检索结果-内蒙古大学图书馆

Shape of isolated bubble in intermittent flows in horizontal straight tube

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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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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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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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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Research on optimization of the parameters for continuous anaerobic hydrogen production

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology 2006年第SUPPL. 2期28卷 174-180页

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

Orthogonal array tests were carried out to investigate the optimal temperature(T), hydraulic retention time (HRT), pH and C/N ratio of anaerobic fermentative hydrogen production using a 20 L continuous stirred-tank reactor (CSTR). The results showed that hydrogen production rate, hydrogen content, glucose utilization ratio and hydrogen yield reached the maximum of 6.00 L/h, 55.0%, 99.0%, 157.86 mL/g in appropriate conditions, respectively. The optimal pH, T, HRT and C/N ratio were 5.0, 33.5-36.5 °C, 8.34 h, 112/1.55, respectively. A confirmation experiment was carried out to verify the optimal parameters obtained by orthogonal array tests. Hydrogen production rate, hydrogen content, glucose utilization ratio and potential hydrogen yield reached the maximum of 5.66 L/h, 54.0%, 0.97, 191.18 mL/g, respectively. The results of the confirmation experiment showed that hydrogen production with the optimal parameters was more efficient than that in the orthogonal array tests, and that suggested the orthogonal array tests were successful.

关键词： Anaerobic fermentation CSTR Hydrogen production Orthogonal array test

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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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