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On the viscosity of magnetic fluid with low and moderate solid fraction

Particuology 2008年第3期6卷 191-198页

作者： Zhiqiang Ren Yanping Han Ruoyu Hong Jianmin Ding Hongzhong Li Department of Chemical Engineering and Key Laboratory of Organic Synthesis of Jiangsu Province Soochow University SIP Suzhou 215123 China State Key Laboratory of Multiphase Reaction Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China IBM HYDA/050-3 C202 3605 Highway 52 North Rochester MN 55901 USA

The design of a pressurized capillary rheometer operating at prescribed temperature is described to measure the viscosity of magnetic fluids （MFs） containing Fe3O4 magnetic nanoparticles （MNPs）. The equipment constant of the rheometer was obtained using liquids with predetermined viscosities. Experimentally measured viscosities were used to evaluate different equations for suspension viscosities. Deviation of measured suspension viscosities from the Einstein equation was found to be basically due to the influence of spatial distribution and aggregation of Fe3O4 MNPs. By taking account of the coating layer on MNPs and the aggregation of MNPs in MFs, a modified Einstein equation was proposed to fit the experimental data. Moreover, the influence of external magnetic field on viscosity was also taken into account. Viscosities thus predicted are in good agreement with experimental data. Temperature effect on suspension viscosity was shown experimentally to be due to the shear-thinning behavior of the MFs.

关键词： Rheology Capillary rheometer Magnetic fluid Viscosity Peclet number

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An Efficient Segregated Algorithm for Incompressible Fluid flow and Heat Transfer Problems - IDEAL (Inner Doubly Iterative Efficient Algorithm for Linked Equations) Part II: Application Examples

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Numerical Heat Transfer: Part B -- Fundamentals 2008年第1期53卷 18-38页

作者： Sun, D. L. Qu, Z. G. He, Y. L. Tao, W. Q. wqtao@*** State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi''an Jiaotong University Xi''an Shaanxi People''s Republic of China

In this article, comprehensive comparisons are made between the SIMPLER and IDEAL algorithms for four application examples. It is found that the IDEAL algorithm is efficient and stable not only for the simple, low-Re/Ra or coarse-mesh flow cases, but also for the complex, high-Re/Ra or fine-mesh flow cases. For the low-Re/Ra, coarse-mesh flow cases, the ratio of CPU time of IDEAL to that of SIMPLER ranges from 0.029 to 0.7. For the high-Re/Ra, fine-mesh flow cases, the IDEAL algorithm can obtain convergent results but the SIMPLER algorithm cannot, even though the underrelaxation factors are adjusted. [ABSTRACT FROM AUTHOR]

关键词： ALGORITHMS HEAT transfer FLUID mechanics FLUID dynamics HYDRODYNAMICS

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Theoretical model for interfacial structure in bubble slug

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Shanghai Jiaotong Daxue Xuebao/Journal of Shanghai Jiaotong University 2008年第6期42卷 1009-1012+1016页

作者： Gu, Han-Yang Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Nuclear Science and Engineering Shanghai Jiaotong University Shanghai 200240 China

Slug flow is a highly intermittent flow regime in which large bubble slugs flow alternately with liquid slugs at randomly fluctuating frequency. A one-dimensional model for the interfacial structure in bubble slug was developed based on mass and momentum conservation for bubble nose, body and tail as well as for a hydraulic jump at the rear of the bubble. The model can reproduce experimental results accurately. The results indicate that the interfacial structure is strongly dependent on the Froude number defined by gas/liquid mixture velocity, pipe inclination, and bubble length.

关键词： Gas-liquid flow Interfacial structure One-dimensional model

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Analysis of impedance with different discharge current in proton exchange membrane fuel cell

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2008年第5期42卷 622-625页

作者： Shang, Dehua Ma, Bin Zhang, Guangsheng Guo, Liejin Liu, Hongtan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering University of Miami Coral Gables FL 33124 United States

Considering the fact that proton exchange membrane (PEM) fuel cell has different impedance performances under different discharge currents, a PEM fuel cell with single serpentine flow field was investigated with electrochemical impedance spectroscopy, and the R (QR) equivalent circuit was used to calculate the circuit element parameters. The experimental results show that water in the fuel cell increases from insufficient to sufficient and then excessive with the increasing discharge current. Accordingly, the electrochemical reaction rate on the electrodes increases first and then decreases, thus the charge transfer resistance decreases and then increases. The impedance of PEM fuel cell increases obviously for high discharge currents due to the accessional impedance produced by double-layer effect, while the impedance reaches minimum at medium discharge current (5 A).

关键词： Proton exchange membrane fuel cells (PEMFC)

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Molecular dynamics simulation of a single polymer in hydrophilic nano-slits

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Chinese Science Bulletin 2008年第17期53卷 2599-2606页

作者： REN Ying GAO Jian GE Wei LI JingHai HU GuoHua State Key Laboratory of Multiphase Complex System Institute of Process Engineering Chinese Academy of Sciences Beijing 100090 China Graduate University of the Chinese Academy of Sciences Beijing 100039 China Laboratory of Chemical Engineering Sciences CNRS-ENSIC-INPL 1 rue Grandville BP 20451 Nancy 54001 France

The behavior of a single polyethylene polymer in aqueous solution confined between two hydrophilic walls is studied with molecular dynamics (MD) simulations. The thickness of the nano-slit ranges from 1.26 to 3.15 nm, which is comparative to the polymer dimension. A monotonic transition from 3D- to 2D-like configurations is observed as the distance between the two walls narrows. Monomers are compressed into several layers and the preferred bond orientations alternate between parallel and normal to the walls accordingly. The diffusivity in the direction parallel to the wall is always larger than the one perpendicular to it. Calculation of the entropy and enthalpy changes during the folding of the polymer chain alone cannot explain the spontaneous process. The corresponding increase in water entropy due to volume expansion may be large enough to result in the overall free energy decrease.

关键词：聚乙烯聚合体分子动力学模拟亲水性纳米裂缝

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Synthesis of Biodiesel from Soybean Oil and Methanol Catalyzed by Cationic Ion-exchange Resin in an Ultrasonic Reactor

Synthesis of Biodiesel from Soybean Oil and Methanol Catalyz...

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The 12th Asian Pacific Confederation of Chemical engineering Congress

作者： B.Yang Bolun Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University Xi'an Shaanxi 710049China

Biodiesel is generally produced by the transesterification of vegetable oils or animal fats com- posed of C-C fatty acid triglycerides with methanol under the presence of a catalyst. The conventional biodiesel product... 详细信息

关键词： pharmaceutical synthesis green chemistry green engineering solvent selection

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A parametric study to design an effective spray cooling deployment in an entrained-flow coal gasifier

A parametric study to design an effective spray cooling depl...

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25th Annual International Pittsburgh Coal Conference, PCC

作者： Wang, Qiu Liu, Peiyao Xu, Shisen Wang, Baomin Wang, Ting State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China Thermal Power Research Institute Xi'an Shaanxi China Energy Conversion and Conservation Center University of New Orleans New Orleans LA 70148 United States

ISBN: (纸本)189097725X

Gasification is a clean technique that converts coal into syngas, which can be cleaned much more easily than the coal itself. The raw sysgas exiting the gasifier is usually at a very high temperature. To protect the rearward equipment, the raw syngas needs to be cooled to allow appropriate cleaning of particulates, ashes, and sulfur before it exits the gasifier. Cooling of the syngas can be performed by employing heat exchangers or direct spray cooling. This paper focuses on conducting a 3-D CFD parametric study to aid in the design of an effective water spray cooling deployment. The studied parameters include water droplet sizes (100400m) and water injection angles. The goal is to cool the syngas from 1550C to 800C using the shortest spray section. The gasifier is designed to produce methanol at a full load condition, so the amount of sprayed water is fixed to ensure the syngas composition meets the specifications for methanol production. The gasifier is steam-oxygen blown with dry coal feed using approximately 960 tons per day. The results reveal that smaller droplets are effective in reducing the cooling section length. Moreover, using three water injection angles show that inclining the spraying angle upward 45 degrees could shorten the effective cooling length. This study provides a guide for cutting the cost of manufacturing a gasifier cooling section.

关键词： Coal

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Eulerian-eulerian simulation of CFB risers using an emms-based sub-grid scale model with an implicit cluster diameter correlation

Eulerian-eulerian simulation of CFB risers using an emms-bas...

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9th International Conference on Circulating Fluidized Beds, CFB 2008, in Conjunction with the 4th International VGB Workshop on Operating Experience with Fluidized Bed Firing Systems

作者： Wang, Junwu Cheng, Changjian Ge, Wei State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Science P.O. Box 353 Beijing 100080 China

ISBN: (纸本)9783930400577

The Energy-Minimization Multi-Scale (EMMS) model (Li et al., 1988;Li & Kwauk, 1994) is employed in Eulerian-Eulerian simulations of the hydrodynamics of a pilot scale CFB riser, with an implicit cluster diameter correlation accounting for the effect of sub-grid scale heterogeneity on inter-phase drag force. The simulated solid circulation flux, radial and axial solid concentration distributions and the radial particle velocity profile agree well with corresponding measurements. It presents a further step in establishing sub-grid scale models, which has been a focus in the study of gas-solid flows, on the basis of variational principles.

关键词： Drag

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Meso-scale structure - A challenge of computational fluid dynamics for circulating fluidized bed risers

Meso-scale structure - A challenge of computational fluid dy...

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9th International Conference on Circulating Fluidized Beds, CFB 2008, in Conjunction with the 4th International VGB Workshop on Operating Experience with Fluidized Bed Firing Systems

作者： Ge, Wei Wang, Wei Dong, Weigang Wang, Junwu Lu, Bona Xiong, Qingang Li, Jinghai State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P.O. Box 353 Beijing 100080 China

ISBN: (纸本)9783930400577

Multi-scale heterogeneous structures are characteristic of the concurrent-up gas-solid flow in circulating fluidized bed (CFB) risers, which stand for a grand challenge to accurate simulation of industrial-scale CFB risers with reasonable computational cost. Coarse-grid simulations using traditional two-fluid models (TFM), although efficient, are not accurate enough for the purpose of design and control of industrial units, while direct numerical simulations (DNS) starting from below the Kolmogorov scale and particle scale are currently unrealistic for this purpose. Coarse-grid simulations with proper sub-grid scale (SGS) models are expected to provide both reasonable accuracy and efficiency, but the closure of SGS models has been a long-lasting controversial issue. In this presentation, we review our attempts in providing such a closure with specific stability condition for flows in CFB risers on the grid scale, that is, the so-called analytical multi-scale approach and its later improvements and extensions. The resultant SGS model has been incorporated into commercial software and applied in the simulation of industrial CFB risers with various sizes and bed materials. Further extension of the model to mass transfer processes shows that superficial Reynolds number is insufficient for correlating mass transfer rate as multi-scale heterogeneity is not reflected in this criterion. The presentation will be concluded by prospects in multi-scale computational fluid dynamics of multiphase systems.

关键词： Computational fluid dynamics

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Efficient gasification of wet biomass residue to produce middle caloric gas

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Particuology 2008年第5期6卷 376-382页

作者： Guangwen Xu Takahiro Murakami Toshiyuki Suda Hidehisa Tani Yutaka Mito Research Laboratory IHI Co. Ltd. (IHI) Isogo-Ku Yokohama 235-8501 Japan State Key Laboratory of Multiphase Phase Complex System Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China Energy Research Division Kobe steel Co. Ltd. Kobe Hyogo 651-2271 Japan

Various process residues represent a kind of biomass resource already concentrated but containing water as much as 60 wt.%. These materials are generally treated as waste or simply combusted directly to generate heat. Recently, we attempted to convert them into middle caloric gas to substitute for natural gas, as a chemical or a high-rank gaseous fuel for advanced combustion utilities. Such conversion is implemented through dual fluidized bed gasification （DFBG）. Concerning the high water content of the fuels, DFBG was suggested to accomplish either with high-efficiency fuel drying in advance or direct decoupling of fuel drying/pyrolysis from char gasification and tar/hydrocarbon reforming. Along with fuel drying, calcium-based catalyst can be impregnated into the fuel, without much additional cost, to increase the fuel＇s gasification reactivity and to reduce tar formation. This article reports the Ca impregnation method and its resulting effects on gasification reactivity and tar suppression ability. Meanwhile, the principle of directly gasifying wet fuel with decoupled dual fluidized bed gasification （D-DFBG） is also highlighted.

关键词： High-water content biomass Catalytic gasification Dual fluidized bed gasification Decoupled gasification Calcium

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