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 ...
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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.
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 i...
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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.
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 a...
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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.
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 ...
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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.
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 ve...
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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...
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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 experimenta...
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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.
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-ca...
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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%.
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...
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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.
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...
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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.
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