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Eulerian–Lagrangian simulation of bubble coalescence in bubbly flow using the spring-dashpot model

Chinese Journal of Chemical engineering 2017年第3期25卷 249-256页

作者： Jing Xue Feiguo Chen Ning Yang Wei Ge State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesP.O.Box 353Beijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The Eulerian–Lagrangian simulation of bubbly flow has the advantage of tracking the motion of bubbles in continuous fluid, and hence the position and velocity of each bubble could be accurately acquired. Previous simulation usually used the hard-sphere model for bubble–bubble interactions, assuming that bubbles are rigid spheres and the collisions between bubbles are instantaneous. The bubble contact time during collision processes is not directly taken into account in the collision model. However, the contact time is physically a prerequisite for bubbles to coalesce, and should be long enough for liquid film drainage. In this work we applied the spring-dashpot model to model the bubble collisions and the bubble contact time, and then integrated the spring-dashpot model with the film drainage model for coalescence and a bubble breakage model. The bubble contact time is therefore accurately recorded during the collisions. We investigated the performance of the spring-dashpot model and the effect of the normal stiffness coefficient on bubble coalescence in the *** results indicate that the spring-dashpot model together with the bubble coalescence and breakage model could reasonably reproduce the two-phase flow field, bubble coalescence and bubble size distribution. The influence of normal stiffness coefficient on simulation is also discussed.

关键词： Bubble column Spring-dashpot model CoalescenceBreak-up Bubble size distribution

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A comprehensive model for uniform heat flux inside cavity receiver with air-carbon mixture

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Energy Procedia 2017年 142卷 177-183页

作者： Yabin Jin Jiabin Fang Jinjia Wei Xinhe Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

Cavity receiver is one of the main components of efficient concentrating solar collector systems. It has the ability to operate at relatively higher temperature and efficiency. The safety and thermal efficiency of solar cavity receiver can affect the efficiency of the whole power system. However, the non-uniform distribution of heat flux and temperature inside the cavity tends to cause the operation instability and bring damage to the tube as well. In the present work, a comprehensive numerical model was developed by coupling Monte Carlo Ray Tracing (MCRT) and Finite Volume Method (FVM) to simulate the thermal performance of a 2D square solar cavity filled with air-carbon particle mixture. Firstly, the complicated photon transmission in the air-carbon particle mixture absorber is simplified as the transmission process in the statistically homogenous and isotropic turbid media. The solar heat flux distribution from the aperture to the wall is simulated by MCRT, and the photo-thermal convection process in the cavity receiver is modeled by FVM. Then the two parts are coupled in the cavity receiver by transferring the absorbed energy computed by MCRT to FVM, and this energy is applied as a source term of the energy equation in the FVM part. Based on this model, the temperature and heat flux characteristics of the cavity receiver were studied at various carbon densities. The result indicated that the air-carbon particle mixture can actively take part in the radiation and it appears that it has a remarkable effect on the temperature homogenization. It decreases the temperature of wall 3 dramatically and increases the temperature of wall 2 and wall 4. The relationships between the temperature unevenness and the number particle density were also analyzed. The temperature unevenness on the wall 3 drops most with the increase of number density of carbon particle, from 25.0K to 2.4K. The unevenness of temperature on the top and bottom walls also decreases slightly by 3K. In ad

关键词： solar cavity receiver non-uniform air-carbon particle mixture homogenization Monte Carlo ray tracing Finite volume method

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Experimental study on heat transfer to supercritical CO2 flowing in vertical upward tube at medium mass flux

Experimental study on heat transfer to supercritical CO2 flo...

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ASME 2017 Nuclear Forum, NUCLRF 2017, collocated with the ASME 2017 Power Conference Joint with ICOPE 2017, the ASME 2017 11th International Conference on Energy Sustainability, and the ASME 2017 15th International Conference on Fuel Cell Science, engineering and Technology

作者： Zhang, Qian Li, Huixiong Kong, Xiangfei Zhang, Jun Lei, Xianliang Zhang, Weiqiang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'anShaanxi China North Carolina State University United States Burlington Laboratory 3144 North Carolina State University RaleighNC27607 United States

ISBN: (纸本)9780791840597

An experimental study was performed on heat transfer characteristics of supercritical pressure CO2 (SC-CO2) flowing at medium mass flux conditions in a vertically-upward tube of 16 mm inner diameter at the Heat Transfer and flow test loop of Supercritical CO2 (HTF-SCO2) in Xi’an Jiaotong University. Experimental parameters included the pressure ranging from 7.5 to10.5 MPa, the mass flux of 400-600 kg/m2s, and the heat flux of 20-100 kW/m2. Based on the experimental data, effects of mass flux, heat flux and operation pressure on heat transfer characteristics of SC-CO2 were thoroughly discussed. With the decrease of mass flux and increase of heat flux, heat transfer characteristics of SC-CO2 becomes worse and worse. The wall temperature rises to high levels with the occurrence of a wall temperature peak and the wall temperature peak also rises remarkably with the decrease in mass flux and increase in heat flux. Especially, effect of pressures on the heat transfer of SC-CO2 was found to be quite different from that previously reported in literature. When the heat flux is low (such as 30 kW/m2), the HTD was diminished with the increase in pressures, but when the heat flux is up to 50 kW/m2, the HTD is surprisingly intensified by the increase of pressure. The buoyancy effect was considered to explain this distinct influence of pressure on the heat transfer of SC-CO2 by employed a non-dimensional parameter Bu. With the increase of pressure, buoyancy effect was diminished owing to the decrease of density difference between fluids near the wall and the center. When heat flux was lower, the Bu was located between 5×10-6 and 10-4, where buoyancy effect impaired heat transfer, so the heat transfer coefficient increased by rising pressure. But when heat flux was larger, the Bu was above 10-4, where buoyancy effect began to enhance heat transfer, as a result, the heat transfer coefficient was reduced by weakened buoyancy effect because of the increase of pressure (CSPE). Copyrig

关键词： Heat flux

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Flame brush thickness of premixed turbulent flames: Hydrodynamic theory versus experiments 9

Flame brush thickness of premixed turbulent flames: Hydrodyn...

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9th International Conference on Modeling and Diagnostics for Advanved Engine Systems, COMODIA 2017

作者： Zhang, M. Patyal, A. Fogla, N. Wang, J.H. Huang, Z.H. Matalon, M. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

The effect of varying turbulence intensities on the flame brush thickness is investigated numerically using a hybrid Navier-Stokes/front-tracking methodology in the context of the hydrodynamic theory. Two configurations, namely planar and Bunsen, are chosen with the latter used for direct comparison with experimental OH-PLIF Bunsen flame images. The Darrieus-Landau influences are controlled through the mixture Markstein length and the flame brush is analyzed under two regimes, sub- and supercritical based on the absence/presence of the hydrodynamic instability. In the planar configuration at low intensities, the sub-critical flame brush retains its near flat shape, while the super-critical flame brush forms a highly corrugated structure reminiscent of the cusped-like flames that result in the laminar setting. With increasing turbulence levels, these effects start to gradually diminish as the flame becomes dominated by velocity fluctuations arising from the turbulent field, finally leading to nearly identical behavior in both regimes for very high intensities. Unlike the planar flame, the sub-critical Bunsen flame surface is dominated by large wrinkles with a more rounded shape while the super-critical flame highlights the formation of cusp-like structures on its surface. Numerical verification of the Bunsen flame brush thickness shows a good qualitative match with experimental tests for turbulent CH4/air flames. The good agreement indicates the qualitative prediction capabilities of the hydrodynamic model. Copyright © 2017 by the Japan Society of Mechanical Engineers.

关键词： Navier Stokes equations

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Optimization design of flue gas temperature for Low-Low Temperature Electrostatic Precipitator

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Journal of Physics: Conference Series 2019年第1期1300卷

作者： Ke Sun Yu Yan Jiahao Jiang Lei Deng State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China Huadian Electric Power Research Institute Co. LTD. Hangzhou 310030 China

Low temperature corrosion is one of the key issues in application of low-low temperature electrostatic precipitator. The concentration of SO3 affects the acid dew point temperature of flue gas. The exhaust temperature after the air preheater should be higher than the acid dew point temperature. The residual heat of flue gas is fully utilized by the low-temperature economizer. The efficiency of low-low temperature electrostatic precipitator is improved by the comprehensive effect of the condensation of SO3 on the surface of the fine particles, the decrease of the specific resistance of the particles and the agglomeration of the fine particles.

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Experimental Study on Heat Transfer Characteristics of Static Flash Evaporation Process

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Energy Procedia 2017年 105卷 4776-4781页

作者： Qingzhong Yang Dan Zhang Daotong Chong Yu Wang Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an Shaan

An experimental study on flash evaporation process in static flash evaporation of aqueous NaCl solution was presented. Experiments were carried out with initial concentration of waterfilm varied from 0 to 0.15, initial height from 0.1 to 0.4 m, and superheat from 1.8 to 49.5 K. Instant superheat was the driving force during flash evaporation. A negative correlation was found between temperature drop rate and instant superheat. Instant heat transfer coefficient increased with the increase of instant superheat. A peak value of instant superheat existed during static flash. The evolution of instant superheat was affected by initial superheat, or initial height, or initial concentration of waterfilm.

关键词： Static flash evaporation Instant superheat Aqueous NaCl solution temperature drop rate

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Ionic Liquids: Molecular Insights into the Regulatable Interfacial Property and flow Behavior of Confined Ionic Liquids in Graphene Nanochannels (Small 29/2019)

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Small 2019年第29期15卷

作者： Yanlei Wang Chenlu Wang Yaqin Zhang Feng Huo Hongyan He Suojiang Zhang Beijing Key Laboratory of Ionic Liquids Clean Process CAS Key Laboratory of Green Process and Engineering State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

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Oxygen-doped carbon host with enhanced bonding and electron attraction abilities for efficient and stable SnO_2/carbon composite battery anode

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Science China Materials 2018年第8期61卷 1067-1077页

作者： Zhen Geng Bing Li Hezhi Liu Hong Lv Qiangfeng Xiao Yongjun Ji Cunman Zhang Clean Energy Automotive Engineering Center Tongji UniversityShanghai 201804China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China General Motors Research and Development Center WarrenMI 48090USA

The coupling between electrochemically active material and conductive matrix is vitally important for high efficiency lithium ion batteries （LIBs）. By introducing oxygen groups into the nanoporous carbon framework, we accom- plish sustainably enhanced electrochemical performance for a SnO2/carbon LIB. 2-5 nm SnO2 nanoparticles are hydro- thermally grown in different nanoporous carbon frameworks, which are pristine, nitrogen- or oxygen-doped carbons. Compared with pristine and nitrogen-doped carbon hosts, the SnO2/oxygen-doped activated carbon （OAC） composite ex- hibits a higher discharge capacity of 1,122mAhg^-1 at 500 mA g^-1 after 320 cycles operation and a larger lithium storage capacity up to 680 mAhg-I at a high rate of 2,000 mA g^-1. The exceptional electrochemical performance originated from the oxygen groups, which could act as Lewis acid sites to attract electrons effectively from Sn during the charge process, thus accelerating reversible conversion of Sn to SnO2. Meanwhile, SnO2 nanoparticles are effectively bonded with carbon through such oxygen groups, thus preventing the electrochemical sintering and maintaining the cycling stability of the SnO2/OAC composite anode. The high electrochemical performance, low biomass cost, and facile preparation renders the SnO2/OAC composites a promising candidate for anode materials.

关键词： tin oxide nanoporous carbon functional groups anode materials lithium-ion batteries

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Experimental Study on Cohesiveness Characteristics of Raw Cement Ash at Moderate Temperature

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Energy Procedia 2017年 105卷 4674-4679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

Raw cement ash deposition in SP boilers gives rise to serious operation problems. In the present, mechanism of raw cement ash deposition is still unclear because the ash components, gas atmosphere and gas temperature are quite different from existing studies. The characteristics of cohesiveness of raw cement ash in moderate temperature were investigated in a lab-scale electric furnace. Three typical raw cement ashes were selected as samples, three base plates, including rough steel plate, smooth steel plate, organic glass plate were studied. Ball-impacting method was adopted to evaluate the cohesiveness of ash. Experimental results show that, the ash cohesiveness is mainly dependent on the components of ash, and the material property of base plate, while it exhibits little relationship with the roughness of the plate surface. Low-melting substances appear during ash deposition on steel plate. The results reveal that ferrum possibly has catalytic to some low-melting substances forming.

关键词： deposition cohesiveness roughness low-melting sunbstances

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Excess thermodynamic properties and FTIR studies of binary of 1, 3-dichlorobenzene with alkyl acetates (C1–C5) at different temperatures

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Chemical Data Collections 2020年 29卷

作者： R. Raju S. Ravikumar R. Gerald Arokiaraj S. Karlapudi K. Sivakumar V. Pandiyan Department of Physics Nehru Memorial College (Autonoums) Puthanampatti 621 007Tamil Nadu India. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 P. R. China. Department of Chemistry S.V.Arts Degree & P.G.College (T.T.D'S) Tirupati 517502 A.P India

Densities ( ρ ) and speed of sound ( u ) have been reported for the binary mixtures containing 1, 3- dichlorobenzene (1, 3-DCB) with methyl acetate, ethyl acetate, propyl acetate, butyl acetate and pentyl acetate at four different temperatures ( T = 303.15, 308.15, 313.15 and 318.15 K) and at atmospheric pressure. The experimental data of densities and speeds of sound has been further utilized to calculate excess molar volume ( V m E ) and excess isentropic compressibility ( κ S E ) the excess properties have been fitted to Redlich-Kister equation. Further, V m E results have also been discussed by using Prigogine–Flory–Patterson (PFP). The experimental speeds of sound data in the present investigated mixtures were compared with various theoretical models like collision factor theory (CFT) and free length theory (FLT) to check their relative merits of pure component properties. Moreover, the experimental excess functions were correlated in terms of FTIR spectral analysis.

关键词： Binary mixtures Densities Ester Halogenated benzene Speed of sound FTIR

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