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Structural and photoelectrochemical characterization of CdS thin film electrodes in photoelectrochemical water splitting system

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology 2006年第SUPPL. 2期28卷 568-573页

作者： Su, Jin-Zhan Li, Ming-Tao Zhang, Xi-Min Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The structural properties of CdS thin films obtained by ultrasonic spray pyrolysis at different substrate temperature were studied by X-ray diffraction (XRD), scan electron microscope (SEM), Raman spectrum and Uv-vis absorption spectrum. The experimental results show that the crystallinity level gets higher with increasing substrate temperature while the bandgap remains constant. This deposition method should be an effective method as the deposited film looks uniform and smooth in the SEM image. Furthermore, the photoelectrochemical activities of CdS thin films used as electrode to split water to hydrogen and oxygen were investigated. The photoelectrochemical activity increases and then decreases with increasing substrate temperature which forms a peak value at 300 °C . Under a light intensity of 187 mW/cm, the electrode deposited at 300 °C gives a saturated photocurrent of 4.1 mA/cm with increasing electrode potential. The highest energy conversion efficiency was calculated as 0.68% at electrode potential of -0.13 V (vs SCE).

关键词： CdS Hydrogen solar Photoelectrochemistry Ultrasonic spray pyrolysis (USP)

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Effects of reactant gas flow rates on the current distribution in a PEM fuel cell

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology 2006年第SUPPL. 2期28卷 601-604页

作者： Shang, De-Hua Zhang, Guang-Sheng Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

As an important performance diagnosis tool, in-situ measurement of current distribution in PEM fuel cells is helpful for better understanding of internal transport phenomena and optimization of fuel cell structures and operating parameters. With a specially developed current distribution measurement gasket, the effects of reactant gas flow rates on the current distribution in a PEM fuel cell with single serpentine flowfield were investigated. Experimental results show that insufficient hydrogen or air leads to decreased current density along the gas flow direction. Higher reactant gas flow rate favors not only the local performance but also the homogeneity of current distribution. But current distribution almost ceases to change with further increase of hydrogen flow rate when it reaches certain value.

关键词： Current distribution Fuel cell Proton exchange membrane (PEM)

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Experimental study of liquid slug velocity in horizontal pipe line

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第1期27卷 71-74页

作者： Wang, Xin Guo, Lie-Jin Zhang, Xi-Min Guo, Fu-De State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The velocities of liquid slugs in continuous slug flow were studied experimentally in a 133 m long horizontal pipeline. Measurements were performed by cross-correlating the signals of two pairs of probes installed along the pipeline. Correlations of liquid slug velocities with the mixed velocities are presented. It is found that the correlations depend on Froude numbers. At low Froude numbers, the correlation from the measurements of the upstream probes is consistent with that from the measurements of the downstream probes and both correlations agree well with the results of other researchers. But there is difference between the correlation of the upstream probes and that of the downstream probes at high Froude numbers. Compared with the experimental data of other researchers, it is expected that the velocities of liquid slugs are affected by the void fraction in liquid slugs and the evolution of the lengths of liquid slugs and elongated bubbles along pipeline. However, the wake effect may have no influence on the liquid slug velocities.

关键词： Liquid slug velocity Slug flow Slug length Two-phase flow

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Preparation of CdS photocatalyst and its performance of hydrogen production

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology 2006年第SUPPL. 2期28卷 164-168页

作者： Zhang, Xiang-Hui Jing, Deng-Wei Xing, Chan-Juan Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Cadmium sulfide photocatalyst was prepared by hydrothermal methods with one-step and two-step methods, respectively. Platinum was loaded on the surface of prepared photocatalysts and its optimal loading amount was examined. All the prepared photocatalysts were characterized by XRD, UV-Vis, XRF, SEM and TEM and their pohtocatalytic activity was evaluated by H2 evolution from water under visible light. It was found that the photocatalyst prepared by two-step showed markedly improved hydrogen production activity.

关键词： CdS Hydrogen production Photocatalyst

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Investigation on heat transfer characteristics of fully developed flow in bilaterally heated narrow annuli

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Hedongli Gongcheng/Nuclear Power engineering 2006年第SUPPL. 1期27卷 57-60页

作者： Zeng, He-Yi Qiu, Sui-Zheng Jia, Dou-Nan School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Numerical research was carried out on the convection heat transfer characteristics in bilaterally heated annular channel with narrow gap under the conditions of fully developed flow, where the inner and outer walls are heated by uniform but unequal heat fluxes. Calculation results show that the ratio of the inner wall heat flux to the outer wall heat flux has great effects on the heat transfer characteristics in bilaterally heated narrow annuli. With the increase of the inner wall heated flux, the heat transfer coefficient at the outer wall of the inner tube will decrease, while the heat transfer coefficient at the inner wall of outer tube will increase. These numerical results are in good agreement with some experimental results in open literatures. Numerical results also show that the decrease of the annuli gap will yield heat transfer deterioration during flowing in narrow annular channels.

关键词： Heat transfer

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Stability of stratified flow and slugging in horizontal gas-liquid flow

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Progress in Natural Science:Materials International 2005年第11期15卷 1026-1034页

作者： GU Hanyang and GUO Liejin (state key laboratory of multiphase flow in Power engineering, Xi’an Jiaotong University, Xi’an 710049, China) State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Xi''an 710049 China

A transient one-dimensional two-fluid model is proposed to investigate numerically the interfacial instability and the onset of slugging for liquid-gas flow in a horizontal duct. In the present model, the effects of surface tension and transverse variations in dynamic pressure are taken into account. The evolution of interfacial disturbances is displayed and compared with the linear viscous Kelvin-Helmholtz stability analyses. It shows that interfacial wave is more instable due to the non-linear effect. The model predicts well the stability limit of stratified flow in comparison with the experimental data, and also automatically tracks the onset of slugging. The results show that the initiation of hydrodynamic slugging is related to local interfacial instability. Based on the cycle of slugging, a model for slug frequency is presented, which predicts the trends of slug frequencies with gas/liquid flow rate well in comparison with the available data. The effects of physical properties on slugging have been examined. It is found that with the increase in the gas viscosity and liquid density the slugging would be inhibited, whereas, with the increase in liquid viscosity and gas density, the slugging can be promoted.

关键词： two-fluid model Kelvin-Helmholtz stability interfacial instability onset of slugging gas-liquid stratified flow.

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Study on the heat transfer of cross flow in vertical upward tubes

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2005年第10期6卷 1128-1131页

作者：胡志华杨燕华周芳德 School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200030 China State Key Laboratory of Multiphase Flow Xi’an Jiaotong Univeristy Xi’an 710049 China

A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2～3 times that ofoil when they have the same superficial velocity.

关键词： Heat transfer Cross flow Upward

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Experimental study of the hydrogen production from coal/CMC gasified in super critical water by continuous flow thermal-catalytic reaction system

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Taiyangneng Xuebao/Acta Energiae Solaris Sinica 2005年第6期26卷 874-877页

作者： Yan, Qiuhui Guo, Liejin Liang, Xing Zhang, Ximin Hao, Xiaohong Ma, Lijing State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

As coal was transported homogeneously at high pressure by adding the sodium carboxymethylcellulose (CMC), the hydrogen production from catalytic gasification of coal/CMC in supercritical water (SCW) was investigated. The experimental results showed that the molar fraction of hydrogen is higher than that in conventional gasification. H2, CO2 and CH4 are the main product gases, the higher pressure and higher CMC content is advantage of hydrogen production. Longer residence time is favorite to gasification of coal/CMC, but it is not advantage of hydrogen production from coal/CMC gasified in SCW at 20-25 MPa, 15-30 s and 650°C.

关键词： Hydrogen

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Probabilistic distribution of initial ejection state of particles in equilibrium sand transport

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2005年第4期26卷 613-616页

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

The equilibrium sand transport is simulated by Lagrange model combined with the probabilistic distributions of initial speed and angle of ejection sand grain in this paper. Five forms of the possible distributions are summarized from the previous study results published in literature. Since the macro-quantities simulated by rational distribution should be coincident well with experimental result, the rationality of the distributions can be tested by comparing the quantities simulated from these distributions with the experimental quantities. Detailed analysis indicates that the distribution of initial speed and angle of ejected grains in equilibrium sand transport should be a monotonous decline function. According to the experimental data a segmented function comprised by an exponential distribution and a normal distribution is suggested in this paper. This distributions is confirmed by further comparison with experimental data.

关键词： Distribution Ejection Equilibrium transport Sand

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Thermal boundary condition for the thermal lattice Boltzmann equation

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Physical Review E 2005年第1期72卷 016703-016703页

作者： G. H. Tang W. Q. Tao Y. L. He State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

A thermal boundary condition for a double-population thermal lattice Boltzmann equation (TLBE) is introduced and numerically demonstrated. The unknown distribution population at the boundary node is decomposed into its equilibrium part and nonequilibrium parts, and then the nonequilibrium part is approximated with a first-order extrapolation of the nonequilibrium part of the populations at the neighboring fluid nodes. Numerical tests with Dirichlet and Neumann boundary constraints show that the numerical results of the TLBE together with the present boundary schemes agree well with the analytical solutions and those of the finite-volume method.

关键词： NAVIER-STOKES EQUATION BGK MODEL HEAT-TRANSFER GAS AUTOMATA flowS SIMULATION PRESSURE VELOCITY

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