Apparent viscosity measurements in a homogeneous gas-fluidized bed

The construction of a gas-fluidized bed of annular cross-section, contained between two vertical cylinders, the internal one of which can be made to rotate at selected speeds, is described. The system was used to determine the apparent viscosity of a fine powder fluidized homogeneously by ambient nitrogen over a range of expansion conditions. The results revealed pseudo-plastic-type behavior, the measured apparent viscosities decreasing markedly with increasing shear stress.     

Verification of Eulerian–Eulerian and Eulerian–Lagrangian simulations for turbulent fluid–particle flows

We present a verification study of three simulation techniques for fluid–particle flows, including an Euler–Lagrange approach (EL) inspired by Jackson's seminal work on fluidized particles, a quadrature–based moment method based on the anisotropic Gaussian closure (AG), and the traditional two‐fluid model. We perform simulations of two problems: particles in frozen homogeneous isotropic turbulence (HIT) and cluster‐induced turbulence (CIT). For verification, we evaluate various techniques for extracting statistics from EL and study the convergence properties of the three methods under grid refinement. The convergence is found to depend on the simulation method and on the problem, with CIT simulations posing fewer difficulties than HIT. Specifically, EL converges under refinement for both HIT and CIT, but statistics exhibit dependence on the postprocessing parameters. For CIT, AG produces similar results to EL. For HIT, converging both TFM and AG poses challenges. Overall, extracting converged, parameter‐independent Eulerian statistics remains a challenge for all methods. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5396–5412, 2017     

A new solution technique for fluid–solid reactions

Fluid–solid reactions are very important in the chemical and metallurgical process industries. Several models described these reactions such as volume reaction model, grain model, random pore model and nucleation model. These models give two nonlinear-coupled partial differential equations (CPDE). When the fluid concentration is high (for example in liquid–solid reactions), the fluid mass balance must be written as an unsteady equation. There is not any analytical or approximate solution for these equations, due to its complex CPDE. In this work, a new solution technique (quantized method) has been applied to these unsteady state CPDE. The results of this method (conversion–time profiles) have been compared with some existing numerical solutions with a good accuracy. Therefore, this method can be used for rapid estimation of kinetic parameters from experimental data.     

A new model for simulating particle transport in a low‐viscosity fluid for fluid‐driven fracturing

Fluid‐driven fracture (i.e., Hydraulic fracturing) is an important way to stimulate the well productivity in the development of unconventional reservoirs. A low‐viscosity fluid called slickwater is widely used in the unconventional fracturing. It is a big challenge to simulate the particle (or proppant) transport in the low‐viscosity fluid in a field‐scale fracture. A new model to simulate particle transport in the low‐viscosity fluid in a field‐scale fracture is developed. First, a new parameter is defined, called the rate of proppant bed wash‐out, by which we incorporated the mechanism of proppant bed wash‐out into Eulerian‐Eulerian proppant transport model. Second, we proposed a novel way to consider the effect of proppant settling on the proppant concentration in the upper layer (or suspending layer) to accurately simulate the proppant transport. Additionally, a dimension reduction strategy was used to make the model quickly solved. Our simulation results were compared with published experimental data and they were consistent. After validation, the effect of fluid viscosity, injection rate, fracture height, and proppant concentration on the proppant distribution in a fracture is investigated. This study provides a new model to simulate particle transport. Meanwhile, it gives critical insights into understanding particle transport in the field‐scale fracture. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3542–3552, 2018     

纳米流体黏度特性

引言纳米流体是将纳米粒子添加到基液中形成的稳定悬浮混合液。近10年来,国内外许多学者对纳米流体的导热性能进行了大量研究,添加纳米粒子后溶液的导热能力明显加强。Jung等[1]对微渠道中的纳米流体对流传热特性进行了研究,研究发现粒径为170nm、体积分数为1.8%的Al2O3-水纳     

稠油包水乳状液的表观黏度

以渤海SZ36-1稠油、矿化水为工质配制了2组不同液滴直径的W/O型乳状液,研究了温度、含水率、剪切率和液滴直径对乳状液黏度的影响。结果表明,温度对乳状液表观黏度的影响非常明显,而对相对黏度的影响却较小;同时含水率、剪切率和液滴直径也是影响乳状液黏度的重要因素,低含水率下,剪切率、液滴直径对黏度的影响不明显,而当含水率较高时,剪切率、液滴直径的影响非常突出,乳状液呈现出强烈的剪切稀释特性。利用国内外现有的一些黏度模型对实验获得的黏度数据进行了预测分析,发现Brinkman(1952)模型具有较好的预测精度。     

Apparent elongational viscosity of dilute polymer solutions

Apparent elongational viscosity studies were made on dilute solutions of high molecular weight polymers using a fiber spinning apparatus designed for low shear viscosity liquids with substantial elongational effects. The experimental method involved the flow of solutions of polyacrylamide and poly(ethylene oxide) from a tube into an evacuated vessel. Experimental results showed that the apparent elongational viscosity obtained from the jet shape increased linearly with the stretch rate.     

Pervaporation separation of a water–ethanol mixture by PSF–PEG membrane

For dehydrating a water–ethanol mixture by pervaporation, a polysulfone–And poly(ethylene glycol)(PSF–PEG) membrane was prepared. The separation performance of water and ethanol was found to strongly depend on the diffusion selectivity of permeates. On the other hand, the solubility selectivity of water to ethanol showed only minor change with an increasing PEG composition of the PSF–PEG membrane. This study found that the PEG content in a PSF–PEG membrane showed mobility enhancement of pervaporation properties and that the diffusion difference of permeates increased with increasing PEG content. The effect of PEG content on separation performance was a result of the improvement of the permeate diffusion properties of the PSF/PEG membrane. The diffusion difference in the membrane, not the solubility of water–ethanol in the membrane, was the dominant factor for the separation. Suitable PEG content in PSF/PEG membranes can prepare a high‐performance pervaporation membrane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2158–2164, 2003     

Dispersed oil–water–gas flow through a horizontal pipe

An experimental study of three‐phase dispersed flow in a horizontal pipe has been carried out. The pressure drop over the pipe strongly increases with increasing bubble and drop volume fraction. Because of the presence of drops the transition from dispersed bubble flow to elongated bubble flow occurs at a lower gas volume fraction. The gas bubbles have no significant influence on the phase inversion process. However, phase inversion has a strong effect on the gas bubbles. Just before inversion large bubbles are present and the flow pattern is elongated bubble flow. During the inversion process the bubbles break‐up quickly and as the dispersed drop volume fraction after inversion is much lower than before inversion, a dispersed bubble flow is present after inversion. (When inversion is postponed to high dispersed phase fractions, the volume fraction of the dispersed phase can be as high as 0.9 before inversion and as low as 0.1 after inversion.) © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Correlating viscosity in urea–formaldehyde polymerization

The objective of this study was to find a correlation for the viscosity changes during step polymerization of urea and formaldehyde. For this reason, a kinetic model for the condensation reactions was proposed, and using this model, a correlation for the kinematic viscosity changes of the solution during polymerization was obtained. Viscosity measurements of the samples during condensation reactions were carried out using Ubbelohde viscometers at intervals. The experimental data were curve fitted using our model, which was found to correspond very well. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 631–636, 1998     

纤维素/[BMIM]Cl体系表观黏度影响因素

以1-丁基3-甲基咪唑氯盐([BMIM]Cl)离子液体为溶剂,研究了高聚合度的针叶木浆(DP=1460)在[BMIM]Cl溶剂体系中的活化能,考察了溶解温度、浆粕浓度和介孔硅添加量对纤维素/[BMIM]Cl体系表观黏度的影响.研究表明:纤维素/[BMIM]Cl体系黏流活化能AE=50.8 kJ/mol,针叶浆粕含量对体...     

Apparent viscosity reduction during microwave sintering of amorphous silica

The sintering of arrays of spherical particles of amorphous SiO₂ was investigated experimentally under microwave (24 GHz) and conventional heating. The materials under study were compacts formed by gravitational sedimentation of monodisperse silica microspheres (1 µm in diameter). The kinetics of neck growth between individual particles was investigated by analyzing SEM images. It was found that the rates of viscous mass transport under microwave heating were significantly higher than those under conventional heating. The values of the viscosity obtained under microwave heating were significantly (by more than an order of magnitude) lower compared to conventional heating. Possible reasons for the viscosity decrease observed under microwave heating may be associated with the influence of water vapor and the action of the electromagnetic field on impurity ions. The interrelation of the observed effect with flash sintering and microwave-enhanced mass transport is discussed.     

Effects of fluid–fluid interfacial elasticity on droplet formation in microfluidic devices

Biomolecules adsorb at fluid–fluid interfaces and can form a cohesive interfacial network imparting distinctive local interfacial mechanics. This modification of interfacial behavior is empirically known to significantly affect the stability and flow behavior of foams and emulsions. Droplet formation in the presence of interfacial networks is investigated in a flow‐focusing microfluidic device using designed peptide surfactants, which allow decoupled control of interfacial rheology and interfacial tension. The influence of interfacial elasticity on droplet breakup, satellite droplet formation and droplet size are reported. The presence of high interfacial elasticity strongly affects the mechanism of droplet breakup by delaying neck thinning and altering interfacial shape at the point of droplet detachment, resulting in the suppression of satellite droplet formation and a decrease in droplet size. We report a correlation between dimensionless droplet size and a new dimensionless grouping which combines flow‐rate ratio with the ratio of interfacial tension and interfacial elasticity. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Melt viscosity characteristics of methacrylate–styrene copolymers

The activation energies of flow E_A of methacrylate–styrene copolymers containing n-butyl, n-hexyl, n-heptyl, n-octyl, n-decyl, n-dodecyl, n-tridecyl, n-octadecyl, and cyclohexyl methacrylate have been investigated as a function of molecular weight, composition, and methacrylate monomer. Below a critical pendent group molar volume per chain unit (120 ± 10 ml Le Bas units), E_A was found to increase with molar volume; and above this value, a decrease in E_A was observed, reflecting a decrease in copolymer density. Copolymers with pendent group molar volumes per average chain unit of between 96 and 140 ml (Le Bas units) were found to exhibit sufficiently high E_A values to render them suitable for use in thermoplastic and photothermoplastic devices with superior development and erasure rates, at temperatures which enabled the attainment of the development and erasure viscosities with a low expenditure of heat energy. Methacrylate–styrene copolymers with long-chain ester methacrylates (viz., n-decyl and n-dodecyl methacrylate) were found to exhibit critical molecular weights M_c below 3000; and M_c was found to decrease with increasing methacrylate tail length and methacrylate concentration. These M_c values correspond to critical chain lengths Z_c below 45. Similar Z_c values have been previously reported for acrylonitrile–methyl methacrylate copolymers³⁰ and ethylene–propylene copolymers.²⁸     

Moulding properties of a Nigerian silica–clay mixture for foundry use

The moulding properties of Igbokoda silica sand, bonded with Ijero–Ekiti clay, were investigated. American Foundrymen Society (AFS) standard cylindrical samples dimensioning Ø50 mm × 50 mm in height were prepared from various sand–clay ratios with 5% tempering water, by applying three ramming blows of 6.666 g each from a height of 50 mm as required for foundry sands. The samples were subjected to various physical and mechanical tests. These include permeability, green compression strength, and dry compression strength tests. Green shear strength, dry shear strength, field mould strength, shattered index and refractoriness tests were also carried out on the samples. Samples containing 23–32% clay were found to possess adequate permeability, good strength and refractoriness suitable for casting of both ferrous and non-ferrous alloys.     

Design of gas‐phase synthesis of core‐shell particles by computational fluid–aerosol dynamics

Core‐shell particles preserve the bulk properties (e.g., magnetic and optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO₂ nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core‐shell nanoparticles. The predicted extent of hermetic coating shells is compared with the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO₂ shells prevent the photocatalytic activity of titania. Finally, the performance of a simpler, plug‐flow coating model is assessed by comparisons with the present detailed computational fluid dynamics (CFD) model in terms of coating efficiency and silica average shell thickness and texture. © 2011 American Institute of Chemical Engineers AIChE J, 2011