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Modelling of water transport in PEM fuel cell

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2010年第9期31卷 1504-1507页

作者： Xu, Cheng-Jie Zhang, Guang-Sheng Liu, Hong-Tan Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Dept. of Mechanical and Aerospace Engineering University of Miami Coral Gables FL 33124 United States

A mixed-domain, two-phase flow, non-isothermal model is developed to study the water transport phenomena, which has significant effects on the performance of PEM fuel cells. Modelling results show that: the total water concentration is decreasing along the channel in anode, while it is increasing in cathode, flooding is most likely to occur at the end of cathode flow channel;liquid water in cathode GDL presents opposite distribution at high current density and low current density, the saturation of liquid water is decreasing from inner side to outer side across the GDL at low current density while it is increasing at high current density.

关键词： Two phase flow

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Hydrogen Production by CMC Gasification in Supercritical Water

Hydrogen Production by CMC Gasification in Supercritical Wat...

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IEEE PES Asia-Pacific power and Energy engineering Conference (APPEEC)

作者： Xiaohong Hao Liejin Guo Ximin Zhang School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9781424448128;9781424448135

Hydrogen production by biomass supercritical water gasification is about to develop in the future because the process is closed and clean with high gasification efficiency in addition. Low concentration sodium carboxymethylcellulose (CMC) (2-3% mass fraction) can be mixed with particulate biomass and water to form a uniform and stable viscous paste which can be pumped to the continuous high-pressure reactor. In this paper, the supercritical water gasification of CMC was investigated in the tube flow apparatus to produce gas products consisting essentially of H 2 , CO, CH 4 and CO 2 .

关键词： Hydrogen Production Inductors Biomass Temperature Feeds Resistance heating Regulators Cooling Atmospheric measurements

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Comparisons of four quench methods for high temperature Syngas‐Exergy Analyses

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AIP Conference Proceedings 2010年第1期1207卷 674-679页

作者： Y. H. Liu W. Chen D. F. Che Z. D. Cao aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China and School of Energy and Power Engineering Xi’an Jiaotong University China bSchool of Science Xi’an University of Architecture and Technology China

Entrained flow slagging gasifiers have been found in many applications, one of which is IGCC. The quench of high temperature syngas from first stage of entrained flow slagging gasifiers is of great importance for the availability of gasifiers, and it influences the economical running of utilization system. Four kinds of quench methods including water quench, gas quench, radiant quench and chemical quench, are investigated by Gibbs free energy minimization and exergy analyses. The exergy distributions of the streams into and out of each quench system are obtained. The results show that exergy loss of water quench is the biggest, and the exergy loss of chemical quench is the least and can be neglectable. The exergy losses of the other two quench methods are comparable, which are only 1/3 smaller than that of water quench. Chemical quench not only features in lower oxygen consumption as well as a higher cold gas efficiency, but also has high exergy efficiency.

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Pressure Drop for Oil‐Water Two‐phase flow in Horizontal Pipe

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AIP Conference Proceedings 2010年第1期1207卷 665-673页

作者： W. H. Liu L. J. Guo aTubular Goods Research Center of China National Petroleum Corporation Xi’an China bState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

Pressure drops were measured during the co‐current flow of a mechanical oil and tap water in 40 mm inner diameter horizontal test section made from organic glass. Measurements is conducted were made for the oil superficial velocity ranges from 0.04 to 1.2 m/s and the water superficial velocity from 0.04 to 2.2 m/s. The volume fraction of water in the oil‐water mixture changes from 0.05 to 0.976. The frictional pressure loss of oil‐water two‐phase flow was also studied experimentally and theoretically. The main finding is the frictional pressure loss of oil‐water two‐phase flow in flow ranges corresponding to flow pattern. Two fluid model was explored to calculate the frictional pressure loss for stratified flow pattern. Homogeneous model was used to predict the fictional pressure loss for oil‐dispersed stratified, oil‐dispersed and oil annular flow regimes. For three‐layer flow regime, a correlation between flow parameters and the two‐phase pressure drop reference to water phase was proposed. The model predictions are in good agreement with experiment data.

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Numerical Study of Drop Interface Deformation and Breakup in Shear flow

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AIP Conference Proceedings 2010年第1期1207卷 877-882页

作者： C. Z. Lin L. J. Guo X. X. Han aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China bPetroleum Exploration and Production Research Institute China cShengli Oil field China

This paper presents numerical simulation results of the deformation and breakup of an isolated liquid drop suspended in an ambient, immiscible viscous fluid under shear flow. The model predicting the dynamic behavior of the drop is based on a diffuse interface method. The interface between the two fluids is tracked by an order parameter, namely the mass concentration. The fully transient, three dimensional Navier‐Stokes equations for an incompressible fluid are solved by a projection method on a fixed Cartesian grid which the interface moves through to ensure accurate calculation of the surface evolution. Surface tension effects are incorporated into the model through a modified stress. This paper focuses on steady shape analysis and the end pinching mechanism of drop breakup. The numerical results of drop deformation and breakup show very good agreement with theoretical analysis and experimental observations, which indicate that the diffuse interface method can successfully capture the main behavior of the drop deformation and breakup Detailed instructions for typing your article are given in the following.

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Investigation on the mechanism of abnormal heat transfer of supercritical pressure water in vertically‐upward tubes in the large specific heat region

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AIP Conference Proceedings 2010年第1期1207卷 531-536页

作者： J. G. Wang H. X. Li B. Guo S. Q. Yu Y. Q. Zhang T. K. Chen aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China bCollege of Energy Xi’an University of Science and Technology Xi’an 710054 China

The heat transfer characteristics of water at supercritical pressures in a vertically‐upward internally‐ribbed tube are investigated experimentally to investigate the mechanism of abnormal heat transfer of supercritical pressure water in the so‐called large specific heat region. One kind optimized internally‐ribbed tube is used in this study. The tube is made of SA‐213T12 steel with an outer diameter of 31.8 mm and a wall thickness of 6 mm and the mean inside diameter of the tube is measured to be 17.63 mm. According to experimental data, the characteristics and mechanisms of the heat transfer enhancement and also the heat transfer deterioration of supercritical pressure water in the large specific heat region are discussed respectively. The heat transfer enhancement of the supercritical pressure water in the large specific heat region is believed to be a result of combined effect caused by the rapid variations of thermophysical properties of the supercritical pressure water in the large specific heat region, and the same is true of the heat transfer deterioration. The drastic changes in thermophysical properties near the pseudocritical points, especially the sudden rise in the specific heat of water at supercritical pressures, may result in the occurrence of the heat transfer enhancement, while the covering of the heat transfer surface by fluids lighter and hotter than the bulk fluid makes the heat transfer deteriorated eventually and explains how this lighter fluid layer forms. It is also found that the heat transfer deterioration of water at supercritical pressures is similar to the DNB (departure from nucleate boiling) at subcritical pressures in mechanism.

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Numerical simulation of subcooled boiling water at low pressure incorporating homogeneous MUSIG model

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AIP Conference Proceedings 2010年第1期1207卷 986-991页

作者： E. F. Chen Y. Z. Li X. H. Cheng Lei Wang aSchool of Energy and Power Engineering Xi’an Jiaotong University China bState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China cSchool of Energy and Power Engineering Xi’an Jiaotong University China dSchool of Energy and Power Engineering Xi’an Jiaotong University China

Applying a three‐dimensional two‐fluid model coupled with homogeneous MUSIG approach, numerical simulations of subcooled water at low pressure were performed on the computational fluid dynamics code CFX‐10 with user defined FORTRAN program. A modified bubble departure diameter correlation based on the Unal semi‐mechanism model was developed. The water boiling flow experiments at low pressure in vertical concentric annulus from reference were used to validate the models. Good quantitative agreement with the experimental data is obtained, including the local distribution of bubble diameter, void fraction, axial liquid and vapor velocity. The results indicate that local bubble diameter first increases and then decreases due to the effect of bubble breakup and coalescence, and has the maximum bubble diameter along the radial direction. Moreover, the peak void fraction phenomenon in the vicinity of the heated wall is predicted at low pressure, which is developed due to the surface tension between vapor bubbles and heated wall.

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Numerical Simulation of Low Pressure Natural Gas Injector

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AIP Conference Proceedings 2010年第1期1207卷 961-967页

作者： D. T. Chong G. S. Wu S. Q. Liu J. J. Yan J. P. Liu aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China bSouthwest Petroleum University China cOil & Gas Technology Research Institute PetroChina Changqing Oilfield Company China

The maximum total recovery from all gas wells are highly desired to be got and the production is to be maintained when the gas well reaches the end of its economic life. Although the injector has been known for about one century, sparse investigations have been performed on the injector of natural gas, and no structural optimization on the natural gas injectors has been reported. In the present paper, the structural parameters of natural gas injectors was optimized numerically with the motive pressure ranging from 2.5 to 3.5 MPa, induced pressure ranging from 0.5 to 1.5 MPa and discharged pressure being 1.5 MPa. The numerical results showed that the optimal values of diffuser gradient, mixing tube length to diameter ratio, mixing chamber length to diameter ratio and mixing chamber gradient were 40, 5, 0 and 0.25, respectively. The performance of optimized injectors was also investigated numerically. The motive natural gas flowrate increased linearly with increase of motive pressure and was independent of induced pressure. The induced flowrate and entrainment ratio of natural gas were both increased with the increase of induced pressure.

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Experimental Study on the Treatment of low C/N ratio disposal of sewage with BAF

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AIP Conference Proceedings 2010年第1期1207卷 157-161页

作者： W. J. Wang T. Ma W. Cheng aKey Laboratory of Northwest Water Resources and Environmental Ecology of Education Ministry Xi’an University of Technology Xi’an 710048 China bState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiao tong University China

The Biological Aerated Filter (BAF) is a simple, high‐efficient, low‐consumptive for new biological membrane method correspond to the situation of china, will be one of the main technical measures to solve the progressive deterioration of water environment problem faced china especially medium and small towns. This paper focuses on the experimental study and mechanism analysis in which the up flow, cocurrent gas‐water, single‐stage BAF was adopted on treatment domestic wastewater, the results showed that BAF has good performance in treating domestic sewage, and it had steady treatment effect with different pollution loads.

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A MEMS density sensor based on mircro-rectangular cantilever

A MEMS density sensor based on mircro-rectangular cantilever

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International Conference on Mechanic Automation and Control engineering (MACE)

作者： Libo Zhao Zhuangde Jiang Enze Huang Zhigang Liu State Key Laboratory of Manufacturing Systems Engineering Xi'an Jiaotong University Xi'an China State Key Laboratory of Multiple Flow in Power Engineering Xi'an Jiaotong University Xi'an China

A rectangle cantilever-type micro density sensor was researched based on MEMS (Micro Electro-mechanical System) technology. A Ti-Pt-Au coil and a Wheatstone full bridge were made on the top of the rectangle cantilever-type sensitive chip. The sensitive chip was placed in uniform strong magnetic field. The resonant frequency of the sensitive chip was changed with the change of the AC current's frequency. The resonant frequency of rectangle cantilever could be measured through the Wheatstone full bridge circuit and lock-in amplifier, and then the fluid density associated with the resonant frequency of the sensitive chip could be calculated. The static analysis, modal analysis, a first-order and third-order harmonic response analysis of the rectangle cantilever were performed with ANSYS software. The best locations of the four force-sensitive resistor of Wheatstone bridge were studied.

关键词： Micromechanical devices Bridge circuits Resonant frequency Magnetic sensors Magnetic field measurement Harmonic analysis Performance analysis Sensor systems Coils Density measurement

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