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Research on optimization of the parameters for continuous anaerobic hydrogen production

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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Measurement of saturated liquid density of dimethyl ether

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第5期27卷 748-750页

作者： Wu, Jiang-Tao Wang, Bin Yuan, Le-Ming Liu, Zhi-Gang State Key Lab of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A new vibrating tube densimeter was developed with a precision of better than ±0.5 kg/m3. Using this apparatus, the saturation liquid density of dimethyl ether was measured from 233.15 K to 320.15 K, and the max relative expanded uncertainty was 0.34%(coverage factor k = 2). The experimental data of this work were correlated as a polynomial function of the temperature with the published data of our previous work. The average and maximum relative deviation were 0.13% and 0.37%, respectively.

关键词： Dimethyl ether Saturation liquid density Vibrating tube

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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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Experimental measurement of the wall shear stress in horizontal air-water bubbly flow

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Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics 2006年第3期20卷 81-84页

作者： Su, Yu-Liang Zhang, Ming-Yuan Yang, Jian Hou, Hong-Ning Zhu, Xian-Ran Dept. of Petroleum Engineering China University of Petroleum Dongying 257061 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Experiments were carried out to measure the wall shear stress (WSS) of air-water bubbly flow in a horizontal tube with 35mm I.D. with TSI-1268w hot-film probes, and the circumferential distributions of the WSS in developed regions were obtained. The measurement shows that the addition of gas into the flows increases the WSS at the bottom wall, while decreases the WSS at top wall where the bubble population is high. With an increase of gas flow rate the amount of WSS decrease at the top wall is small, while the increase of WSS at the middle and bottom wall is apparent.

关键词： Bubbly flow Horizontal tube Hot-film measurement Wall shear stress

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Study of the intensified heat transfer of longitudinally ridged internal-finned tubes

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Reneng Dongli Gongcheng/Journal of engineering for Thermal Energy and power 2006年第3期21卷 283-286页

作者： Wu, Feng Lin, Mei Tian, Lin Wang, Qiu-Wang State Key Laboratory of Power Engineering Multiphase Flows Xi'an Jiaotong University Xi'an 710049 China

Through experiments and numerical simulation methods a study has been conducted of the characteristics of convection heat exchange of ridged internal-finned tubes and a comparison of the above characteristics with the flow and heat transfer characteristics of straight internal-finned tubes is performed. The experimental results indicate that the heat exchange characteristics of ridged internal-finned tubes are better than those of straight internal-finned tubes in terms of intensified heat transfer performance, but at the same time there is a corresponding increase in flow resistance. Through the adoption of a turbulent flow model capable of realizing k-ε equation, the flow and heat transfer process of ridged internal-finned tubes have been simulated. The calculation results are in good agreement with the experimental ones. The calculation results indicate that the periodical ridges inside the finned tubes have changed the distribution of the inner-flow fields and temperature ones. Relative to the straight internal-finned tubes, a secondary vortex flow has emerged, which is conducive to an intensified heat exchange and plays a definite destructive role to the flow boundary layer. Meanwhile, by increasing the turbulent kinetic energy of the flow field, the temperature gradient in the neighborhood of the heat exchange wall surfaces has been enhanced, contributing to an intensification of heat transfer.

关键词： Forced convection Heat transfer characteristics Intensified heat transfer Ridged internal-finned tube Secondary vortex flow

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Investigation on the flow distribution characteristics of a water-wall intermediate header at a supercritical pressure

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Reneng Dongli Gongcheng/Journal of engineering for Thermal Energy and power 2006年第3期21卷 299-302页

作者： Zhu, Yu-Qin Bi, Qin-Cheng Chen, Ting-Kuan State Key Laboratory of Power Engineering Multi-Phase Flow Xi'an Jiaotong University Xi'an 710049 China

An investigation was conducted of the flow distribution characteristics of distribution header water-wall tubes under a supercritical pressure for a home-made 600 MW once-through boiler. The test parameters can be listed as follows: pressure p=23-25 MPa, mass flow rate G=400-1200 kg/(m2·s), working medium temperature t=10-400°C. An experimental study has been conducted of the impact of working medium pressure, mass flow rate and working medium temperature on the vertical water-wall tube flow distribution characteristics of the distribution header. The test results show that with an increase in mass flow rate, the uniformity of flow distribution among the vertical water-wall tubes could be enhanced. The non-uniformity of flow distribution will undergo a step increase near the quasi-critical points. Moreover, with an increasing pressure, the above-mentioned step increase will become weaker. By employing a discrete model of the parallel-connected branch tubes of the distribution header, the flow distribution among the distribution header vertical water-wall tubes was calculated and the calculation results are in good agreement with the test ones.

关键词： Distribution header Once-through boiler Supercritical pressure Vertical water-wall tubes

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Pressure-velocity coupling algorithm on non-orthogonal non-staggered grid

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Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics 2006年第1期23卷 93-96页

作者： Xie, Gong-Nan Wang, Qiu-Wang Zhang, Dong-Sheng Tao, Wen-Quan State Key Laboratory of Multi-phase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this paper, a new numerical procedure is proposed for the steady flow of a viscous, incompressible fluid based on SIMPLER algorithm on a non-orthogonal non-staggered grid, together with Cartesian velocity components as dependent variables in the momentum equations. The main feature of the algorithm is that the pressure and pressure correction equations are obtained by explicitly treating pressure cross-derivatives terms in interface contravariant velocities. A collocated arrangement of variables is introduced on numerical grids, and the cell face velocities are calculated by the momentum interpolation. It is proved that this algorithm can be effectively used to simulate fluid flow and heat transfer in complex geometry, by the validation calculation of flow inside branching channel.

关键词： Incompressible flow

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