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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Tao, Y.B. He, Y.L. State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9780791802908

In present paper, a two-dimensional numerical model for the coupled heat transfer process in the solar collector tube was developed and the unified dimensionless governing equations were derived. The full field computation method was adopted to deal with the fluid-solid conjugated heat transfer problem. The effects of Ra numbers and tube diameter ratio on the heat transfer and fluid flow performance were numerically analyzed under the constant heat flux conditions. The distributions of flow field, temperature field, local Nu and local temperature gradient were examined. The results show that when Ra is larger than 105, the effects of nature convection must be taken into account. Due to the effect of the nature convection, along the θ direction, the temperature in the cross-section decreases and the temperature gradient on the inner tube surface increases at first. When θ is near to π, the temperature and temperature gradients would present a converse variation. The local Nu on the inner tube surface increases along θ direction until it reaches a maximum then it decreases again. Due to the existing of the nature convection vortexes, the temperature distributions in some cross-sections present fluctuations along the r direction. Copyright © 2009 by ASME.

关键词： Heat flux

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Study on particle and photonic flux distributions in a magnetically stirred photocatalytic reactor

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Journal of Photonics for Energy 2015年第1期5卷

作者： Ren, Yuxun Jing, Dengwei Xi'An Jiaotong University International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering 28 Xianning West Road Xi'an Shaanxi710049 China

When dispersed in water, nanoscale photocatalysts can aggregate into microscale secondary particles due to their high surface energy. The interaction between the incident photons and the aggregated particles is expected to be significantly changed due to their comparable length scales. Hydrodynamics of the particles after aggregation and the resultant photonic flux distributions in slurry photocatalytic reactors are therefore essential. The magnetically stirred photocatalytic reactor is compact and simple for fabrication, and therefore can be readily employed in lab-scale photocatalytic tests. However, studies toward its optimization are rare. In our study, the photocatalyst distribution was simulated using a Eulerian-Lagrangian approach, while the evolution of free liquid surface led by magnetic stirring was modeled by volume of fluid method. Subsequently, based on the photocatalyst distribution, the photonic flux distribution was obtained through a mean free path-based Monte Carlo method. Outcomes suggest that at a stirring speed of 900 rpm, the 10 μm particles can be well suspended, and a moderate free liquid surface will also be present. Moreover, under sufficient stirring, larger catalyst particles are more likely to be densely distributed in the outer region, which contributes to an increase in the overall photonic absorption even higher than the one with evenly distributed photocatalysts. © The Authors.

关键词： Computational fluid dynamics

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Experimental study of nitrogen oxide emissions in a circulating fluidized bed

Experimental study of nitrogen oxide emissions in a circulat...

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20th International Conference on Fluidized Bed Combustion

作者： Liu, R.W. Zhou, Q.L. Hui, S.E. Xu, T.M. State Key Laboratory of Power Engineering Multiphase Flow Department of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

The experimental study was carried out on the emission characteristics of nitrogen oxide in a 0.3MW circulating fluidized bed as well as analysis of the formation and destruction mechanism of nitrogen oxide. Several variables associated with the combustion system were investigated in the experiment, which include bed temperature, excess air, primary-to-secondary air ratio, and coal species. It is found that the NOx emissions decrease along the height of the furnace, while the N2O emissions increase continuously. More NOx emissions and less N2O emissions are generated as the bed temperature increases. It is also illustrated that an increase of air stoichiometry leads to a significant NOx increase and an obvious N2O increase. And air staging is proved to be an effective way to control the nitrogen oxide emissions in the fluid bed. Besides, it is also shown in the experiment that the concentration of NOx and N2O is higher during the combustion of anthracite than that during the combustion of bituminous.

关键词： Nitrogen oxides

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Vapor-liquid equilibrium of H2/CO2and H2/N2/CO2mixture, the liquefaction technology related to the supercritical water gasification products 8

Vapor-liquid equilibrium of H2/CO2and H2/N2/CO2mixture, the ...

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8th International Conference on Smart and Sustainable Technologies, SpliTech 2023

作者： Wu, Hongtu Jin, Hui Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Shaanxi Xi'an710049 China

ISBN: (纸本)9789532901283

In this paper, the dew point and liquid phase composition of H2/CO2 and H2/CO2/N2 mixtures at phase equilibrium calculated by PR-BM equation and Van Der Waal mixing rule with commercial MATLAB software are introduced, it is of theoretical significance for the wide application of the products of supercritical water gasification. First, the results obtained by the self-programming code are verified with the experimental data, the experimental data and simulation results of two kinds of CO2/H2 mixtures and two kinds of CO2/N2/H2 mixtures were compared. The average percentage deviation was 2.69%, 4.05%, 2.22%, 1.20%, respectively. Thus the absolute deviations of the mixtures are within the acceptable range, therefore, the model proposed in this paper can well predict the dew point of the mixtures composed of H2/CO2 or H2/CO2/***, the dew point and the CO2 content in the liquid phase of common H2/CO2 and H2/CO2/N2 vapor mixtures in supercritical water gasification products were predicted, and a series of analysis and discussion were conducted on the predicted results finally. © 2023 University of Split, FESB.

关键词： Carbon dioxide

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A Hydrodynamic Modei for Slug Frequency in Horizontal Gas-Liquid Two-Phase flow

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Chinese Journal of Chemical engineering 2003年第5期11卷 508-514页

作者：刘磊孙贺东胡志华周芳德 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.

关键词： gas-liquid flow two-phase flow interfacial wave hydrodynamic model slug frequency

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TiO_(2) nanorods based self-supported electrode of 1T/2H MoS_(2) nanosheets decorated by Ag nano-particles for efficient hydrogen evolution reaction

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Chinese Chemical Letters 2023年第11期34卷 355-359页

作者： Changzheng Lin Yunpeng Liu Yaxing Sun Zhenyu Wang Hao Xu Mingtao Li Jiangtao Feng Bo Hou Wei Yan Department of Environmental Science&Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Physics and Astronomy Cardiff UniversityThe ParadeCardiffCF243AAWalesUnited Kingdom State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China International Research Center for Renewable Energy(IRCRE) State Key Laboratory of Multiphase Flow in Power Engineering(MFPE)Xi’an Jiaotong UniversityXi’an 710049China

Molybdenum disulfide(MoS_(2))has shown significant promise as an economic hydrogen evolution reaction(HER)catalyst for hydrogen generation,but its catalytic performance is still lower than noble metalbased ***,a silver nanoparticles(Ag NPs)-decorated 1T/2H phase layered MoS_(2) electrocatalyst grown on titanium dioxide nanorod arrays(Ag NPs/1T(2H)MoS_(2)/TNRs)was prepared through acid-tunable ammonium ion *** advantage of MoS_(2) layered structure and crystal phase controllability,as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs exhibited ultrahigh HER ***-proposed strategy combines facile hydrogen desorption(Ag NPs)with efficient hydrogen adsorption(1T/2H MoS_(2))effectively circumventes the kinetic limitation of hydrogen desorption by 1T/2H MoS_(2).The as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs electrocatalyst exhibited excellent HER activity in 0.5 mol/L H2SO4 with low overpotential(118 mV *** hydrogen electrode(RHE))and small Tafel slope(38.61 mV/dec).The overpotential exhibts no obvious attenuation after 10 h of constant current ***-principles calculation demonstrates that as-prepared 1T/2H MoS_(2) exhibit a large capacity to store *** protons can be subsequently transferred to Ag NPs,which significantly increases the hydrogen coverage on the surface of Ag NPs in HER process and thus change the rate-determining step of HER on Ag NPs from water dissociation to hydrogen *** study provides a unique strategy to improve the catalytic activity and stability for MoS_(2)-based electrocatalyst.

关键词： Molybdenum disulfide Silver nanoparticles Hydrogen evolution reaction Density functional theory Hydrogen spillover

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Shock tube study on auto-ignition characteristics of kerosene/air mixtures

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Chinese Science Bulletin 2011年第13期56卷 1399-1406页

作者： ZHANG YingJia HUANG ZuoHua WANG JinHua XU ShengLi State Key Laboratory of Multiphase Flow in Power Engineering Xi' an Jiaotong University Xi' an 710049 China Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China

Ignition delay times are obtained for kerosene/air mixtures behind the reflected shock waves at temperatures between 1445 and 1650 K,at a pressure of 0.11 MPa and an equivalence ratio of 1.0.A nebulization device with Laval nozzle is used to nebulize kerosene and form an aerosol phase,which evaporates and diffuses rapidly behind the incident shock *** auto-ignite behind the reflected shock *** ICCD is used to visualize the kerosene/air mixture's ignition *** mixture's ignition intensity increases with increase in initial *** and irregular flames exist below 1515 K while plane and discontinuous flames exist over 1560 *** delay times decrease with increase in initial *** data shows good agreement with results reported previously in the literature.A new surrogate (consisting of 10% toluene,10% ethylbenzene and 80% n-decane) is proposed for *** et al.'s mechanism is used to simulate the ignition of kerosene with calculations agreeing well with the experimental *** sensitivity of reaction H+O2 <=>OH+O,which shows the highest sensitivity to the ignition delay time,increases with an increase in *** chain breaching reaction of CH3 with O2 accelerates the total reaction rate and the H-atom abstraction of n-decane controls the total reaction *** rate of production and instantaneous heat production indicate that two reactions,H+O2 <=>OH+O and O+H2 <=>OH+H,are the key reactions to the formation of OH radicals,as well as the main endothermic ***,the reaction of R3 is the main heat release reaction during *** structure analysis shows that initial pressure is increased slightly as CO and H2O will appear before main ignition.

关键词：空气混合物煤油自燃特性点火延迟时间冲击管反应速率初始温度数据显示

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Thermodynamic, life cycle, and techno-economic assessment of an autothermal supercritical water gasification system for direct processing raw pig manure: Hydrogen generation and ammonia recovery

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Energy 2025年 330卷

作者： Mingming Du Fan Liu Haoran Yuan Yu-nan Chen Jing Gu Guangzhou Institute of Energy Conversion Chinese Academy of Sciences (CAS) Guangzhou 510640 PR China State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF) Xi'an Jiaotong University Xi'an Shaanxi 710049 PR China Guangdong Provincial Key Laboratory of Renewable Energy Guangzhou 510640 PR China

Supercritical water gasification (SCWG) exhibits an excellent potential for the conversion from pig manure (PM) to H 2 . However, the low solid content characteristic of raw PM and ammonia discharge significantly constrain the thermodynamic efficiency of SCWG. To address these limitations, a novel SCWG system was designed for simultaneous autothermal H 2 production and ammonia recovery from raw PM. Thermodynamic analysis, life cycle, and techno-economic were carried out to assess system performance. Results indicated that the novel system exhibited exceptional adaptability to variations in concentration and mass flow of raw PM, with autothermal H 2 production achieved even at low concentration of 10 %. Raw PM was converted into high-concentration slurries through pulping operations, thereby reducing exergy losses of gasification, heat exchange, and cooling units. Further, the system implemented an efficient ammonia recovery utilizing steam generated during the pulping stage. Under a typical scenario, energy efficiency, exergy efficiency, GWPs, and EP of the novel system reached 50.34 %, 45.99 %, 0.005 kgCO 2 -eq/kgH 2 , and 0.07 kgNO 3 - -eq/kg H 2 , respectively. The levelized hydrogen cost of the new system was 15.81 CNY/kg. This study provides a valuable solution for autothermal SCWG of low-solid-content and high-nitrogen-content feedstocks to produce H 2 and recover ammonia.

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MIXED DISCONTINUOUS GALERKIN METHOD FOR QUASI-NEWTONIAN STOKES flowS

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Journal of Computational Mathematics 2024年第3期42卷 885-910页

作者： Yanxia Qian Fei Wang Wenjing Yan School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China School of Mathematics and Statistics&State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,we introduce and analyze an augmented mixed discontinuous Galerkin(MDG)method for a class of quasi-Newtonian Stokes *** the mixed formulation,the unknowns are strain rate,stress and velocity,which are approximated by a discontinuous piecewise polynomial triplet ■for k≥***,the discontinuous piecewise polynomial function spaces for the field of strain rate and the stress field are designed to be *** addition,the pressure is easily recovered through simple *** the benefit of the analysis,we enrich the MDG scheme with the constitutive equation relating the stress and the strain rate,so that the well-posedness of the augmented formulation is obtained by a nonlinear functional *** k≥0,we get the optimal convergence order for the stress in broken ■(div)-norm and velocity in L^(2)-***,the error estimates of the strain rate and the stress in-norm,and the pressure in L^(2)-norm are optimal under certain ***,several numerical examples are given to show the performance of the augmented MDG method and verify the theoretical *** evidence is provided to show that the orders of convergence are sharp.

关键词： Quasi-Newtonian fows Mixed discontinuous Galerkin method Symmetric strain rate Symmetric stress Optimal convergence orders

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Effect of anolyte pH and cathode Pt loading on electricity and hydrogen co-production performance of the bio-electrochemical system

Effect of anolyte pH and cathode Pt loading on electricity a...

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作者： Liu, Ya-Peng Wang, Yun-Hai Wang, Bai-Shi Chen, Qing-Yun Department of Environmental Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In a novel bio-electrochemical system (BES) for hydrogen and electricity co-production with acetate substrate, the anolyte pH and cathode Pt loading effects are investigated to improve the cell performance for hydrogen and electricity co-production and reduce the cost. The optimized anolyte pH is 9. The maximum hydrogen production rate of 0.55 m3 m-3 d -1 and COD removal of 76% are obtained under optimal anolyte pH in the present BES. Over high or over low anolyte pH decreases the hydrogen production rate and COD removal. In addition, the experiments show that there is no considerable difference for the power density output and steady state current when the Pt catalyst loading is above 0.1 mg cm-2. But when the Pt catalyst loading is lower than 0.1 mg cm-2, the power density output and current decreases significantly. About 1.7 W m-3 power density output can be obtained by using 0.1 mg cm-2 Pt catalyst in the present research. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Hydrogen production

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