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Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

AIP Conference Proceedings 2013年第1期1547卷 432-441页

作者： Zhuqiang Yang Qincheng Bi Yong Guo Zhaohui Liu Jianguo Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

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Numerical simulation of the multi-component slurry gasification with the non-premixed combustion model

Numerical simulation of the multi-component slurry gasificat...

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2013 Spring International Conference on Material Sciences and Technology, MST-S 2013

作者： Li, Xing Xing Yi, Chun Hai Yang, Bo Lun Zhang, Yong Men, Chang Gui He, Gen Liang Xu, Hong Dong Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Northwest Research Institute of Chemical Industry Xi'an Shaanxi 710049 China

ISBN: (纸本)9783037857090

Considering the volumetric reactions and particle surface reactions in an entrained flow gasifier, the non-premixed combustion model based on the wet particles combustion method is adopted to simulate the multi-component slurry gasification process with FLUENT software. The velocity, temperature and concentration profiles of the gas products in the gasifier are obtained. Simulated results agree well with the commercial data, which verified the validity and applicability of the present model. Simultaneously, the reaction subarea in the gasifier has turned out to be obvious, the water evaporation, volatiles cracking and combustion reactions mainly appear in the jet region of the gasifier, the char gasification mainly appear in the freeboard region, but few reactions appear in the recirculation region. Moreover, with the increase of the mass fraction of the multi-component slurry, the content of the syngas at the gasifier outlet increases, while with the oxygen carbon atom ratio increasing, the syngas yield is rising early but declining later. © (2013) Trans Tech Publications, Switzerland.

关键词： Surface reactions

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Stability analysis of a square rod bundle sub-channel in supercritical water reactor

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AIP Conference Proceedings 2013年第1期1547卷 181-189页

作者： Wang Hai-jun You Ting Zhang Lei Gu Hong-fang Luo Yu-shan Bian Ji-lian State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University Xi'an 710049 China

Extensive investigations on the flow and heat transfer behavior in SCWR fuel assembly have been undertaken worldwide. However, stability analysis of supercritical water in the sub-channels of tight lattices is still lacking. In this paper, the flow stability of a fuel bundle channel with square pitches has been analyzed using commercial CFD code-ANSYS Fluent. Typical dynamic instability of Density Wave Oscillation (DWO) has occurred in heated channel containing fluids at supercritical pressure. A further discussion about the impacts of various operational parameters (e.g. power input, system pressure, mass velocity, inlet temperature, etc) shows that the system becomes more stable as system pressure and/or mass flow rate increases. An increase in inlet temperature also has a stabilizing effect on the system.

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Sensitive measurement of trace mercury using low pressure laser-induced plasma

Sensitive measurement of trace mercury using low pressure la...

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作者： Wang, Zhenzhen Deguchi, Yoshihiro Kuwahara, Masakazu Zhang, Xiaobo Yan, Junjie Liu, Jiping State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China Graduate School of Advanced Technology and Science University of Tokushima Tokushima 770-8501 Japan

The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results. © 2013 The Japan Society of Applied Physics.

关键词： Laser induced breakdown spectroscopy

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Enhancement of Photoelectrochemical Performance by Doping Tantalum Ions in Hematite （a-Fe2O3） Nanorod Photoanodes

Enhancement of Photoelectrochemical Performance by Doping Ta...

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International Conference on Nanoscience & Technology,China 2013(ChinaNANO 2013)

作者： Yanming Fu Liang Zhao Shaohua Shen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Ta-doped hematite (α-Fe 2 O 3 ) nanorod array electrodes were successfully prepared on FTO substrates using the conventional method by adding TaCl 5 in the aqueous solution directly. With the increasing of TaCl 5 dopant content, the photoelectrochemical (PEC) activity of the Ta-dopedα-Fe 2 O 3 nanorod films firstly increased and then decreased. Compared with the undoped α-Fe2O3 nanorod films, the optimal content of Ta-doped hematite sample showed about 3.5 times higher photoelectrochemical activity under the irradiation of solar light (AM 1.5, 100 mW·cm-2), as high as 0.53 mA·cm -2 at 0.5V vs. SCE(saturated calomel electrode) in 0.5 M Na 2 SO 4 . In order to analyze the mechanism of tantalum ions in changing the photoelectrode performance, all films were characterized by Raman spectra, UV-visible spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum(EDX) and X-ray photoelectron spectroscopy (XPS). The results reveal that at low Ta doping contents, small amount of Ta is dopedinto the nanorods of α-Fe 2 O 3 films and the photocurrent improvement is mainly attributed to the reduced electron-hole recombination in the α-Fe 2 O 3 nanorod *** at high Ta doping contents, superfluous Ta dopant forms a thick tantalum oxide layer and the layer completely covers the nanorods of α-Fe 2 O 3 films. This special surface structure reduces the number of photogenerated electrons (or holes) and weakens the charge transfer ability to raise the surface charge recombination of α-Fe 2 O 3 nanorods, leading to the decreased photoelectrochemical activity.

关键词： α-Fe 2 O 3 , nanorods, photoelectrochemical, doping

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EROSION PREDICTION OF LIQUID-PARTICLE TWO-PHASE flow IN PIPE ELBOWS VIA CFD-DEM COUPLING METHOD

EROSION PREDICTION OF LIQUID-PARTICLE TWO-PHASE FLOW IN PIPE...

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2013中国工程热物理学会多相流学术年会

作者： J.K.Chen Y.S.Wang S.Han Y.L.Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Erosion is a wear damage caused by the impact of small and loose moving particles to the surface and erosion damage is commonly encountered in petroleum exploitation and transportation engineering,especially such pipeline components as tees,elbows and reducers in long-distance crude-oil transmission *** 1990,Humphrey [1] presented an extensive review on erosion and pointed out that the particle incidence speeds,incidence angles and material-related aspects have great influence on surface erosion in ***,the theoretical research on erosion is still in development and no single erosion model or equation could be found for general and practical uses [2].Therefore,the study on the particle motion characteristics and erosion properties and the accurate prediction of erosion damage seem to have important academic significance and engineering application *** recent decade,Computational Fluid Dynamics(CFD) method has behaved as a serviceable approach to predict fluid flow and a supplementary means to study ***,most of the literature on CFD-based erosion research ignores the effect of particles to fluid flow and the impact among particles,which is a one-way or two-way coupling method that is only suitable for the cases with lower particle volume *** this study,the Discrete Element Method(DEM) has been applied in combination with CFD,in which the interaction of liquid-particle,particle-particle,and particle-wall are taken into *** volume averaging continuity and momentum equations as well as the standard k-ε model for turbulent have been adopted for modeling of the continuous carrier fluid *** motion of particles has been modeled as a discrete phase,described by the Newton's laws of motion on an individual *** interaction between fluid and particles has been expressed by the Di Felice Drag Model [3].When a particle contacts with other particles or wall,the soft-sphere model [4] is *** erosion pr

关键词： Liquid-particle two-phase flow Erosion Elbow CFD-DEM Numerical simulation

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Interaction contributions in thermal conductivity of three-dimensional complex liquids

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AIP Conference Proceedings 2013年第1期1547卷 173-180页

作者： Aamir Shahzad Mao-Gang He State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University and Department of Physics Government College University Faisalabad (GCUF) Allama Iqbal Road 38000-Faisalabad Pakistan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

This work generalizes Evans' homogenous nonequilibrium molecular dynamics (HNEMD) algorithm for computing the thermal conductivity of strongly-coupled complex (dusty) plasma liquids (SCCDPLs) described by the Yukawa potential. The effects of external field strength along with different screening strengths on the conductivity of Yukawa liquids have investigated using HNEMD simulations. We have carried out some more linear and nonlinear molecular dynamics calculations of the thermal conductivity, and the obtained simulation results of SCCDPLs are presented for various plasma coupling and screening parameters. Our calculations show that Yukawa liquid exhibits a non-Newtonian behavior that the thermal conductivity increases with increasing field strength which explains interaction contributions in Yukawa conductivity, for the first time. The simulation results obtained with different external filed strengths are in reasonable agreement with earlier simulation results and with reference set of data showed deviations within less than ±10% for most of the present data point. It is shown that new simulations extended the range of field strength (0.001≤F*≤0.1) used in the earlier studies in order to find out the size of the linear regimes and to explain the nature of nonlinearity of SCCDPLs.

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Graphitic carbon nitride modified by silicon for improved visible-light-driven photocatalytic hydrogen production

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Nanostructured Materials and Nanotechnology V - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012

作者： Wu, Po Shi, Jinwen Chen, Jie Wang, Bin 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

ISBN: (纸本)9781118205976

In this work, composites of silica and graphitic carbon nitride (g-C3N4) were conveniently synthesized through polymerization of melamine and ethyl silicate. Some basic physicochemical properties of these metal-free photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), Fourier transform infrared spectrometer (FTIR) spectra, transmission electron microscope (TEM), UV-visible diffuse reflectance spectrum and N2 adsorption-desorption measurement. The XRD patterns of all the prepared materials were dominated by the characteristic (002) peak at 27.5° of a graphitic structure, indicating that the induced Si did not destroy the crystal structure of g-C3N4). As the initial molar ratio of Si to C increased, enhanced photocatalytic activity was observed for H2 evolution from a triethanolamine aqueous solution under visible-light irradiation over the series of composites. It was proved that the introduction of Si resulted in large surface area, which is favorable for reactant-transfer and charge-migration, beneficial for photocatalysis.

关键词： X ray diffraction

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Numerical research of dynamic characteristics in tower solar cavity receiver based on step-change radiation flux

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AIP Conference Proceedings 2013年第1期1547卷 746-757页

作者： Zhengwei Chen Yueshe Wang Yun Hao Qizhi Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China and Beijing Institute of Space Long March Vehicle 100076 Beijing China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

The solar cavity receiver is an important light-energy to thermal-energy convector in the tower solar thermal power plant system. The heat flux in the inner surface of the cavity will show the characteristics of non-continuous step change especially in non-normal and transient weather conditions, which may result in a continuous dynamic variation of the characteristic parameters. Therefore, the research of dynamic characteristics of the receiver plays a very important role in the operation and the control safely in solar cavity receiver system. In this paper, based on the non-continuous step change of radiation flux, a non-linear dynamic model is put forward to obtain the effects of the non-continuous step change radiation flux and step change feed water flow on the receiver performance by sequential modular approach. The subject investigated in our study is a 1MW solar power station constructed in Yanqing County, Beijing. This study has obtained the dynamic responses of the characteristic parameters in the cavity receiver, such as drum pressure, drum water level, main steam flow and main steam enthalpy under step change radiation flux. And the influence law of step-change feed water flow to the dynamic characteristics in the receiver also has been analyzed. The results have a reference value for the safe operation and the control in solar cavity receiver system.

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Enhanced Photosynthetic Hydrogen Production of Rhodobacter sphaeroides with Deactivation of spbA and hupSL

Enhanced Photosynthetic Hydrogen Production of Rhodobacter s...

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第五届世界氢能技术大会(WHTC2013)

作者： Xueqing Wang Honghui Yang Yang Zhang Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University China

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