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Nanoparticle-induced drag reduction for polyacrylamide in turbulent flow with high Reynolds numbers

Chinese Journal of Chemical engineering 2023年第4期56卷 290-298页

作者： Xiaoping Li Jiaxin Pan Jinwen Shi Yanlin Chai Songwei Hu Qiaorong Han Yanming Zhang Xianwen Li Dengwei Jing State Key Laboratory of Multiphase Flow in Power Engineering&International Research Center for Renewable Energy Xi'an Jiaotong UniversityXi'an 710049China Oil and Gas Technology Research Institute of Petrochina Changqing Oilfield Company Xi'an 710018China

Although having been increasingly studied, there is still controversy as to when the addition of nanoparticles could improve the drag reduction performance of polymer drag reducer and particularly what is the underlying mechanism from the fluid dynamics viewpoint. The drag reduction effects of adding SiO_(2) nanoparticles to various polymer polyacrylamide(PAM) solutions were examined in this *** optimal combination of SiO_(2) nanoparticles with cationic polyacrylamide was ***,the addition of SiO_(2) nanoparticles to cationic polyacrylamide solution was shown to be quite efficient for reducing drag, but only at higher flow rates with Reynolds numbers more than 6000, below which the nanoparticle addition is even negative. The addition of SiO_(2) nanoparticles to the PAM solution is supposed to play a dual role. The first is an increase in flow resistance caused by the Brownian motion of nanoparticles, while the second is a decrease in flow resistance caused by acting as nodes to protect the polymer chain from shear-induced breaking under high shear action. At optimal nanoparticle concentration and under higher Reynolds numbers, the later effect is dominant, which could improve the drag reduction performance of polymer drag reducers. Our work should serve as a guide for the application of natural gas fracturing, where the flow rate is frequently very high.

关键词： Drag reduction SiO_(2)nanoparticle Cationic polymer Brownian motion

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Performance Analysis of Cooling Wall of Supercritical CO_(2) Coal-Fired Plants

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Journal of Thermal Science 2022年第6期31卷 1881-1890页

作者： WANG Yanjuan YU Binhui GAO Shuo LIU Qibin XU Jinliang The Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing 102206China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Using supercritical CO_(2)(S-CO_(2)) instead of water steam as heat transfer fluid for coal-fired power plants is another way to further improve the power generation efficiency. In this paper, a multi-field coupling model that integrates fluid flow, heat transfer and thermal stress is proposed to solve the complex problem. The effects of the key operating parameters on the performances of the cooling wall are numerically investigated. More details of the characteristics of fluid dynamics, thermal stress, pressure drop, coupled heat transfer and the whole flow and temperature fields in the S-CO_(2) cooling wall are revealed and discussed. A comparison study is made between the cooling wall tube and waterwall tube. Both temperature and thermal deformations of cooling wall tube are much higher than that of water. Numerical simulation results indicate that inclination angle has little effects on the temperature distribution, while increase of pressure drop is obvious as the inclination angle increases. Increasing tube diameter can effectively reduce both the pressure drop and the temperature of the cooling wall tube. As a result, a new insight is introduced for the design of S-CO_(2) power cycle.

关键词： supercritical CO_(2) cooling wall coal-fired power plant heat transfer

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Progress and challenge of functional single-atom catalysts for the catalytic oxidation of volatile organic compounds

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Chinese Chemical Letters 2024年第9期35卷 83-91页

作者： Zeyu Jiang Yadi Wang Changwei Chen Chi He Department of Environmental Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China National Engineering Laboratory for VOCs Pollution Control Material&Technology University of Chinese Academy of SciencesBeijing 101408China

The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of efficient catalysts for use in this *** this regard,the development and utilization of single-atom catalysts(SACs)in VOCs decomposition is a rapidly expanding research *** can be employed as potential catalysts for oxidizing VOC molecules due to their optimal utilization efficiency,unique atomic bonding structures,and unsaturated *** has been achieved,while the challenges surrounding precise regulation of the microstructures of SACs for improving their low-temperature efficiency,stability,and product selectivity under practical conditions are ***,elucidating structure-performance relationships and establishing intrinsic modulating mechanisms are urgently required for guiding researchers on how to synthesize effective and stable functional SACs ***,recent advances in the design and synthesis of functional SACs for application in the catalytic oxidation of VOCs are *** experimental and theoretical studies revealing higher efficiency,stability,and selectivity of as-prepared functional SACs are being ***,the future perspectives in terms of promising catalysts with multi-sized composite active sites and the illustration of intrinsic mechanism are *** rapid intelligent screening of applicable SACs and their industrial applications are also discussed.

关键词： Single-atom catalysts VOCs catalytic oxidation Hydrocarbon activation Oxygen species transformation Surface chemistry Intrinsic mechanism

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A New Structure of Cooling Wall Tube for Supercritical CO_(2)Coal-Fired power Plants

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Journal of Thermal Science 2023年第3期32卷 1239-1250页

作者： WANG Yanjuan GAO Shuo JIANG Qiongqiong LI Yi LIU Qibin XU Jinliang The Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing 102206China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

In terms of developing supercritical CO_(2)(sCO_(2))coal-fired power plants,enhancing cooling wall performance is one of significant factors to improve system *** this paper,a new cooling wall tube structure is proposed to match the non-uniform heat flux(NUH)with the thermal resistance by changing the cooling wall tube eccentricity.A three-dimensional multi-physical coupling model of cooling wall is constructed to compare the novel structure to the conventional *** properties of fluid dynamics,thermal stress,coupled heat transfer and cooling wall deformation are *** contrast to the traditional structure,the maximum temperature and circumferential temperature difference(CTD)of the proposed structure can be reduced by 2%and 27.4%,*** essential working parameters related to the performances of the cooling wall tube are *** maximum temperature of the new structure is reduced by 8-13 K and the maximum thermal stress is reduced by about 10%-15%under all the simulated working conditions when the eccentricity changes from 0 to *** proposed structure can effectively reduce the maximum temperature and circumferential temperature gradient under ***,a novel insight is put out for the design and optimization of the cooling wall tube in coal-fired power plants.

关键词： supercritical carbon dioxide cooling wall tube thermal-hydraulic structural coupling supereritical heat transfer

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Simulation of the dynamic behavior of droplet impact on the microstructure surface 1

Simulation of the dynamic behavior of droplet impact on the ...

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1st International Conference on Fluid Dynamics and Computational Science, FDCS 2022

作者： Yang, Jianhua Gao, Ming Sun, Hailin Liu, Zhennan Zhang, Kaiyuan Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering The University of Shanghai for Science and Technology Shanghai200093 China

The problem of droplets impacting rough wall has always been a hot spot in the engineering field. In this paper, the single-component multiphase lattice Boltzmann method is used to construct the wall microstructure, and the dynamic behavior characteristics of droplets impacting rough walls are simulated. The results show that the final state of a droplet impacting rectangular microstructure shows that the hydrophilic surface is more hydrophilic and the hydrophobic surface is more hydrophobic, and compared with the smooth surface, the microstructure surface hinders the rebound of the droplet, and the application of microstructure on the wall can promote the spreading of a droplet on the wall. © 2023 Institute of Physics Publishing. All rights reserved.

关键词： Drops

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EXPERIMENTAL STUDY ON GAS-LIQUID TWO-PHASE flowS IN AN AREATION TANK BY USING IMAGE TREATMENT METHOD

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Journal of Hydrodynamics 2008年第5期20卷 650-655页

作者： CHENG Wen LIU Wen-hong HU Bao-wei WAN Tian State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China Environment Research Institute Xi＇an University of Technology Xi＇an 710048 China Environment Research Institute Xi＇an University of Technology Xi＇an 710048 China

Particle Image Velocimetry （PIV） technique was employed to study experimentally gas-liquid two-phase flow in an aeration tank. In terms of the PIV principles, an algorithm of PIV based on the Fast Fourier Transformation （FFT） was worked out. The PIV program was developed and verified, and then was used to measure three kinds of states in the testing device. The program was also used to calculate and analyze the related parameters. The experimental data indicate that the bubbles in testing device have the longest resident time and stronger turbulent intensity for the gas-liquid two-phase flow in a special case （Case 3）, resulting in great increase of the oxygen transferring speed and efficiency, whereby providing the basis for the selection design of aeration tank.

关键词： gas-liquid two-phase flow Particle Image Velocimetry （PIV） Fast Fourier Transformation （FFT） aeration tank

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POD analysis on vortical structures in MVG wake by Liutex core line identification

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Journal of Hydrodynamics 2020年第3期32卷 497-509页

作者： Xiang-rui Dong Xiao-shu Cai Yinlin Dong Chaoqun Liu School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering Shanghai 200093China Department of Mathematics University of Central ArkansasConway 72035USA Department of Mathematics University of Texas at ArlingtonArlington 76019USA

The Liutex core line method, first combined with the snapshot proper orthogonal decomposition (POD), is utilized in a supersonic micro-vortex generator (MVG) wake flow at Ma = 2.5 and Reθ = 5 760 to reveal the physical significance of each POD mode of the flow field. Compared with other scalar-based vortex identification methods, the Liutex core line identification is verified to be the most appropriate approach that is threshold-free and provides full information of a fluid rotation motion. Meanwhile, the Liutex integration is employed to quantitatively track the evolution of the vortices in MVG wake and is applied to the determination of the effective control section of the MVG wake for the optimization study of MVG design. The physical mechanism of each POD mode for multi-scale and multi-frequency vortical structures is investigated by using Liutex core line identification to give some revelations. For the mean mode (mode 0) indicating the time-averaged velocity flowfield of the MVG wake flow, a pair of primary counter-rotating streamwise vortices and another pair of secondary vortices is uniquely identified by two pairs of Liutex core lines with Liutex magnitude. In contrast, mode 1 is featured by a fluctuated roll-up motion of streamwise vortex, and the streamwise component of the MVG wake is demonstrated to be dominant in terms of the total kinetic energy contribution. Meanwhile, a dominant shedding frequency of St = 0.072 is detected from the temporal behavior of mode 2, which has the organized arc-shaped vortex structures shedding from MVG induced by the K-H instability. Additionally, mode 4 subjects to low-frequency oscillations of the wall vortices and thus takes a relatively lower frequency of St = 0.044.

关键词： Proper orthogonal decomposition(POD) vortex identification Liutex vortex core lines micro-vortex generator(MVG)

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Study on boiling heat transfer mechanism based on microlayer evaporation theory 6

Study on boiling heat transfer mechanism based on microlayer...

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6th International Conference on Fluid Mechanics and Industrial Applications, FMIA 2022

作者： Dong, Wu-Han Gao, Ming Shen, Zhong-Xiang Zhang, Li-Xin Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

Based on dynamic microlayer evaporation model. Heat transfer mechanism of nuclear boiling and microlayer thickness under single bubble on heated surface. It has a lot to do with the temperature of the wall. Therefore, this paper studies the mechanism of bubble microlayer and makes comparative analysis with its experiments. It is helpful to master nuclear boiling heat transfer more comprehensively. In the study of individual bubble microlayer thickness. The effects of time and radius on wall temperature are considered in this paper. The theoretical formula of initial thickness of microlayer is deduced. The theoretical formula is compared with the experimental data of microlayer evaporation under the nucleation bubble. It was found that the experimental data fell within ±25% of the formula range. It is consistent with the previous experimental research. © Published under licence by IOP Publishing Ltd.

关键词： Evaporation

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Nanomaterials for renewable hydrogen production,storage and utilization

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Progress in Natural Science:Materials International 2012年第6期22卷 522-534页

作者： Samuel S.Mao Shaohua Shen Liejin Guo Lawrence Berkeley National Laboratory and Department of Mechanical Engineering University of California at Berkeley.BerkeleyCA 94720United States Lawrence Berkeley National Laboratory and Department of Mechanical Engineering University of California at Berkeley.BerkeleyCA 94720.United States International Research Center for Renewable Energy.State Key Laboratory of Multiphase Flow in Power Engineering.Xi'an Jiaotong University International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

An ever growing demand for energy coupled with increasing pollution is forcing us to seek environmentally clean alternative energy resources to substitute fossil *** rapid development of nanomaterials has opened up new avenues for the conversion and utilization of renewable *** article reviews nanostructured materials designed for selected applications in renewable energy conversion and *** review is based on the authors’ research,with particular focus on solar hydrogen production,hydrogen storage and hydrogen *** topics include photoelectrochemical(PEC) water splitting and photocatalytic hydrogen production, solid-state hydrogen storage,and proton exchange membrane fuel cells(PEMFCs).It is expected that the rational design of nanomaterials could play an important role in achieving a renewable energy based economy in the coming decades.

关键词： Nanomaterials Renewable energy Hydrogen production Fuel cell Hydrogen storage

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Continuous hydrogen production by biomass gasification in supercritical water heated by molten salt flow: System development and reactor assessment

Continuous hydrogen production by biomass gasification in su...

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作者： Xiao, Peng Guo, Liejin Zhang, Ximin Zhu, Chao Ma, Shaohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 Shaan Xi Province China

Hydrogen production by biomass gasification using solar energy is a promising approach for overcoming the drawbacks of fossil fuel utilization, but the storage of discontinuous solar flux is a critical issue for continuous solar hydrogen production. A continuous hydrogen production system by biomass gasification in supercritical water using molten-salts-stored solar energy was proposed and constructed. A novel double tube helical heat exchanger was designed to be molten salts reactor for hydrogen production. Model compounds (glycerol/glucose) and real biomass (corn cob) were successfully gasified in this molten salts reactor for producing hydrogen-rich gas. The unique temperature profiles of biomass slurry in the reactor were observed and compared with that of conventional electrical heating and direct solar heating approaches. Product gases yield, gasification efficiency and exergy conversion efficiency of the reactor were analyzed. The results showed that the performances of reactor were determined by feedstock style, biomass concentration, residence time and biomass slurry temperature profiles. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Biomass

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