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15th International Heat Transfer Conference, IHTC 2014

作者： Lei, Yuan Zhang, Baowen Bai, Bofeng Zhao, Tianshou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 28 Xianning West Rd. Beilin District Xi'an710049 China Department of Mechanical Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

Membrane, as a key component in all-vanadium redox flow batteries, plays the role of conducting the current and isolating the solutions between the anode and cathode electrodes. Both functional groups and charge numbers of membranes influence the performance of the battery. However, in simulating the species crossover through the membrane conventional models take account of mass transfer with the effect of functional groups in the membrane on crossover neglected. In this work, we propose an 1-D model for the membrane region of all-vanadium redox flow battery with the effect of functional groups considered. The model is formulated based on the conservation equations for charge and mass. Donnan potentials at the interfacial regions between membrane and electrodes are modeled, where the conditions are non-electrically neutral. The effects of various factors, including the state of charge, the number of functional groups and the applied current on species crossover are studied. It is shown that there exists a significant jump in electric potential and ion concentrations at the interfacial regions between membrane and electrodes. For a cation membrane, the concentrations of cations at the membrane side in the interfacial region are higher than those at the electrode side, while those of anions opposite. With more charges in the cation exchange membrane, the fluxes of vanadium ions crossover through the membrane are larger, leading to a lower efficiency. The model not only helps shed light into the mechanism of species crossover through the membrane, but also provides a tool to optimize the membrane design for all-vanadium flow batteries.

关键词： Membranes

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Numerical simulation of hemodynamics in portal vein with thrombosis by computational fluid dynamics

Numerical simulation of hemodynamics in portal vein with thr...

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作者： Wang, Xinkai Li, Guojie Chen, Bin Pu, Yansong Nie, Peng Li, Xiao Li, Zongfang Su, Kai State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China Department of General Surgery Second Affiliated Hospital Xi'An Jiaotong University Xi'an710004 China Huaihe Hospital of Henan University Kaifeng475000 China

Portal vein thrombosis (PVT) is an important complication that is associated with cirrhotic portal hypertension. The etiology is as yet unclear but could be closely related to the hemodynamics of the portal vein system. This paper investigated the hemodynamics in the portal vein model, both with and without thrombosis, as well as the effect of obstructions on the hemodynamics of the portal vein system using the computational fluid dynamics (CFD) method. PVT can probably develop in the inlets of the portal vein as well as the left/right branches of the portal vein because the distribution of wall shear stress satisfies the conditions for PVT formation based upon the simulation of the hemodynamics in the normal portal vein model. According to the above results, geometric models for a portal vein with a thrombus were constructed and the influence of different degrees (26%, 39%, 53% and 64%) of obstructions was studied. In the model with the maximum obstruction (64% blocked), the maximum velocity of portal vein (PV) increased up to twice than in the model without thrombosis, and the maximum wall shear stress of PV in the model with thrombosis (64% blocked) increased up to 9.4 Pa, whereas it was only 1.9 Pa in the model without thrombosis (nearly one fifth of the maximum wall shear stress). Excessive wall shear stress may cause mechanical damage to the blood vessels and induce physiological changes. © 2014 World Scientific Publishing Company.

关键词： Computational fluid dynamics

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Novel doped barium cerate-carbonate composite electrolyte material for low temperature solid oxide fuel cells

Novel doped barium cerate-carbonate composite electrolyte ma...

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作者： Hei, Yuanfei Huang, Jianbing Wang, Cheng Mao, Zongqiang International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xianning West Road No. 28 Xi'an 710049 China Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China

A composite of a perovskite oxide proton conductor (BaCe 0.7Zr0.1Y0.2O3-δ, BCZ10Y20) and alkali carbonates (2Li2CO3:1Na2CO 3, LNC) is investigated with respect to its morphology, conductivity and fuel cell performance. The morphology shows that the presence of carbonate phase improves the densification of oxide matrix. The conductivity is measured by AC impedance in air, nitrogen, wet nitrogen, hydrogen, and wet hydrogen, respectively. A sharp increase of the conductivity at certain temperature is seen, which relates to the superionic phase transition at the interface phases between oxide and carbonates. Single cell with the composite electrolyte is fabricated by dry-pressing technique, using nickel oxide as anode and lithiated nickel oxide as cathode, respectively. The cell shows a maximum power density of 957 mW cm-2 at 600 °C with hydrogen as the fuel and oxygen as the oxidant. The remarkable proton conductivity and excellent cell performance make this kind of composite material a good candidate electrolyte for low temperature solid oxide fuel cells (SOFCs). © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Nickel oxide

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Characterization of biogas-hydrogen premixed flames using Bunsen burner

Characterization of biogas-hydrogen premixed flames using Bu...

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作者： Zhen, H.S. Leung, C.W. Cheung, C.S. Huang, Z.H. Department of Mechanical Engineering Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong State Key Laboratory of Multiphase Flows in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Experimental study is conducted to clarify the effects of hydrogen addition to biogas and hydrogen fraction in the biogas-H2 mixture on the stability, thermal and emission characteristics of biogas-H2-air premixed flames using a 9 mm-ID-tube Bunsen burner. Variation in biogas composition is allowed to range from BG60 (60%CH4- 40%CO2), down to BG50 (50%CH4-50%CO 2) and to BG40 (40%CH4-60%CO2). For each biogas, the fraction of hydrogen in the biogas-H2 mixture is varied from 10% to 50%. The results show that upon hydrogen addition and increasing hydrogen fraction in the fuel mixture, there are corresponding changes in flame stability, laminar burning velocity, flame tip temperature and CO pollutant emission. Under the tested conditions of 400 ≤ Re ≤ 800 and 0.8 ≤ φ ≤ 1.2, the otherwise incombustible biogas-air mixture becomes flammable upon hydrogen addition and the threshold value of hydrogen fraction for occurrence of stable flames increases with the increase in the CO concentration of biogas. Overall, the flame stability is best at rich equivalence ratio of φ = 1.2. The laminar burning velocity of the biogas-H2-air mixture is found to be higher than pure biogas due to addition of hydrogen, and it monotonically increases at higher hydrogen fraction. Further, a shift in equivalence ratio for peak laminar burning velocity from stoichiometric ≤ = 1.0 to φ = 1.2 is observed. The results also show a monotonic increase in flame temperature and a monotonic decrease in CO emission at higher hydrogen fraction. The more efficient oxidation of CO into CO2 reveals that more complete combustion is induced by hydrogen addition. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Velocity

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Three-dimensional steady calculation on two-phase flow in secondary side of steam generator

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Hedongli Gongcheng/Nuclear power engineering 2014年第2期35卷 37-40页

作者： Cong, Tenglong Tian, Wenxi Qiu, Suizheng Su, Guanghui Xie, Yongcheng Yao, Yangui Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Shanghai Nuclear Engineering Research and Design Institute Shanghai 200233 China

Secondary side two-phase flow in steam generator was simulated based on the porous media model. Additional momentum and energy source terms were appended to the momentum and energy equations of porous media region, respectively. The additional momentum source contained the resistances of downcomer, tube bundle, support plate and separator. The additional energy source included the heat transfer from primary side to secondary side fluid. Solving the control equations by ANSYS FLUENT solvers yielded the distributions of velocity, temperature, pressure, density and quality. The distributions of velocity, void fraction and mixture density in hot side vary significantly from these in cold side;the void fraction at the inlet of separator differs from 0.63 to 0.98;pressure descends along axial direction, while at the positions of support plates, pressure declines sharply.

关键词： Porous materials

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Tandem cylinder flow and noise control 20

Tandem cylinder flow and noise control

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20th AIAA/CEAS Aeroacoustics Conference 2014

作者： Liu, Hanru Azarpeyvand, Mahdi Wei, Jinjia Ilário da Silva, Carlos R. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Mechanical Engineering Department University of Bristol BS8 1TR United Kingdom EMBRAER S.A. São José dos Campos São Paulo Brazil

ISBN: (数字)9781624102851

ISBN: (纸本)9781624102851

This paper is concerned with the application of porous coatings as a passive flow control method for reducing the aerodynamic sound from cylinders in tandem. The aim here is to perform a parametric proof-of-concept study to investigate the effectiveness of porous treatment on bare tandem cylinders to control and regularize the vortex shedding and flow within the gap region between the two bluff bodies, and thereby control the aerodynamic sound generation mechanism. The aerodynamic simulations are performed using 2D transient RANS approach with k-ω transitional turbulence model and the acoustic computations are carried out using the standard Ffowcs Williams-Hawkings (FW-H) acoustic analogy. Numerical flow and acoustic results are presented for bare tandem cylinders and porous-covered cylinders, with different porosities and thicknesses. Experimental flow and acoustic data are also provided for comparison. Results show that the proper use of porous coatings can lead to robust control of the flow within the gap region, the turbulence level and interaction with the downstream body, and therefore the generation of tonal and broadband noise. It has also been observed that the magnitude and the frequency of the primary tone reduce significantly as a result of the flow regularization. Preliminary experimental results are also provided for a single cylinder, confirming that the use of porous covers can effectively control the lift fluctuation near the primary vortex shedding tone.

关键词： Vortex shedding

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Analysis of the loss of pool cooling accident in a PWR spent fuel pool with MAAP5

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Annals of Nuclear Energy 2014年 72卷 198-213页

作者： Xiaoli Wu Wei Li Yapei Zhang Wenxi Tian Guanghui Su Suizheng Qiu State Key Laboratory of Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi’an Jiaotong University No. 28 Xianning West Road Xi’an Shanxi 710049 China

The Fukushima Daiichi nuclear accident shows that it is necessary to study potential severe accidents and corresponding mitigation measures for the spent fuel pool (SFP) of a nuclear power plant (NPP). This paper presents the analysis of loss of pool cooling accident scenarios and the discussion of mitigation measures for the SFP at a pressurized water reactor (PWR) NPP with the MAAP5 code. Analysis of uncompensated loss of water due to the loss of pool cooling with different initial pool water levels of 12.2 m (designated as a reference case) and 10.7 m have been performed based on a MAAP5 input model. Scenarios of the accident such as overheating of uncovered fuel assemblies, oxidation of claddings and hydrogen generation, loss of intactness of fuel rod claddings, and release of radioactive fission products were predicted with the assumption that mitigation measures were unavailable. The results covered a broad spectrum of severe accident evaluations in the SFP. Furthermore, as important mitigation measures, the effects of recovering the SFP cooling system and makeup water in SFP on the accident progressions have also been investigated respectively based on the events of pool water boiling and spent fuels uncovery. Based upon the reference case, three cases with the recovery of SFP cooling system and three other cases with makeup water in SFP have been studied. The results showed that, severe accident might happen if SFP cooling system was not restored timely before the spent fuels started to become uncovered; spent fuels could be completely submerged and severe accident might be avoided if SFP makeup water system provided water with a mass flow rate larger than the average evaporation rate defined as the division of pool water mass above the top of the spent fuel assemblies by the amount of time to start uncovering the spent fuel assemblies when no mitigation measures were taken. Although spent fuel assemblies were partly exposed due to the mass flow rate of

关键词： Spent fuel pool MAAP5 Loss of pool cooling accident Mitigation measures

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A-Novel-CdS-Nanorod with Stacking Fault Structures: Preparation and Properties of Visible-Light-Driven Photocatalytic Hydrogen Production from Water Splitting

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Energy Procedia 2014年 61卷 2450-2455页

作者： Kai He Liejin Guo International Research Centre for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi 710049 China (Kai He will present the paper at the conference)

In the present study, CdS nanorod particles with the stacking fault structures were hydrothermally synthesized through a dissolution-recrystallization approach in concentrated ammonia solvent, for the first time. It was clear that concentrated ammonia solution contained a large number of hydroxyl ions and large numbers of ammonia. Comprehensive characteristics were performed to investigate the influence of stacking fault structures on the photocatalytic activity and stability of CdS nanorod particles. Transmission electron microscopy (TEM) images revealed that the CdS catalyst included many nanorods with stacking fault structures. Stacking fault structures were obviously observed within CdS nanorods with the length ranging from 70 to 200 nm and diameter ranging from 20 to 65 nm, respectively. It revealed that the formation of CdS nanorod particles with stacking faults was contributed to the dissolution-recrystallization process. There were many structural units for cubic phase changing to hexagonal phase in the CdS crystals in the process of hydrothermal resulting in forming a large number of stacking fault structures. Photo-generated electrons and holes migrating directionally along the nanorods direction and the stacking fault structures in some nanorods could promote the separation of photo-generated electrons and holes, which enhanced the activity of visible-light-driven photocatalytic hydrogen production. Through the photocatalytic hydrogen production experiments, CdS nanorod particles with the stacking fault structures showed much higher photocatalytic activity than CdS patticles prepared by the conventional hydrothermal method using the water as the hydrothermal solvent.

关键词： CdS Nanorods Stacking fault structures Photocatalytic hydrogen production

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FUNCTIONALIZED MODIFICATION TO G-C3N4 FOR EFFICIENT PHOTOCATALYTIC HYDROGEN GENERATION: ENHANCED OPTICAL ABSORPTION AND PROMOTED CHARGE SEPARATION

FUNCTIONALIZED MODIFICATION TO G-C3N4 FOR EFFICIENT PHOTOCAT...

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10th IUPAC International Conference on Novel Materials and their Synthesis NMS-X(IUPAC第十届新材料及其合成国际会议)

作者： S.SHEN J.CHEN International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi''an Jiaotong UniversityShaanxi 710049China

Metal oxide or metal nanodots modified g-C_3N_4 was fabricated using a facile evaporation-annealing method. The effect of metal oxide or metal nanodots decoration on the rate of visible-light (λ ＞ 420 nm) photocatalytic activity was studied by hydrogen production from triethanolamine (TEOA) aqueous solutions. The highest photocatalytic activity was observed on Cu(0.05wt%)/g-C_3N_4 with the hydrogen evolution rate of 241.3 μmolh~(-1)g~(-1), which exceeded that of pure g-C_3N_4 (141.6 μmolh~(-1) g~(-1) ) by more than 70%. The mechanism for the enhanced visible-light photocatalytic activity of g-C_3N_4 decorated with metal oxide or metal nanodots was carefully investigated. For the metal oxide nanodots decorated g-C_3N_4, the improved photocatalytic activity could be contributed to the promoted charge carrier transfer ability, as revealed by time-resolved photoluminescence emission decay spectra; for the metal nanodots decorated g-C_3N_4 (e.g. Ag@SiO_2/g-C_3N_4), the enhanced visible light absorption induced by plasmon effect greatly contributed to the improved photocatalytic activity for hydrogen production.

关键词： g-C3N4 optical absorption charge separation

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Study on ignition delay of multi-component syngas using shock tube

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Canadian Journal of Chemical engineering 2014年第5期92卷 861-870页

作者： Thi, Luong Dinh Zhang, Yingjia Fu, Jin Huang, Zuohua Zhang, Yang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Combustion and Flow Diagnostics Research Group Department of Mechanical Engineering University of Sheffield Sheffield S1 3JD United Kingdom

Ignition delays of four typical syngas mixtures were investigated using both experimental and simulated methods. The shock tube experiments were conducted behind the reflected shock waves at temperature ranges from 870 to 1350K, pressures of 0.2, 1.0 and 2.0MPa. Six available kinetic models were evaluated by comparing them to the new ignition delay data obtained. NUIG C3 model was in good agreement with the experimental results. The effect of the pressure on ignition delay of all four syngas mixtures was similar to that of hydrogen. The promoting and inhibiting ignition were experimentally observed at high and moderate temperatures, respectively. Sensitivity analyses were conducted at different temperatures and pressures to identify the dominant elementary reactions in the ignition process of the syngas. The results indicated that the ignition delay was generally most sensitive to the chain branching reaction H+O2=O+OH at both high and low temperatures. Decomposition reaction H2O(+M)=H+OH (+M) was of importance for the syngas with relative inert gas CO2 and N2 at a high temperature. The reaction CO+OH=CO2+H involving CO kinetic dominated the ignition at a high temperature for the syngas with a high CO level. The inhibiting effect of pressure was attributed to the decrease of sensitivity of the reactions H+O2=O+OH and O+H2=H+OH and the increase of sensitivity of the reaction H+O2 (+M)=HO2(+M) at a moderate-low temperature. © 2013 Canadian Society for Chemical engineering.

关键词： Carbon dioxide

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