drop then stretched and finally broken into very small droplets, rapidly distributed in the matrix.
Online Light Scattering Measurements as a Means to Assess Influence of Extrusion Parameters on Non‐reactive Polymer Blend Morphology: Experimental Procedure and Preliminary Results
Authors: Serra Christophe , Schlatter Guy , Bouquey Michel , Muller René , Terrisse Jean 
Published: July 2010

AbstractThe influence of extrusion parameters on the morphology of non‐reactive blends has been investigated by means of online light‐scattering measurements. A light‐scattering device was especially designed to be mounted on a twin screw extruder at different locations along the barrel. The obtained light‐scattering patterns were interpreted with respect to the variation of the processing parameters. Preliminary results show that there is little effect of the rotational speed, position along the screw and feed throughput on the morphology but a quite noticeable effect of the blend composition. These results were confirmed by SEM micrographs.
Evolution of Chemistry, Morphology and Rheology of Various Polymer Systems along a Twin‐Screw Extruder
Authors: Covas José A. , Carneiro Olga S. , Maia João M. , Filipe Susana A. , Machado Ana V. 
Published: July 2010

AbstractIntermeshing twin‐screw extruders have been recently identified as useful in special application niches such as the extrusion of PVC dry blends (counter‐rotating machines) and compounding operations (co‐rotating machines). Thus, it is of interest to study the mechanical and/or chemical effects that occur along the screw axis of the extruders, since they will dictate the characteristics and performance of the final material. This work aims at illustrating the usefulness of a simple experimental tool recently developed for the study of the physical, chemical and morphological evolution along the extruder of polymer based systems, data being presented and discussed for a number of composites and blends.
Fiber Suspensions in Complex Geometries: Flow/Orientation Coupling
Authors: Verweyst Brent E. , Tucker Charles L. 
Published: July 2010

AbstractA Galerkin finite element solution is developed for the flow of fiber suspensions. Primary variables are velocity, pressure, and a second‐order tensor describing the fiber orientation. The model treats the orientation as three‐dimensional, includes fiber—fiber interaction effects, and uses an orthotropic closure approximation. The flow and orientation are strongly coupled through an orientation‐dependent constitutive equation. We explore the effect of this coupling on the fluid mechanics of fiber suspensions by studying three flows: an axisymmetric contraction, an axisymmetric expansion, and a center‐gated disk. Coupling enhances the corner vortex in the contraction, in quantitative agreement with published experiments and calculations. The expansion results demonstrate that the aligned‐fiber approximation is not valid for this flow. In the center‐gated disk the effects of coupling are modest and are only noticeable near the center of the disk. This supports the use of decoupled models for injection molding in thin cavities.
Numerical Analysis of the Coupling Between the Flow Kinematics and the Fiber Orientation in Eulerian Simulations of Dilute Short Fiber Suspensions Flows
Authors: Chinesta Francisco , Poitou Arnaud 
Published: July 2010

AbstractThis paper focuses on an accurate evaluation of short fibers suspensions models coupling the flow kinematics with the fiber orientation evolution. In coupled models the flow kinematics is usually solved using the finite element method, where the fiber orientation is introduced in the constitutive equation through its value in some points (nodes or integration points). In this paper we will compare in a simple steady shear flow, the exact solutions of the extra‐stresses associated with the fibers' presence with the numerical simulations obtained using both the method of characteristics and the discontinuous Galerkin's method to solve the equation governing the generalized gradient evolution, in order to avoid the introduction of any closure relation. The error introduced if a quadratic closure relation is considered in the constitutive equation will be also quantified.
Numerical Modelling of the Flow of Fibre Suspensions through a Planar Contraction
Authors: Azaiez Jalel , Guénette Robert 
Published: July 2010

AbstractThis study presents results of numerical simulations of the flow of fibre suspensions in a Newtonian fluid through a 4:1 planar contraction. Two approaches are adopted to determine the fibre orientation. The first one uses orientation tensors defined as dyadic products of the orientation vector, while the second one is based on the fibre aligned assumption. An implicit time discretization scheme and a mixed finite element method based on the introduction of the rate of deformation tensor as an additional unknown are used to obtain the steady‐state flow. The numerical technique we use allows us to examine the flow of fibre suspensions in both dilute and semi‐dilute regimes at high values of the parameters controlling inertial and fibre effects. The predicted flow patterns and fibre orientation are discussed, and a systematic comparison between the predictions of the two approaches is presented.
A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix
Authors: Lozano Tomas , Lafleur Pierre G. , Grmela Miroslav 
Published: July 2010

AbstractParticle size distribution affects strongly physical and mechanical properties of filled polymers. The proposed model uses agglomerate size population balance in its new mathematical formulation expressing agglomeration, break‐up and erosion as an evolution of one particle subjected to mean‐filed type interaction with others. The erosion parameters have been calculated with experiments in an internal mixer. Controlled breakup of agglomerates was carried out through capillary dies to evaluate breakup parameters. Calcium carbonate filled polypropylene system was used to validate the formulation.
Present Challenges in the Numerical Modeling of Polymer‐forming Processes
Authors: Vincent Michel , Vergnes Bruno , Demay Yves , Coupez Thierrey , Billon Noëlle , Agassant Jean‐François 
Published: July 2010

AbstractThe purpose of the present paper is to present an overview of the main progresses recently made in the numerical modeling of polymer‐forming processes and to describe the challenges to overcome in the near future. Examples are presented in different domains, such as die extrusion, injection molding, film processing, reactive extrusion and pipe reinforcement.
Paste Extrusion of Polytetrafluoroethylene (PTFE) Fine Powder Resins
Authors: Hatzikiriakos Savvas G. , Ariawan Alfonsius B. , Ebnesajjad Sina 
Published: July 2010

AbstractThe rheology of non‐melt processible polytetrafluoroethylene (PTFE) pastes has been studied using a capillary rheometer. It was found that fibrils of submicron dimensions are created during PTFE paste processing, which are responsible for the final strength of the extrudate. The mechanism of fibrillation is explained in terms of the unwinding of crystallites. To describe the effects of die design, a simple mathematical model has been developed. The model takes into account the elastic‐plastic (strain hardening) and viscous nature of the material in its non‐melt state. The model predictions are found to be consistent with experimental results obtained from macroscopic pressure drop measurements and flow visualization experiments.
Yield Stress Measurement of Silicon Nitride Suspensions
Authors: Zhu Lixuan , Papadopoulos Kyriakos , De Kee Daniel 
Published: July 2010

AbstractYield stress values of silicon nitride suspensions were measured via a novel slotted plate device and a constant stress rheometer and the results were compared. Test platform velocity, associated with the slotted plate method, was found to have a substantial effect on dynamic yield stress but not on static yield stress. The effects of suspension concentration and temperature on yield stress values were investigated. Yield stress measurements on mixtures of silicon nitride and alumina particles, as well as creep tests were performed.
Rheological Behavior of Coating Colors: Influence of Thickener
Authors: Moan Michel , Page Agnès , Carreau Pierre J. , Heuzey Marie‐Claude 
Published: July 2010

AbstractIn this work we have investigated the effect of rheology modifiers on the rheological properties of concentrated (65 solids mass%) kaolin suspensions and six different coating colors. Measurements have been performed on kaolin‐based suspensions, without rheology modifier and with either a classic cellulose thickener or associative polymers. It was noticed that suspensions containing a thickener had a much larger viscosity and storage and loss moduli than suspensions containing no rheology modifier. The enhancement of the rheological properties was found to be much more important for the suspensions containing the associative polymer. These observations have been related to steric stabilization of the suspensions, and to the occurrence of entanglements and bridging when the associative polymer was used as the thickener. The influence of the thickener on the rheological properties of the coating colors was found to be similar to that observed for the concentrated kaolin suspensions.
Orifice Flowmeter for Measuring Extensional Rheological Properties
Authors: Carreau Pierre J. , Ascanio Gabriel , Brito‐De La Fuente Edmundo , Tanguy Philippe A. 
Published: July 2010

AbstractExtensional rheological properties play an important role in processes in which the fluid is subjected to highly decelerated or accelerated flows. This paper describes an orifice flowmeter used to measure extensional properties of rheologically complex fluids at high strain rates. The operating principle of the flowmeter is based on the pressure drop due to the flow through a small size orifice. The flowmeter was first calibrated, by plotting the pressure drop‐flow rate curve of the orifice, in terms of a dimensionless Euler number versus Reynolds number. Newtonian fluids consisting of aqueous solutions of corn syrup were used as calibration fluids. The calibration curve was then used to determine the apparent extensional viscosity of three different paper coating colors. The apparent extensional viscosity is compared to the shear viscosity in terms of the Trouton ratio. The Trouton ratio for one coating color is shown to exceed considerably the theoretical value of 3 expected for Newtonian fluids.
Solid State Rheological Properties of Ultra‐High Molecular Weight Polyethylene Foams
Authors: Rodrigue Denis , Zhang Zhijie , Aït‐Kadi Abdellatif 
Published: July 2010

AbstractThe rheological properties of ultra‐high‐molecular‐weight polyethylene (UHMWPE) foams were studied using solid state rheometry. Frequency and temperature sweeps were performed in the linear viscoelastic regime. For comparison purposes, low‐density polyethylene (LDPE) and high density polyethylene (HDPE) foams were also studied. For the range of densities under consideration (200‐700 kg/m3), several models for prediction of elastic moduli were compared. It was found that none of the models succeeded in representing completely the mechanical behavior of foams. Further refinements must be made in order to take into account parameters relating the morphology of the foam to its mechanical properties.
How to Make Inherent Safety Practice a Reality
Authors: Khan Faisal I. , Amyotte Paul R. 
Published: July 2010

AbstractIn recent years there has been an increased effort to develop inherently safer chemical processes, focusing on changing the process to eliminate hazards, rather than accepting the hazards and developing add‐on features to control them. This paper discusses design approaches to inherently safer processing, including examples of inherent safety principles. The paper also presents a state‐of‐the‐art review of the initiatives taken by various groups and agencies worldwide to promote inherent safety, and the tools developed to measure inherent safety for chemical processes. The discussion concludes with thoughts on why inherent safety is not yet a routine practice for accomplishing risk reduction, and suggestions for ways to make it routine (with reference to a brief case study).
Studies on Liquid—Gas and Three‐Phase Fluidized Beds with Pulsating Air Flows
Authors: Baker Christopher G. J. , Al‐Rashidi Thari S. T. , Khan Abdul R. 
Published: July 2010

AbstractThe effects of air‐flow pulsation and water and air flowrates on the hydrodynamics of liquid—gas and three‐phase fluidized beds containing 3‐mm glass beads have been studied in a 90‐mm i.d. column. Under steady‐flow conditions, both types of bed contained a relatively large number of small bubbles. With a pulsing air flow, however, a smaller number of much larger bubbles or slugs were formed. This was attributed to different mechanisms of bubble formation at the distributor. Variations in phase holdup were explained in terms of the effects of the operating parameters on the bubble characteristics.
Numerical Investigation of Turbulent Flow around a Rotating Stepped Cylinder for Corrosion Study
Authors: Yang Kyung‐Soo , Hwang Jong‐Yeon , Bremhorst Klaus , Nesic Srdjan 
Published: July 2010

AbstractDirect numerical simulation has been carried out for turbulent flow set up by a rotating cylinder with two backward‐facing steps axisymmetrically mounted in the circumferential direction. This flow geometry creates a qualitatively similar flow pattern as observed near a sudden pipe expansion or a plane backward‐facing step, characterized by flow separation and reattachment. A region of intense turbulence intensity and high wall‐shear‐stress fluctuations is formed in the recirculating region downstream of the step, where high mass‐transfer capacity was also experimentally observed. Since corrosion is frequently mass‐transfer controlled, our findings put forward this apparatus as a useful tool for future corrosion research.
Oxidative Coupling of Methane in a Negative DC Corona Reactor at Low Temperature
Authors: Bagheri‐Tar Faezeh , Khodadadi Abbasali , Malekzadeh Azim , Mohajerzadeh S Shamsoddin 
Published: July 2010

AbstractOxidative coupling of methane (OCM) in the presence of DC corona is reported in a narrow glass tube reactor at atmospheric pressure and at temperatures below 200°C. The corona is created by applying 2200V between a tip and a plate electrode 1.5 mm apart. The C2 selectivity as well as the methane conversion are functions of methane‐to‐oxygen ratio, gas residence time, and electric current. At CH4/O2 ratio of 5 and the residence time of about 30 ms, a C2 yield of 23.1% has been achieved. The main products of this process are ethane, ethylene, acetylene as well as CO and CO2 with CO/CO2 ratios as high as 25. It is proposed that methane is activated by electrophilic oxygen species to form methyl radicals and C2 products are produced by a consecutive mechanism, whereas COx is formed during parallel reactions.