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Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor

Particuology 2016年第4期14卷 95-101页

作者： Xuedong Jiang Ning Yang Bolun Yang Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Center for Mesoscience and State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.

关键词： Computational fluid dynamics External loop airlift reactor Drag model Gas holdup Mnltiscale Mesoscale

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Gas and Liquid flow Rate Measurement in Wet Gas Based on Differential Pressure Signals

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Jixie Gongcheng Xuebao/Journal of Mechanical Engineering 2017年第24期53卷 55-62页

作者： Bai, Bofeng Zheng, Xuebo Qiu, Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Scientific Information Division Xinjiang Oilfield Company Karamay834000 China

The basic characteristics of differential pressure signals and the limitation of flow rate metering methods based on differential pressure are studied analytically and experimentally. Through the investigation into differential pressure signals of orifice plate and V-cone, it is found that the two-phase differential pressure is mainly caused by gas phase and is slightly affected by the liquid phase. In the case of low liquid hold up, the frictional pressure drop can be decreased due to the presence of the thin liquid film on the wall, resulting in that the two-phase differential pressure, pressure loss and pressure loss ratio decrease at first and then increase as the liquid hold up increases. The fluctuation of the differential pressure is stochastic, causing the fluctuation characteristic parameters, such as the standard deviation, having the properties of poor stability and repeatability. This makes it difficult to be applied to industrial wet gas metering. The error propagation analysis demonstrates that the prediction error of liquid phase flow rate is much larger than that of the gas phase, which is a universal phenomenon of metering methods based on over-reading correlations. Finally, we recommend that for wet gas with high gas void fraction, the liquid flow rate should be measured independently. The non-monotonicity of the pressure loss ratio needs to be concerned if it is chosen as the characteristic parameter. Parameters with poor repeatability, such as standard deviation, are not recommended for wet gas metering. © 2017 Journal of Mechanical Engineering.

关键词： flow rate

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Influence of Oxy-fuel Atmosphere on Microscopic Physical-Chemical Properties of High-alkali Ash at Softening Temperature

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Energy Procedia 2017年 142卷 3240-3243页

作者： Chang’an Wang Hanqing Li Chenzhao Zhu Tao Han Yinhe Liu Lei Deng Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The utilization of high-alkali coals in Zhundong coalfield with oxy-fuel combustion technology has a great potential, however, the ash fusion properties of high-alkali coals are still unclear. Here, we studied the influence of oxy-fuel atmosphere on the microscopic properties of high-sodium ash. The change from air to oxy-fuel condition has a negligible influence on ash fusion temperatures, but exhibits certain impact on physical-chemical properties of high-alkali ash. Oxygen content presents a primary effect on the microscopic morphology of ash at softening temperature.

关键词： high-alkali coal oxy-fuel combustion CO 2 capture microscopic properties SEM

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Investigation on Heat Transfer Characteristics of the H-type Finned Tube in Flue Gas with High Content of Ash

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Energy Procedia 2017年 105卷 4680-4684页

作者： Tao Han Chang’an Wang Qi Cao Wufeng Chen Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

H-type finned tube is rarely used in waste heat recovery power generation stations, though it has an efficient heat transfer performance in large thermal power stations (WHRPGs, hereafter). To date, understanding of heat performance of H-type finned tube in WHRPGs is still lacked. The heat transfer characteristics of H-type finned tube in gas with high content of ash in WHRPGs was investigated in practical cement plant in present work. The actual ash deposition pattern was observed meanwhile. The characteristics of heat transfer process including heat transfer coefficient, heat effective coefficient, and flue resistance at gas velocity between 4.5 - 6.5 m·s –1 are obtained. Experimental results show that the heat transfer coefficient increases with gas velocity linearly, the heat effective coefficient nearly keep stable on the other hand, and serious ash-block problem occurs in flow area in the heat exchanger at the gas velocity of 4.5 - 6.5 m·s –1 . The max heat transfer coefficient remain below 10 w·m –2 ·k –1 , implying heat performance of H-type finned tube in WHRPGs is possibly inefficient.

关键词： H-type finned tube heat performance heat transfer

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Insights into Charge Transfer at an Atomically Precise Nanocluster/Semiconductor Interface

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Angewandte Chemie 2020年第20期132卷

作者： Yu Wang Xiao‐He Liu Qiankun Wang Martin Quick Sergey A. Kovalenko Qing‐Yun Chen Norbert Koch Nicola Pinna Institut für Chemie and IRIS Adlershof Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany International Research Center for Renewable Energy (IRCRE) and State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China Institut für Physik and IRIS Adlershof Humboldt-Universität zu Berlin Brook-Taylor-Strasse 6 12489 Berlin Germany

The deposition of an atomically precise nanocluster, for example, Ag 44 (SR) 30 , onto a large‐band‐gap semiconductor such as TiO 2 allows a clear interface to be obtained to study charge transfer at the interface. Changing the light source from visible light to simulated sunlight led to a three orders of magnitude enhancement in the photocatalytic H 2 generation, with the H 2 production rate reaching 7.4 mmol h −1 g catalyst −1 . This is five times higher than that of TiO 2 modified with Ag nanoparticles and even comparable to that of TiO 2 modified with Pt nanoparticles under similar conditions. Energy band alignment and transient absorption spectroscopy reveal that the role of the metal clusters is different from that of both organometallic complexes and plasmonic nanoparticles: A type II heterojunction charge‐transfer route is achieved under UV/Vis irradiation, with the cluster serving as a small‐band‐gap semiconductor. This results in the clusters acting as co‐catalysts rather than merely photosensitizers.

关键词： Ladungstransfer Cokatalysatoren Photosensibilisator Silber-Nanocluster

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Black TiO_(2) for solar hydrogen conversion

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Journal of Materiomics 2017年第2期3卷 96-111页

作者： Bin Wang Shaohua Shen Samuel S.Mao School of Science MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed MatterState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityShaanxi710049China Xi'an Jiaotong University Suzhou Academy SuzhouJiangsu215123China Department of Mechanical Engineering University of California at BerkeleyBerkeleyCA94720United States Samuel Mao Institute of New Energy Science Hall1003 Shangbu RoadShenzhen518031China

Titanium dioxide(TiO_(2))has been widely investigated for photocatalytic H_(2) evolution and photoelectrochemical(PEC)water splitting since ***,its wide bandgap(3.0-3.2 eV)limits the optical absorption of TiO_(2) for sufficient utilization of solar *** TiO_(2) has been proposed as an effective strategy to enhance its solar absorption and thus the photocatalytic and PEC activities,and aroused widespread research *** this article,we reviewed the recent progress of black TiO_(2) for photocatalytic H_(2) evolution and PEC water splitting,along with detailed introduction to its unique structural features,optical property,charge carrier transfer property and related theoretical *** summarized in this review article,black TiO_(2) could be a promising candidate for photoelectrocatalytic hydrogen generation via water splitting,and continuous efforts are deserved for improving its solar hydrogen efficiency.

关键词： Black TiO_(2) Photoelectrochemical water splitting Photocatalytic Hydrogen evolution

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Three-dimensional analysis of condensation nanofluid film on an inclined rotating disk by efficient analytical methods

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Arab Journal of Basic and Applied Sciences 2018年第1期25卷 28-37页

作者： Hatami, M. Jing, D. Yousif, Majeed A. Department of Mechanical Engineering Esfarayen University of Technology Esfarayen Iran State Key Laboratory of Multiphase Flow in Power Engineering & International Research Center for Renewable Energy Xi’an Jiaotong University Xi’an China Department of Mathematics Faculty of Science University of Zakho Zakho Iraq

In this study, least square method (LSM) and differential transform method (DTM) applied to solve the three dimensional problem of steady nanofluid deposition on an inclined rotating disk is illustrated. The governing non-linear partial differential equations are reduced to the nonlinear ordinary differential equations system by similarity transform. There is a good agreement between the present analytical and numerical results. Results indicate that increasing nanofluid volume fraction leads to increase in temperature profile and highest temperature obtained for aluminium oxide (Al₂O₃)-water case. © 2018, © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of the University of Bahrain.

关键词： condensation film DTM film thickness LSM Nanofluid rotating disk

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Lithium–Sulfur Batteries: Flexible and High‐Loading Lithium–Sulfur Batteries Enabled by Integrated Three‐In‐One Fibrous Membranes (Adv. Energy Mater. 38/2019)

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Advanced Energy Materials 2019年第38期9卷

作者： Jianan Wang Guorui Yang Jie Chen Yunpeng Liu Yuankun Wang Cheng‐Yen Lao Kai Xi Duowen Yang Christopher J. Harris Wei Yan Shujiang Ding Ramachandran Vasant Kumar Department of Applied Chemistry School of Science MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter State Key Laboratory for Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an 710049 China Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Materials Science and Metallurgy University of Cambridge Cambridge CB3 0FS UK

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Effect of prompt dissociation of formyl radicals on 1,3,5-trioxane laminar flame speeds at high pressure 55

Effect of prompt dissociation of formyl radicals on 1,3,5-tr...

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55th AIAA Aerospace Sciences Meeting

作者： Zhao, Hao Fu, Jiapeng Ju, Yiguang Department of Mechanical and Aerospace Engineering Princeton University Engineering Quad Olden Street PrincetonNJ08544 United States Department of Power Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

ISBN: (纸本)9781624104473

Flame speeds of all hydrocarbon fuels are very sensitive to the reactions of formaldehyde (CH2O) and formyl radical (HCO). In this paper, we studied the prompt dissociation effect of HCO on the flame speeds of trioxane and formaldehyde up to 9 atm. The effects of prompt HCO dissociation were examined at high pressure. Different kinetic models were compared against the experimental results. The results showed there was a significant effect of the HCO prompt reaction on the flame speed in a broad range of pressure and equivalence ratio. At higher pressure, it was observed that the prompt effect was reduced due to the third-body collision effect. However, with the increase of O2mole fraction, the prompt effect was enhanced. Comparison showed that HP Mech with the inclusion of the prompt reactions had a better prediction at lean and ultra-lean conditions than other mechanisms. The improved prediction of the flame speed indicated that the prompt effect needed to be considered in the model development of hydrocarbon and oxygenated fuel combustion. © 2017 by Hao Zhao, Jiapeng Fu, and Yiguang Ju.

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Multi-objective optimization of a printed circuit heat exchanger design 17

Multi-objective optimization of a printed circuit heat excha...

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17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017

作者： Wang, L. Chen, M. Shi, S. Che, D. Sun, X. Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd. Ann ArborMI48109-2104 United States State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi710049 China

Due to their high effectiveness and compact size, printed circuit heat exchangers (PCHEs) appear promising to be employed as intermediate heat exchangers (IHXs) in High-Temperature Gas-cooled Reactors (HTGRs). In the literature, PCHEs of zigzag mini-channel designs have demonstrated superior performance in heat transfer and pressure drop. In this research, a three-dimensional numerical simulation was performed for a PCHE using computational fluid dynamics (CFD) tool ANSYS FLUENT to study the effects of the zigzag pitch and angle, and channel diameter on its thermal-hydraulic performance. The mass, momentum, and energy equations were solved using a finite volume method by considering steady-state, incompressible laminar flow. The FLUENT numerical model was validated by comparing the simulation results with the experimental data obtained in a high-temperature helium test facility. The comparison showed overall good agreement between the simulations and experiments. In addition, it was challenging to obtain accurate correlations/models for the Nusselt number and friction factor with various geometrical and operational parameters considered. In our study, two artificial neural network (ANN) models were applied by utilizing the CFD results to predict the Nusselt number and friction factor in PCHE zigzag channels with different geometrical configurations and operational parameters. Consequently, the computation time needed for the PCHE design optimization process could be significantly reduced. The comparison between the ANN predictions and CFD results showed that the ANN models could predict the numerical data with good accuracies. Furthermore, to achieve an optimal heat exchanger design, two conflicting evaluation criteria were proposed based on the capital and operational costs. Finally, the Non-dominated Sorting Genetic Algorithms (NSGA-II) and the proposed ANN models were combined and utilized to optimize the geometrical design parameters of the zigzag-channel PCHEs.

关键词： Multiobjective optimization

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