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Inside Front Cover: One‐Pot Synthesis and Hierarchical Assembly of Hollow Cu2O Microspheres with Nanocrystals‐Composed Porous Multishell and Their Gas‐Sensing Properties (Adv. Funct. Mater. 15/2007)

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Advanced Functional Materials 2007年第15期17卷

作者： H. Zhang Q. Zhu Y. Zhang Y. Wang L. Zhao B. Yu Multiphase Reaction Laboratory Institute of Process Engineering Chinese Academy of Sciences P.O. Box 353 Beijing 100080 (P.R. China) State Key Laboratory of Transducer Technology Institute of Electronics Chinese Academy of Sciences Beijing 100080 (P.R. China)

On p. 2766, Qinshan Zhu and co‐workers report on multishell hollow Cu 2 O microspheres that are synthesized by a facile and one‐pot solvothermal route. A two‐step organization process, in which hollow microspheres of Cu 2 (OH) 3 NO 3 are formed first followed by reduction to Cu 2 O by glutamic acid, leads to the special multishell and hollow microstructures. Interestingly, a Cu 2 O gas sensor fabricated with the multishell microspheres shows a much higher sensitivity to ethanol than solid Cu 2 O microspheres. Hierarchical assembly of hollow microstructures is of great scientific and practical value and remains a great challenge. This paper presents a facile and one‐pot synthesis of Cu 2 O microspheres with multilayered and porous shells, which were organized by nanocrystals. The time‐dependent experiments revealed a two‐step organization process, in which hollow microspheres of Cu 2 (OH) 3 NO 3 were formed first due to the Ostwald ripening and then reduced by glutamic acid, the resultant Cu 2 O nanocrystals were deposited on the hollow intermediate microspheres and organized into finally multishell structures. The special microstructures actually recorded the evolution process of materials morphologies and microstructures in space and time scales, implying an intermediate‐templating route, which is important for understanding and fabricating complex architectures. The Cu 2 O microspheres obtained were used to fabricate a gas sensor, which showed much higher sensitivity than solid Cu 2 O microspheres.

关键词： Hollow materials Microspheres Nanocrystals Sensors, gas

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Convenient model of pressure gradient calculation of gas-liquid slug flow in vertical wellbore

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Zhongguo Shiyou Daxue Xuebao (Ziran Kexue Ban)/Journal of China University of Petroleum (Edition of Natural Science) 2006年第4期30卷 75-77+85页

作者： Wang, Wei-Yang Chen, Ting-Kuan Luo, Yu-Shan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China College of Petroleum Engineering China University of Petroleum Dongying 257061 China

Based on mechanistic analysis of gas-liquid slug flow in vertical wellbore, a convenient model for pressure gradient calculation was developed by equivalent unit cell approach. The method of predicting liquid holdup in liquid slug was determined according to experimental data, and correlation experimental data from literatures were used to evaluate the model. The analysis results show that this model is relative to few parameters and easy to calculate, and the test data from different sources can be predicted with fairly well precision. In addition, much difference results can be achieved by variant correlations for liquid holdup in liquid slug, but the prediction of pressure gradient is not sensitive to the liquid holdup under the experimental conditions.

关键词： Gas-liquid slug flow multiphase flow Pressure gradient Vertical wellbore

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Two dimensional numerical simulation of tapered pulse tube refrigerator

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第2期27卷 199-201页

作者： Zhao, Chun-Feng He, Ya-Ling Ding, Wen-Jing Yang, Wei-Wei Tao, Wen-Quan State Key Lab. of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Two-dimensional numerical simulation of the viscous compressible oscillating flow was carried out for the uniform cross-section and tapered pulse tubes by using a compressible SIMPLEC algorithm code developed by the authors. Effects of the taper angle on the performance of the pulse tube refrigeration were studied. The results showed that there was an optimum taper angle for tapered pulse tube refrigerator. With this optimum taper angle, the refrigerator performance can be improved a lot. But when the taper angle becomes larger than the optimum value, the cooling performance becomes inferior to that of the circular tube. The inherent mechanism of how the tapered pulse tube affects the performance of pulse tube refrigerator was also studied from the view point of second flow distribution in the pulse tube. Compared to the uniform cross-section pulse tube, the values of second flow in tapered pulse tube change a lot and the distribution of second flow becomes uneven as well. This is the main reason that the performance of tapered pulse tube can be improved compared to uniform cross-section pulse tube.

关键词：锥形脉管二次流数值研究

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HYDRODYNAMIC RESISTANCE EFFECT OF FLUID LAYER BETWEEN TWO IMMERSED APPROACHING PARTICLES

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China Particuology 2006年第5期4卷 220-228页

作者： Yanpeng Li Bofeng Bai School of Environmental Science and Engineering Chang'An University Xi'an 710064 P.R. China State Key Lab of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 P.R. China

A three-dimensional direct simulation of an immersed solid particle approaching another particle, or a flat wall, is conducted to investigate the mechanics of hydrodynamic impact of immersed particles. The simulation method is based on a modified immersed boundary method using a fixed grid system. When the particle separation distance becomes smaller than grid spacing, to account for the hydrodynamic resistance effect of liquid layer between particles near contact, a microlayer model is developed to allow determination of the pressure profile within the micro-layer without neglecting the inertial force of the layer flow. The pressure force is then taken into account in equation of particle motion. Comparisons of the simulation results with the experimental results reported in the literature are shown to substantiate the model presented in this study. The simulations reveal the complex three-dimensional flow field of the liquid and the motion of the approaching particle. The fluid pressure in the gap caused by the unsteady motion of the particle is significantly increased when the separation distance of particles is less than about one-tenth diameters of particle. Therefore the velocity of approaching particle starts to decrease due to the hydrodynamic resistance force at this position.

关键词： direct simulation microlayer model immersed boundary method hydrodynamic resistance effect

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Swirling flow of a viscoelastic fluid with free surface - Part II: Numerical analysis with extended marker-and-cell method

Swirling flow of a viscoelastic fluid with free surface - Pa...

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作者： Yu, Bo Wei, Jinjia Kawaguchi, Yasuo Department of Oil and Gas Storage and Transportation Engineering China University of Petroleum Beijing 102249 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering Faculty of Science and Technology Tokyo University of Science Noda Chiba 278-8510 Japan

In Part I [Wei et al., 2004, 2004 ASME Int. Mech. Eng. Conference], we presented the experimental results for swirling flows of water and cetyltrimethyl ammonium chloride (CTAC) surfactant solution in a cylindrical vessel with a rotating disk located at the bottom for a Reynolds number of around 4.3 × 104 based on the viscosity of solvent. For the large Reynolds number, violent irregular instantaneous secondary flows at the meridional plane were observed by use of a particle image velocimetry system. Because of the limitations of our computer resources, we did not carry out direct numerical simulation for such a large Reynolds number. The LES and turbulence model are alternative methods, but a viscoelastic LES/turbulence model has not yet been developed for the surfactant solution. In this study, therefore, we limited our simulations to a laminar flow. The marker-and-cell method proposed for Newtonian flow was extended to the viscoelastic flow to track the free surface, and the effects of Weissenberg number and Froude number on the flow pattern and surface shape were studied. Although the Reynolds number is much smaller than that of the experiment, the major experimental observations, such as the inhibition of primary and secondary flows and the decrease of the dip of the free surface by the elasticity of the solution, were qualitatively reproduced in the numerical simulations. Copyright © 2006 by ASME.

关键词： Fluids

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Swirling flow of a viscoelastic fluid with free surface - Part I: Experimental analysis of vortex motion by PIV

Swirling flow of a viscoelastic fluid with free surface - Pa...

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作者： Wei, Jinjia Li, Fengchen Yu, Bo Kawaguchi, Yasuo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China University of Tokyo Meguro-ku Tokyo 153-5805 Japan Oil and Gas Storage and Transportation Engineering China University of Petroleum Beijing 102249 China Department of Mechanical Engineering Faculty of Science and Technology Tokyo University of Science Noda 278-8510 Japan

The swirling flows of water and CTAC (cetyltrimethyl ammonium chloride) surfactant solutions (50-1000 ppm) in an open cylindrical container with a rotating disc at the bottom were experimentally investigated by use of a double-pulsed PIV (particle image velocimetry) system. The flow pattern in the meridional plane for water at the present high Reynolds number of 4.3 × 104 differed greatly from that at low Reynolds numbers, and an inertia-driven vortex was pushed to the comer between the free surface and the cylindrical wall by a counter-rotating vortex caused by vortex breakdown. For the 1000 ppm surfactant solution flow, the inertia-driven vortex located at the corner between the bottom and the cylindrical wall whereas an elasticity-driven reverse vortex governed the majority of the flow field. The rotation of the fluid caused a deformation of the free surface with a dip at the center. The dip was largest for the water case and decreased with increasing surfactant concentration. The value of the dip was related to determining the solution viscoelasticity for the onset of drag reduction. Copyright © 2006 by ASME.

关键词： Fluids

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Liquid kinematic viscosity of the binary mixtures of methanol and castor oil

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第SUPPL. 1期27卷 79-81页

作者： Meng, Xian-Yang Wu, Jiang-Tao Liu, Zhi-Gang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The liquid kinematic viscosity of the binary mixtures of methanol and castor oil are reported over the temperature range from 243~353 K made with a calibrated Ubbelohde-type capillary viscometer. The total experimental uncertainty is less than 1.06%. In addition, the results were correlated as a function of temperature as the kinematic viscosity equation of the binary mixtures. The absolute average deviation and the maximum deviation of the experimental results from the correlated equation are 1.11% and 3.31%, respectively.

关键词： Castor oil Kinematic viscosity Liquid mixtures Methanol

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New method of preparing solid solution ZnS-CuInS2 and its activity of photocatalytic splitting water for hydrogen production

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology 2006年第SUPPL. 2期28卷 240-244页

作者： Guo, Peng-Hui Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Synthesis of solid solution ZnS-CuInS2 has been demonstrated. The crystallinity and stability of catalysts were highly improved by the combination of two usual ways used for improving the crystallinity of materials-calcination at high temperature or hydrothermal, so was the activity of photocatalytic splitting water for hydrogen production. The catalysts were characterized by XRD, BET, SEM, XRF and UV-Vis. The results of the photocatalytic hydrogen production showed that the catalyst had the highest stability and activity by H2S inflowing to the metal cation solution following with calcination and hydrothermal. After the catalyst was loaded with 3% Pt, the velocity of hydrogen production has been further improved to 127 μmol/h. And its apparent quantum efficiency at 420 nm was up to 4.43%.

关键词： Photocatalytic hydrogen production Preparation ZnS-CuInS2 solid solution

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Shape of isolated bubble in intermittent flows in horizontal straight tube

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第3期27卷 433-436页

作者： Gu, Han-Yang Guo, Lie-Jin Zhang, Xi-Min Wang, Zhi-Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

An experimental study of the shape of a single bubble similar to those observed in horizontal plug/slug flow was performed by visual observation and conductance probes in this paper. The results show that the shape of the nose and body of bubble depends on the Froude number defined by gas/liquid mixture velocity, whereas the shape of the back region of bubble depends on both the Froude number and bubble length. The photographic pictures show that the motion of bubble is related to the characteristics of bubble head and the transition from plug flow to slug flow occurs when the back of the bubble changes from staircase to hydraulic jump pattern with increasing the Froude number and bubble length.

关键词： Bubble shape flow pattern transition Plug flow Slug flow

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Numerical study of heat transfer and fluid flow in a periodically wavy channel

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Jisuan Wuli/Chinese Journal of Computational Physics 2006年第1期23卷 93-97页

作者： Xie, Gong-Nan Wang, Qiu-Wang Luo, Lai-Qin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The periodically fully developed laminar heat transfer and fluid flow in a two-dimensional wavy channel in a compact heat exchanger are investigated numerically. Calculations are performed at Pr = 0.7, in the range of Re = 100-1100 with non-orthogonal non-staggered grids. The Semi-Implicit Method for Pressure Linked Equations Revised (SIMPLER) algorithm in the curvilinear body-fitted coordinates is used. The effect of the wavy height and distance on momentum and heat transfer is studied. Performance of model parameters is evaluated. It is shown that the overall Nusselt numbers and friction factors increase with the increase of Reynolds numbers. The friction factors and overall Nusselt numbers increase as increasing the wavy height or decreasing the wavy distance. The overall Nusselt numbers increase significantly with the wavy height, especially at high Reynolds numbers. The best wavy height and distance are 1.15 mm and 13 mm, respectively.

关键词： Channel flow

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