共查询到20条相似文献,搜索用时 15 毫秒
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Rapid progress in the development of additive manufacturing technologies is opening new opportunities to fabricate structures that control mass transport in three dimensions across a broad range of length scales. We describe a structure that can be fabricated by newly available commercial 3‐D printers. It contains an array of regular three‐dimensional flow paths that are in intimate contact with a solid phase, and thoroughly shuffle material among the paths. We implement a chemically reacting flow model to study its behavior as an exchange chromatography column, and compare it to an array of 1‐D flow paths that resemble more traditional honeycomb monoliths. A reaction front moves through the columns and then elutes. The front is sharper at all flow rates for the structure with three‐dimensional flow paths, and this structure is more robust to channel width defects than the 1‐D array. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1874–1884, 2018 相似文献
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We report an approach to fully visualize the flow of two immiscible fluids through a model three‐dimensional (3‐D) porous medium at pore‐scale resolution. Using confocal microscopy, we directly image the drainage of the medium by the nonwetting oil and subsequent imbibition by the wetting fluid. During imbibition, the wetting fluid pinches off threads of oil in the narrow crevices of the medium, forming disconnected oil ganglia. Some of these ganglia remain trapped within the medium. By resolving the full 3‐D structure of the trapped ganglia, we show that the typical ganglion size, as well as the total amount of residual oil, decreases as the capillary number Ca increases; this behavior reflects the competition between the viscous pressure in the wetting fluid and the capillary pressure required to force oil through the pores of the medium. This work thus shows how pore‐scale fluid dynamics influence the trapped fluid configurations in multiphase flow through 3‐D porous media. © 2013 American Institute of Chemical Engineers AIChE J, 59:1022‐1029, 2013 相似文献
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William B. Krantz Hanyong Lee Siladitya Ray Chaudhuri Sun‐Tak Hwang 《American Institute of Chemical Engineers》2012,58(3):678-689
Density change during mass or heat transfer can cause convection in the absence of buoyancy forces. Prior studies have shown that this convection can be significant in the determination of diffusion coefficients and in the casting of polymeric membranes. Including this effect is challenging even for advanced numerical codes. A general methodology for obtaining the mass‐average velocity for unsteady‐state, one‐dimensional, multicomponent mass and/or heat transfer circumvents the problem of numerically solving the coupled continuity equation. Scaling analysis permits assessing the importance of this convection for a generic equation‐of‐state. Numerical predictions for evaporation from a liquid layer for components having density ratios of 1:1 and 0.7:1 indicate that ignoring convection results in errors of 34% and 24% in the evaporation time and final thickness, respectively. This convection also influences the evaporation in the percutaneous application of cosmetics, medications, and insecticides, curing of paints, varnishes, and lacquers, and formation of thin films. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
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George W. Johnson Arnold F. Bertelsen Jan Nossen 《American Institute of Chemical Engineers》2009,55(11):2788-2795
A new two‐phase roll wave model is compared with data from high pressure two‐phase stratified pipe flow experiments. Results from 754 experiments, including mean wave speed, wave height, pressure gradient, holdup and wave length, are compared with theoretical results. The model was able to predict these physical quantities with good accuracy without introducing any new empirically determined quantities to the two‐fluid model equations. This was possible by finding the unique theoretical limit for nonlinear roll amplitude and applying a new approach for determining the friction factor at the gas‐liquid interface. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
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海底油气管道的冷却传热过程是结蜡、水合物等海洋石油工业流动保障问题的关键控制因素。采用电容探针与热电偶、热电阻等流动及温度测量手段对不同冷却条件下空气-油段塞流的流动参数和传热参数进行实验测量,分析了空气-油段塞流流动参数对传热特性的影响,并与空气-水对流换热进行对比。结果表明,空气-油段塞流对流传热系数主要受液相折算速度的影响,且冷却液温度越低,管底热流体黏度越大,导致热边界层越厚,传热系数降低;受黏性力及边界层影响,对流传热系数远小于空气-水;沿管壁周向,从管顶到管底的对流传热系数不断增大。提出了适用于冷却条件下的油气段塞流传热关联式和传热模型。 相似文献
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Magali Dupuy Arunvady Xayasenh Hervé Duval Emmanuel Waz 《American Institute of Chemical Engineers》2016,62(3):891-904
The deposition of non‐Brownian particles from turbulent liquid‐flow onto channel walls is numerically analyzed. The approach combines Lagrangian particle tracking with a kinematic model of the near‐wall shear layer. For nonbuoyant particles, direct interception is the main deposition mechanism and the deposition velocity scales as the particle diameter (in wall units) to the power of 1.7. When wall/particle hydrodynamic interactions are taken into account, the deposition velocity is significantly reduced and the correction factor scales as the cubic root of the wall roughness to particle diameter ratio. For buoyant particles, sedimentation is usually the predominant deposition mechanism and the hydrodynamic interactions significantly affect the deposition velocity when the drainage characteristic time driven by buoyancy is of the order of the particle residence time close to the wall. Last, a wall‐function for the suspended particles is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 62: 891–904, 2016 相似文献
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Akhil Rao Jennifer S. Curtis Bruno C. Hancock Carl Wassgren 《American Institute of Chemical Engineers》2012,58(5):1381-1396
A numerical study of a dilute turbulent gas‐particle flow with inelastic collisions and turbulence modulation in an Eulerian framework is described. A new interpretation is provided for the interaction/coupling terms, based on a fluctuating energy transfer mechanism. This interpretation provides for a new robust closure model for the interaction terms with the ability to predict the turbulence dampening as well as the turbulence enhancement phenomenon. Further, the model developed herein is investigated along with a variety of other published closure models used for the interaction/coupling terms, particle drag, and solid stress. The models are evaluated against several sets of benchmark experiments for fully‐developed, turbulent gas‐solid flow in a vertical pipe. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
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Experimental study on the reaction rate of a second‐order chemical reaction in a planar liquid jet 下载免费PDF全文
Yasuhiko Sakai Kouji Nagata Osamu Terashima 《American Institute of Chemical Engineers》2014,60(11):3969-3988
Instantaneous concentrations of reactive species are simultaneously measured in a planar liquid jet with a second‐order chemical reaction to investigate the statistical properties of the chemical reaction rate and the validity of models which have been proposed for concentration correlation. The jet flow contains the reactant A, and the ambient flow contains the reactant B. The results show that the concentration correlation of the reactants makes a negative contribution to the mean reaction rate, and this contribution is important in the downstream direction. The concentration correlation changes owing to the chemical reaction. The effects of the chemical reaction on the concentration correlation change with the flow location and the Damköhler number. The concentration correlation predicted by the Toor's model and the three‐environment model are compared with the experimental results. The results show that these models fail to accurately estimate the concentration correlation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3969–3988, 2014 相似文献
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Two‐layer coating occurs in many products. Ideally, the liquids are deposited onto the substrate simultaneously. In the case of two‐layer slot coating, the interlayer between the coating liquids is subjected to enormous shearing. This may lead to flow instabilities that ruin the product. It is important to map the regions of the parameter space at which the flow is unstable. Most of the stability analyses of two‐layer rectilinear flow consider the position of the interlayer as an independent parameter. Classical results cannot be applied directly in coating flows. We present a linear stability analysis of two‐layer rectilinear flow considering the flow rates as an independent parameter. The predicted neutral‐stability curves define the region of stable flow as a function of the operating parameters. The range of coating operating conditions is restricted further, when the condition for the desirable interlayer separation point location are considered together with the stability condition. © 2010 American Institute of Chemical Engineers AIChE J, 2010 相似文献
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LES–Lagrangian‐particles‐simulation of turbulent reactive flows at high Sc number using approximate deconvolution model 下载免费PDF全文
Large eddy simulation (LES) with the approximate deconvolution model is combined with Lagrangian particles simulation (LPS) for simulating turbulent reactive flows at high Schmidt numbers Sc. The LES is used to simulate velocity and nonreactive scalar while reactive scalars are simulated by the LPS using the mixing volume model for molecular diffusion. The LES–LPS is applied to turbulent scalar mixing layers with a second‐order isothermal irreversible reaction at Sc = 600. The mixing volume model is implemented with the IEM, Curl's, and modified Curl's mixing schemes. The mixing volume model provides a correct decay rate of nonreactive scalar variance at high Sc independently of the number of particles. The statistics in the LES–LPS with the IEM or modified Curl's mixing scheme agree well with the experiments for both moderately‐fast and rapid reactions. However, the LPS with the Curl's mixing scheme overpredicts the effects of the rapid reaction. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2912–2922, 2016 相似文献
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Erik Kaunisto Anders Rasmuson Johan Bergenholtz Johan Remmelgas Lennart Lindfors Staffan Folestad 《American Institute of Chemical Engineers》2014,60(5):1863-1869
A proper mechanistic understanding of the deaggregation process of small colloidal particle aggregates is of generic importance within many fields of science and engineering. The methodology for modeling colloidal deaggregation is currently limited to analytical solutions in the two‐particle case and time consuming numerical algorithms, such as Brownian Dynamics (BD) simulations, for many‐particle aggregates. To address this issue, a simplified alternative model that describes deaggregation of few‐particle aggregates is presented. The model includes end‐particle deaggregation and a particle reconfiguration mechanism, which are the two most important mechanisms for deaggregation. Comparison of the calculated first passage time distribution for various two‐, three‐, four‐, and five‐particle aggregates with the corresponding result using BD simulations confirms the validity of the model. It is concluded that the dominating mechanism behind deaggregation can be quantified using a deaggregation number, which reflects the time scale for reconfiguration relative to the time scale for end‐particle deaggregation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1863–1869, 2014 相似文献
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Mélanie Jimenez Nicolas Dietrich Arnaud Cockx and Gilles Hébrard 《American Institute of Chemical Engineers》2013,59(1):325-333
A new method for determining the molecular diffusivity of oxygen in liquids is described. The technique was applied through a flat air–liquid interface in a Hele‐Shaw cell (5 × 5 × 0.2 cm3) and was based on planar laser‐induced fluorescence (PLIF) with inhibition. A ruthenium complex (C72H48N8O6Ru) was used as the fluorescent dye sensitive to oxygen. A mathematical analysis was developed to determine the molecular diffusivity of oxygen simply by localizing the gas diffusion front. The specificity of this mathematical analysis is that it does not require the properties of the fluids (such as the saturation concentration) to be considered, which is especially relevant for complex media that are sometimes difficult to characterize properly. This technique was applied to three different fluids (viscosities ranging from 1 to 2.4 mPa·s) corresponding to binary diffusion coefficients ranging from 9.5 × 10?10 to 2 × 10?9 m2/s. Experimental data were found with an uncertainty of about 5% and were in good agreement with the literature. Particle image velocimetry and numerical simulations were also carried out to determine the optimal gas flow rate (0.01 L/s) to reach purely diffusive transfer, and the corresponding hydrodynamic profiles of the two phases. © 2012 American Institute of Chemical Engineers AIChE J, 59: 325–333, 2013 相似文献
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Maria N. Pantzali Jelena Z. Kovacevic Geraldine J. Heynderickx Guy B. Marin Vladimir N. Shtern 《American Institute of Chemical Engineers》2015,61(12):4114-4125
A unique normalized radial pressure profile characterizes the bed of a gas‐solid vortex reactor over a range of particle densities and sizes, solid capacities, and gas flow rates: 950–1240 kg/m3, 1–2 mm, 2 kg to maximum solids capacity, and 0.4–0.8 Nm3/s (corresponding to gas injection velocities of 55–110 m/s), respectively. The combined momentum conservation equations of both gas and solid phases predict this pressure profile when accounting for the corresponding measured particle velocities. The pressure profiles for a given type of particles and a given solids loading but for different gas injection velocities merge into a single curve when normalizing the pressures with the pressure value downstream of the bed. The normalized—with respect to the overall pressure drop—pressure profiles for different gas injection velocities in particle‐free flow merge in a unique profile. © 2015 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 61: 4114–4125, 2015 相似文献