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Nanomaterials for renewable hydrogen production,storage and utilization

Progress in Natural Science:Materials International 2012年第6期22卷 522-534页

作者： Samuel S.Mao Shaohua Shen Liejin Guo Lawrence Berkeley National Laboratory and Department of Mechanical Engineering University of California at Berkeley.BerkeleyCA 94720United States Lawrence Berkeley National Laboratory and Department of Mechanical Engineering University of California at Berkeley.BerkeleyCA 94720.United States International Research Center for Renewable Energy.State Key Laboratory of Multiphase Flow in Power Engineering.Xi'an Jiaotong University International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

An ever growing demand for energy coupled with increasing pollution is forcing us to seek environmentally clean alternative energy resources to substitute fossil *** rapid development of nanomaterials has opened up new avenues for the conversion and utilization of renewable *** article reviews nanostructured materials designed for selected applications in renewable energy conversion and *** review is based on the authors’ research,with particular focus on solar hydrogen production,hydrogen storage and hydrogen *** topics include photoelectrochemical(PEC) water splitting and photocatalytic hydrogen production, solid-state hydrogen storage,and proton exchange membrane fuel cells(PEMFCs).It is expected that the rational design of nanomaterials could play an important role in achieving a renewable energy based economy in the coming decades.

关键词： Nanomaterials Renewable energy Hydrogen production Fuel cell Hydrogen storage

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An experimental study of on-line measurement of water fraction in gas-oil-water three-phase flow

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AIP Conference Proceedings 2012年第1期1428卷 128-135页

作者： K. Chen L. J. Guo J. Ye State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China aState Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

Gas-oil-water two-or three-phase flow is widely encountered in industry, such as petroleum chemical industry, bio-chemicals, food chemicals, and mineral engineering and energy projects. Two kinds of on-line measurement technique, which are double-ring conductance sensor and double-helical capacitance sensor, for water fraction in oil-water two-phase flow and gas-oil-water three-phase flow were developed in this paper. The calibration results shows that the responses of the two sensors are good enough as the variation of water fraction. And on the other hand, it is possible that the oil and the gas regard as one phase in gas-oil-water three-phase flow by using double-helical capacitance sensor, and the ratio between water and gas has no effect with the output signal. The range of water fraction which can be measured becomes bigger and bigger because of the using of new circuit. So the capacitance sensor is better enough to measure water fraction in the three phases flow. During dynamic experiment, because of phase inversion phenomenon between oil and water, the conductance sensor outputs poorly, however the capacitance sensor performs somewhat fine. The reason for the error using capacitance sensor is the edge effect of the capacitance. The experiment results show that the edge effect of the double-helical capacitance sensor causes that the output is smaller so that the measuring water fraction is a litter larger than the actual value. And when the variation of water fraction is above 10%, the edge effect of capacitance sensor can be almost neglected. On the contrary, when the variation of water fraction is below 10%, the edge effect is so lager than the results above that it cannot be ignored. Consequently, the double-helical capacitance probe is more suitable for measuring water fraction in slug flow and oil-water emulsion, in which the results agree better with static calibration than that in bubble flow.

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Enhancement of flow-jet combined boiling heat transfer of FC-72 over micro-pin-finned surfaces

Enhancement of flow-jet combined boiling heat transfer of FC...

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作者： Zhang, Yonghai Wei, Jinjia Guo, Dong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China YanTai WanHua Group YanTai 264000 China

For highly efficient solving of the power dissipation problem of electronic components with high heat flux, experimental study of the flow-jet combined boiling heat transfer on silicon chips was conducted. Micro-pin-fins with dimensions of 30×60 μm2 and 30×120 μm2 (thickness × height) were fabricated on the chip surfaces by the dry etching technique. The experiments were made at three different cross-flow velocities Vc (0.5, 1.0, 1.5 m/s) and different jet velocities V j (0-2 m/s) with two liquid subcooling ΔTsub (25°C and 35°C). A smooth surface was also tested for comparison. The micro-pin-fins showed a considerable heat transfer enhancement due to an increase in effective heat transfer surface area caused by micro-convection around micro-pin-fins. The maximum allowable heat flux qmaxis increased and the wall superheat is decreased greatly. For a given Vc, the heat transfer enhancement is more significant as Vj increases, but the qmax increment decreases as Vc increases. The fin efficiency decreases as Vcor/and Vj increases or the heat flux q increases. The maximum q max can reach 161 W/cm2 at Vc == 1.5 m/s, Vj = 2 m/s, ΔTsub = 35°C for chip PF30-120. © 2012 by Begell House, Inc.

关键词： Heat flux

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Vertically oriented TiO_2 nanotube arrays with different anodization times for enhanced boiling heat transfer

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Science China(Technological Sciences) 2012年第8期55卷 2184-2190页

作者： XU Jia YANG MingJie XU JinLiang JI XianBing Beijing Key Laboratory of Low-Grade Energy Multiphase Flow and Heat Transfer School of Renewable EnergyNorth China Electric Power UniversityBeijing 102206China Laboratory of Advanced Materials Department of Material Science and EngineeringTsinghua UniversityBeijing 100084China

Pool boiling of saturated water on a plain Ti surface and surfaces covered with vertically-oriented TiO2 nanotube arrays(NTAs) has been *** technique of potentiostatic anodization using non-aqueous electrolytes was adopted to fabricate three types of TiO2 NTAs distinguished by their anodization *** to the bare Ti surface,the incipient boiling wall superheat on the TiO2 NTAs was decreased by 11 *** the critical heat flux and heat transfer coefficient of pool boiling on the TiO2 NTAs were higher than those from boiling on a bare Ti *** measured maximum critical heat flux and heat transfer coefficient values were 186.7 W/cm2 and 6.22 W/cm2K,*** performances for the enhancement of heat transfer by the three types of TiO2 NTAs were attributed to the different degrees of deformation in the nanostructure during ***-term performance of the nanomaterial-coated surfaces for enhanced pool boiling showed degradation of the TiO2 NTAs prepared with an anodization time of 3 hours.

关键词： TiO2 nanotube arrays pool boiling heat transfer enhancement deformation of nanostructure

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Hydrodynamic analysis and calculation of metal temperature distribution in spiral water wall of ultra supercritical tower boiler

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AIP Conference Proceedings 2013年第1期1547卷

作者： Chengwu Shen Dong Yang Danhua Yao Yufeng Zhu Xueyuan Xu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China Shanghai Boiler Works Ltd. Shanghai China

In this paper, the spiral water wall system of a 1000MW ultra supercritical tower boiler is simplified as a network system, consisting of circuits, pressure grids and connecting tubes. The establishment of the mathematical model for calculating the mass flux distribution and metal temperature in water wall is based on the mass, momentum and energy conservation equations. The water wall flow distribution and temperature profile of the boiler were computed. The result shows that the differences of outlet temperature and mass flux are small in spiral tube water wall at BMCR, 75%BMCR load and 40%BMCR load. The metal temperatures are all in the allowable ranger.

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Influence of nozzle diameter on spray characteristics and surface heat transfer dynamics in cryogen spray cooling for dermatologic laser surgery 12

Influence of nozzle diameter on spray characteristics and su...

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12th International Conference on Liquid Atomization and Spray Systems, ICLASS 2012

作者： Zhou, Zhifu Wang, Rui Wang, Guoxiang Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Engineering University of Akron AkronOH44325 United States

Cryogen spray cooling (CSC) is an effective method to minimize or even eliminate laser-induced irreversible injury to the epidermis during laser surgery of various cutaneous anomalies such as port wine stain (PWS). This paper conducts an experimental investigation of the atomization characteristics and surface heat transfer dynamics in pulsed cryogen spray cooling of epidermis by R-134a, focusing on the effect of the nozzle diameter. A Phase Doppler Particle Analyzer (PDPA) is used to measure the distributions of the diameter and velocity of the liquid droplets in the spray. The temperature of liquid droplets in spray is measured by a micro-thermocouple with a bead diameter of around 100 μm. A thin-film thermocouple of 2 μm thickness is deposited directly onto the epoxy resin substrate (which serves as the skin phantom) to monitor the variation of the surface temperature induced by the CSC. The dynamic variation of the surface heat flux and convective heat transfer coefficient in CSC can then be quantified from the measured temperatures using the Duhamel's theorem. Four nozzles with diameter ranging from 0.48 mm to 1.75 mm have been used and a systematic parametric study was conducted to illustrate the effect of nozzle diameter on spray characters and surface heat transfer dynamics. It is found that the nozzle with the smaller diameter produces finer liquid droplets and larger droplets velocity than that with the larger diameter. Furthermore, the temperature of droplets from the smaller diameter nozzle decreases faster with the spray distance. Analysis of surface heat transfer indicates that the size and velocity of liquid droplets in spray has a large effect on surface heat flux and heat transfer coefficient, with large droplets leading to high heat flux at the cooling surface. In addition, a criterion is proposed to evaluate the cooling efficiency of a given nozzle based on the variation of heat extraction from the cooling surface within the effective cooling time

关键词： Heat transfer coefficients

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Study on performance of double helical capacitance probe for water fraction measurement in multiphase flow

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AIP Conference Proceedings 2012年第1期1428卷 120-127页

作者： J. Ye L. J. Guo H. L. Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

A type of capacitance probe performance with two brass electrodes intertwined on the outer wall of insulation pipe like a double helix is investigated numerically in this paper, which can measure water fraction in air-oil-water two or three-phase flow in oil industry. The motivation of this paper is to optimize this kind of probe to improve its electric response and spatial resolution and so a 3-D numerical simulation using finite element method is employed to evaluate the effect of electrodes configuration of this capacitance probe on measuring water fraction in horizontal pipes. The electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow regime. Several parameters are considered as main variables which have an important effect on the precision of the probe, such as central angle, position angle and length of the two electrodes. From the electrostatic field analysis, lumped capacitance between the two electrodes is obtained in every different electrode geometry model and the results of each model are compared to each other in order to select a better arrangement of the electrodes that has a better response to water fraction. And by using circuit simulation method, the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the experiment. The relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the simulation. The results show that at high water fraction, the difference between numerical and measured data agrees very well.

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A numerical study of the MPS method for simulating non-newtonian free surface flows

A numerical study of the MPS method for simulating non-newto...

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23rd International Congress of Theoretical and Applied Mechanics

作者： Hao Xiang Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The moving particle semi-implicit method(MPS) is a Lagrangian particle method which is suitable for simulating surface flows *** paper couples the non-Newtonian model with the MPS method by treating the non-Newtonian ... 详细信息

关键词： A numerical study of the MPS method for simulating non-newtonian free surface flows

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Study on Performance of Double Helical Capacitance Probe for Water Fraction Measurement in multiphase flow

Study on Performance of Double Helical Capacitance Probe for...

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The 7th International Symposium on Measurement Techniques for multiphase flows

作者： J.Ye L.J.Guo H.L.Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

A type of capacitance probe performance with two brass electrodes intertwined on the outer wall of insulation pipe like a double helix is investigated numerically in this paper,which can measure water fraction in air-oil-water two or three-phase flow in oil *** motivation of this paper is to optimize this kind of probe to improve its electric response and spatial resolution and so a 3-D numerical simulation using finite element method is employed to evaluate the effect of electrodes configuration of this capacitance probe on measuring water fraction in horizontal *** electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow *** parameters are considered as main variables which have an important effect on the precision of the probe,such as central angle,position angle and length of the two *** the electrostatic field analysis,lumped capacitance between the two electrodes is obtained in every different electrode geometry model and the results of each model are compared to each other in order to select a better arrangement of the electrodes that has a better response to water *** by using circuit simulation method,the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the *** relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the *** results show that at high water fraction,the difference between numerical and measured data agrees very well.

关键词： Numerical simulation water fraction capacitance probe multiphase flow

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CaTaO2N-CaZrO3 solid solution: Band-structure engineering and visible-light-driven photocatalytic hydrogen production

CaTaO2N-CaZrO3 solid solution: Band-structure engineering an...

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作者： Wu, Po Shi, Jinwen Zhou, Zhaohui Tang, Wendong Guo, Liejin International Research Center for Solar-Hydrogen Renewable and Clean Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University 28 West Xianning Street Xi'an 710049 China

A series of CaTaxZr(1-x)O(3-x)N x solid solutions were successfully synthesized through nitriding precursors prepared by the polymerized complex method. The physicochemical properties of these multicomponent semiconductors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption-desorption isotherms, UV-visible optical absorption spectra (UV-Vis) and density functional theory (DFT) calculations. The diffraction peaks in XRD patterns gradually shifted to higher angles as x increased, indicating that CaTaxZr(1-x)O(3-x)Nx solid solutions had been formed. The absorption edges in UV-Vis spectra red-shifted monotonically as x increased, demonstrating that the band gap of the prepared photocatalysts could be precisely controlled with the adjustment of compositions. The solid solutions rendered photocatalytic H2 evolution from a formic acid aqueous solution under visible-light irradiation. The narrow band gap, sufficient crystallization, enough pore volume and large specific surface area resulted in the best photocatalytic activity of CaTa 0.8Zr0.2O2.2N0.8. Highlights: CaTaxZr(1-x)O(3-x)Nx solid solutions were synthesized by PC method. Absorption edges red-shifted monotonically as x increased. CaTa0.8Zr0.2O2.2N0.8 showed best H2 evolution. Band gap and specific surface area were both key factors. © 2012 Hydrogen Energy Publications, LLC.

关键词： Solid solutions

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