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Viscosity Measurements of n-Dodecane at Temperatures between 303 K and 693 K and Pressures up to 10 MPa

JOURNAL OF CHEMICAL AND engineering DATA 2018年第3期63卷 671-678页

作者： Feng, Song Liu, Zhaohui Bi, Qincheng Pan, Hui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The dynamic viscosities of n-dodecane were measured at temperatures between 303.3 and 693.3 K and pressures up to 10.0 MPa using a dual-capillary viscometer. The accuracy of the dual-capillary viscometer was improved by considering centrifugal effects and the thermal expansion of the capillary. The combined relative standard uncertainty in the dynamic viscosity was calculated to be 0.58-2.92 %. This study provides new data to check the accuracy of Huber's correlations at supercritical pressures, and a small proportion of the data points at supercritical conditions where few experimental data have been reported. The average absolute deviation between the experimental data and the calculated data from Huber's correlations is 0.97%, and the maximum absolute deviation is 6.79%. In the near-critical and supercritical region, the accuracy of viscosities of n-dodecane needs more experimental data for verification and to extend the theories.

关键词： Hydrocarbons Theoretical and computational chemistry Mixtures Viscosity Fuels

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Study on the natural frequencies of pipes conveying gas-liquid two-phase slug flow

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2018年 141卷 168-188页

作者： Liu, Gang Wang, Yueshe Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The natural frequencies of pipes conveying gas-liquid two-phase slug flow are explored, considering the significance of the intermittent characteristic of gas-liquid two-phase slug flow particularly. The widely used finite element method is employed to establish the theoretical model. The local flow parameters including local gas and liquid velocities and local liquid holdup varying with time and position along the pipe are calculated to obtain the global matrix equation of motion for the system. An experiment is conducted to verify the theoretical model. The results show that the time domain values of the natural frequency would keep periodicity during the process of slug flow. Root-mean-square of the natural frequency is employed to represent the characteristic of the piping system natural frequency. If the superficial gas velocity is given, root-mean-square of the natural frequency will decrease with the increase of the superficial liquid velocity. Yet if the superficial liquid velocity is given, root-mean-square of the natural frequency will increase firstly and then decrease with the increase of superficial gas velocity when the superficial liquid velocity is relatively large. Thus a critical superficial gas velocity exists for these conditions. The range of superficial gas velocity that could make the system become unstable may be predicted preliminarily by analyzing this critical value. Sufficient analysis of slug parameters and geometrical parameters of the pipes is necessary to obtain the critical superficial gas velocity. Finally, the divergent instability of the piping system is predicted based on the above analysis.

关键词： Two-phase slug flow Intermittent Finite element method Natural frequency

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Transition-metal alloy electrocatalysts with active sites modulated by metal-carbide heterophases for efficient oxygen evolution

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NANO ENERGY 2021年 88卷 106216-106216页

作者： Wang, Miao Wang, Yiqing Mao, Samuel S. Shen, Shaohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Int Res Ctr Renewable Energy Xian 710049 Shaanxi Peoples R China Samuel Mao Inst New Energy Guangzhou 518031 Guangdong Peoples R China Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA Khalifa Univ Sci & Technol Masdar Inst Abu Dhabi 127788 U Arab Emirates

Given oxygen evolution reaction as the rate-limiting step for electrocatalytic water splitting, it is essential to accelerate water oxidation kinetics by modulating the population and intrinsic activity of active sites. Herein, by annealing the mixture of Fe, Ni, and Mo precursors, FeNi alloys compositing with Mo2C heterophases supported on carbon layers (FeNi-Mo2C/C) were synthesized and exhibited a promising activity for oxygen evolution, with a small overpotential of 288 mV at 10 mA cm-2, which is even superior to the benchmark noble metal-based catalyst (e.g., RuO2). The introduced Mo2C heterophases reduced the particle size of FeNi alloys, increasing the amount of surface electrocatalytically active sites, and tuned the electronic structures of FeNi alloys, stimulating the surface phase transformation with highly-active metal oxides formed for the enhanced intrinsic activity of active sites. This work presents an effective and alternative approach to the modulation of electrocatalytic active sites for electrochemical energy applications.

关键词： Water splitting Electrocatalytic oxygen evolution Heterophase Active sites Intrinsic activity

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Hydrogen production by biomass gasification in a supercritical water fluidized bed reactor: A CFD-DEM study

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JOURNAL OF SUPERCRITICAL FLUIDS 2018年 131卷 26-36页

作者： Zhao, Lixing Lu, Youjun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

In this study, we used CFD-DEM model to simulate glucose gasification in a supercritical water fluidized bed reactor (SCWFBR). Simplified reaction kinetic model, including glucose decomposition, water gas shift reaction and methanation reaction, was used. Particle distributions, gas composition and reaction rate profiles were analyzed. Moreover, the influence of chemical reaction on flow behavior, and the effects of operation parameters, such as wall temperature, flow rates and initial bed height were investigated. The results show that high wall temperature, low flow rate and high initial bed height are in favor of gasification. However, lower H-2 yield, gasification efficiency (GE) are found at flow rate below the minimum fluidization velocity. The simulation results show good agreement with the experimental results, demonstrating the validity of this model. The information obtained by the numerical study is useful for the. operation and optimization of the gasification reactor.

关键词： Supercritical water Fluidized bed reactor Biomass gasification CFD-DEM

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Experimental Investigation on Enhanced Oil Recovery of Extra Heavy Oil by Supercritical Water Flooding

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ENERGY & FUELS 2018年第2期32卷 1685-1692页

作者： Zhao, Qiuyang Guo, Liejin Huang, Zujie Chen, Lei Jin, Hui Wang, Yechun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Exploitation of deep extra heavy oil is a challenging work due to its high viscosity and high reservoir pressure. Supercritical water is first proposed as an injection agent, considering its favorable physiochemical properties. A novel flooding experimental system with a design temperature up to 450 degrees C and pressure up to 30 MPa was developed to demonstrate the feasibility of supercritical water flooding (SCWF) technology. A sand pack core with an adiabatic boundary was used to eliminate heat unbalance. The experimental results indicated that SCWF is a promising enhanced oil recovery technology. SCWF could significantly enhance oil recovery when compared with steam flooding and hot water flooding and reduce the oil viscosity simultaneously. SCWF at 25 MPa and 400 degrees C raised the recovery efficiency to 97.07% and reduced oil viscosity by 36.9%. The mechanism is attributed to the extraction heavy oil components into the water-rich phase by supercritical water and the formation of miscible flooding.

关键词： Enhanced oil recovery supercritical water Oil recovery heavy oil Flood oil viscosity RECOVERY EFFICIENCY MISCIBLE DRIVE design temperature

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POOL BOILING EXPERIMENT ON A MODIFIED MICROPIN-FINNED SURFACE WITH MECHANICAL OSCILLATION

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HEAT TRANSFER RESEARCH 2018年第11期49卷 991-1001页

作者： Wei, Jinjia Kong, Xin Ding, Jie Zhang, Yonghai Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

To further enhance pool boiling heat transfer, a new oscillation device was proposed. An oscillating plate was located over the heater surface with a vertical oscillation amplitude of 20 mm and frequency of 6 Hz. Three N-type phosphorus-doped silicon chips were used as heater surfaces. One was a smooth surface, and the other two were micropin-finned chips with a fin side length of 30 mu m and fin height of 60 mu m (chip PF30-60), and the pin fins were arrayed with aligned and staggered arrangements, respectively. Absolute ethyl alcohol was used as a working fluid. The results showed that mechanical oscillation can enhance boiling heat transfer in both convective region and high heat flux region. The wall superheat showed a considerable decrease of 20-30 degrees C in the convective region by thinning the thermal boundary layer on the heater surface, and the critical heat flux could also be increased by 20%. In addition, the micropin-finned chips showed better performance due to much more fresh liquid supply from the interconnected tunnels formed by micropin fins, which is driven by capillary force.

关键词： micropin fin oscillation boiling heat transfer

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Investigation of the fuel effects on burning velocity and flame structure of turbulent premixed flames based on leading points concept

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COMBUSTION SCIENCE AND TECHNOLOGY 2018年第8期190卷 1354-1376页

作者： Zhang, Weijie Wang, Jinhua Yu, Qianqian Jin, Wu Zhang, Meng Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The measurements on flame structure and burning velocities of C3H8/air, CH4/air and CO/H-2/air turbulent premixed flames were conducted. Various experimental conditions for these mixtures were considered to understand the molecular and thermal diffusion process in turbulent flame, which was referred to the fuel effects. The fuel effects are interpreted as local burning velocity variation caused by molecular and thermal diffusivity with stretch effect. Leading points concept is a promising scaling approach to incorporate the fuel effects in turbulent flames recently. In this article, data across a variety of equivalence ratio and hydrogen fractions were obtained using Bunsen burner. Flame front was detected with OH-PLIF technique and turbulent burning velocity S-T referred to leading edge was derived. A new leading points characteristic speed S-L,S-LP was presented invoking both negative and positive Markstein number mixtures, revising the previous model in literature which is only suitable for negative Markstein number fuels. The turbulent burning velocity S-T under relatively weak turbulence intensity in this study and data of high turbulence intensity, high pressure from literature were renormalized with S-L,S-LP instead of S-L,S-0 based on leading points concept, where S-L,S-0 is the unstretched laminar flame speed. The results show that all the data sets were collapsed well which validated the significance of S-L,S-LP in normalizing S-T of different mixtures. An empirical formula for turbulent burning velocity correlation was obtained as. This formula is similar to that of Kobayashi;however, it shows superiority in incorporating the fuel effects.

关键词： Turbulent burning velocity turbulent premixed flame leading points concept fuel effects

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Characteristics of bubble, cloud and wake in jetting fluidised bed determined using a capacitance probe

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CHEMICAL engineering RESEARCH & DESIGN 2018年 136卷 687-697页

作者： Huang, Jikai Lu, Youjun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Detailed properties of bubble, cloud and wake in a jetting fluidised bed are studied by a capacitance probe method in this paper. In a jetting fluidized bed, when smaller particles are fluidised, bubble size and rising velocity initially increase near the distributer and maintains almost constant values with the increase in bed height. When bigger particles are fluidized, the bubble size and rising velocity decreased with the increase in bed height. The bubbles in bed when bigger particles are fluidised are smaller than those when smaller particles are fluidised under the same operating conditions. Background gas velocity has a more significant influence on bubble size, whereas the jetting gas velocity has a more significant influence on bubble rising velocity. The effect of operating conditions and bubble size on the averaged voidage of cloud or wake is negligible. Besides, the thickness of cloud and wake increases with bubble size, and the thickness of cloud is greater than that of wake. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Jetting fluidized bed Bubble dynamics Cloud and wake Capacitance probe

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Significantly enhanced electrostatic energy storage performance of P (VDF-HFP)/BaTiO3-Bi(Li0.5Nb0.5)O3 nanocomposites

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NANO ENERGY 2020年 78卷

作者： Wang, Peng-Jian Zhou, Di Li, Jing Pang, Li-Xia Liu, Wen-Feng Su, Jin-Zhan Singh, Charanjeet Trukhanov, Sergei Trukhanov, Alex Xi An Jiao Tong Univ Elect Mat Res Lab & Multifunct Mat & Struct Key Lab Minist Educ Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Int Ctr Dielect Res Sch Elect Sci & Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment Xian 710049 Shaanxi Peoples R China Xian Technol Univ Microoptoelect Syst Labs Xian 710032 Shaanxi Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Lovely Profess Univ Sch Elect & Commun Engn Jalandhar Punjab India Natl Univ Sci & Technol MISiS Leninskii Av 4 Moscow 4119049 Russia South Ural State Univ Lenin Av 76 Chelyabinsk 454080 Russia NAS Belarus Sci & Pract Mat Res Ctr P Brovki Str 19 Minsk 220072 BELARUS

Microelectronics and electrical power systems require dielectric polymer-based dielectrics with high energy density that are simple to process. However, the currently available polymer-based dielectric materials require demanding process conditions and relatively low energy density. Herein, we propose P(VDF-HFP)-based nano composite by a simple and practical mechanical method based on a combination of solid phase reaction and sieving to prepare 0.88BaTiO(3)-0.12Bi(Li0.5Nb0.5)O-3 nanoparticles (BT-BLN nps). The experimental and simulation result verify that the BT-BLN nps significantly improve the breakdown strength and energy storage performance of dielectric materials. Remarkably, the highest discharge energy density of the BT-BLN/P(VDF-HFP) nanocomposite film reached 14.2 J/cm(3) with the addition of 3 vol% BT-BLN nanofiller at 497 MV/m, which is much higher than that of pure P(VDFHFP) (Ud approximate to 6.6 J/cm(3) and Eb approximate to 391.3 MV/m). Encouragingly, the Young's modulus of BLN-3vol%/P(VDF-HFP) reached 2.6 GPa, which is approximately 2.65 times higher than that of pure P(VDF-HFP) (0.98 GPa). This work established a simple and effective strategy, for solution casting processable dielectrics with performance comparable to that of fillers prepared by the liquid phase method.

关键词： Nanocomposite BaTiO3-Bi(Li0.5Nb0.5)O-3 Breakdown strength Energy storage

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Ultrahigh enhancement rate of the energy density of flexible polymer nanocomposites using core-shell BaTiO3@MgO structures as the filler

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JOURNAL OF MATERIALS CHEMISTRY A 2020年第22期8卷 11124-11132页

作者： Wang, Peng-Jian Zhou, Di Guo, Huan-Huan Liu, Wen-Feng Su, Jin-Zhan Fu, Mao-Sen Singh, Charanjeet Trukhanov, Sergei Trukhanov, Alex Xi An Jiao Tong Univ Sch Elect Sci & Engn Elect Mat Res LabMinist Educ Multifunct Mat & StructKey LabInt Ctr Dielect R Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Northwestern Polytech Univ Sch Mat Sci & Engn Shaanxi Mat Anal & Res Ctr Xian 710072 Shaanxi Peoples R China Lovely Profess Univ Sch Elect & Commun Engn Jalandhar Punjab India Natl Univ Sci & Technol MISiS Leninskii Ave 4 Moscow 4119049 Russia South Ural State Univ Lenin Ave 76 Chelyabinsk 454080 Russia NAS Belarus Sci & Pract Mat Res Ctr P Brovki Str 19 Minsk 220072 BELARUS

Dielectric energy storage capacitors are critical components widely used in electronic equipment and power systems due to their advantages of ultrahigh power density and high voltage. Herein, a novel core-shell BaTiO3@MgO (BT@MO) nanostructure was fabricated, in which highly insulating MgO was directly coated on a continuous ferroelectric nanoparticle BaTiO(3)shell through a chemical precipitation method to improve the breakdown strength and electric displacement under high electric field. A large electric displacement (D approximate to 9.8 mu C cm(-2)under 571.4 MV m(-1)) was observed along with a high discharge energy density (Ud approximate to 19.0 J cm(-3)) for BT@MO/P(VDF-HFP) composites, which was 187% higher than that for a P(VDF-HFP) film when the filler content was 3 wt%. The enhancement rate ofU(d)in this study achieved the highest level among the reported results. It was revealed that the highly insulating MgO shell can enhance the breakdown strength by preventing charge injection from electrodes and impeding the development of electrical stress during the breakdown process, as confirmed by the leakage current measurements and the finite element simulations. The core-shell BT@MO structured filler provided an effective way to improve the energy storage properties of the polymer-based dielectrics.

关键词： Magnesia

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