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arXiv 2021年

作者： Zhao, K. Pomes, F. Vowinckel, Bernhard Hsu, T.-J. Bai, B. Meiburg, E. Department of Mechanical Engineering UC Santa Barbara Santa BarbaraCA93106 United States State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Leichtweiß-Institute for Hydraulic Engineering and Water Resources Technische Universität Braunschweig Braunschweig38106 Germany Center for Applied Coastal Research Department of Civil & Environmental Engineering University of Delaware NewarkDE19716 United States

We investigate the dynamics of cohesive particles in homogeneous isotropic turbulence, based on one-way coupled simulations that include Stokes drag, lubrication, cohesive and direct contact forces. We observe a transient flocculation phase characterized by a growing average floc size, followed by a statistically steady equilibrium phase. We analyze the temporal evolution of floc size and shape due to aggregation, breakage, and deformation. Larger turbulent shear and weaker cohesive forces yield elongated flocs that are smaller in size. Flocculation proceeds most rapidly when the fluid and particle time scales are balanced and a suitably defined Stokes number is O(1). During the transient stage, cohesive forces of intermediate strength produce flocs of the largest size, as they are strong enough to cause aggregation, but not so strong as to pull the floc into a compact shape. Small Stokes numbers and weak turbulence delay the onset of the equilibrium stage. During equilibrium, stronger cohesive forces yield flocs of larger size. The equilibrium floc size distribution exhibits a preferred size that depends on the cohesive number. We observe that flocs are generally elongated by turbulent stresses before breakage. Flocs of size close to the Kolmogorov length scale preferentially align themselves with the intermediate strain direction and the vorticity vector. Flocs of smaller size tend to align themselves with the extensional strain direction. More generally, flocs are aligned with the strongest Lagrangian stretching direction. The Kolmogorov scale is seen to limit floc growth. We propose a new flocculation model with a variable fractal dimension that predicts the temporal evolution of the floc size and shape. © 2021, CC BY.

关键词： Flocculation

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Correction to: Modification of a first‑generation solid oxide fuel cell cathode with Co3O4 nanocubes having selectively exposed crystal planes

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Materials for Renewable and Sustainable Energy 2022年第3期11卷 299-299页

作者： Xu, Xi Wang, Chao Fronzi, Marco Liu, Xuehua Bi, Lei Institute of Materials for Energy and Environment College of Materials Science and Engineering Qingdao University Qingdao China State Key Laboratory of Multiphase Flow in Power Engineering International Research Centre for Renewable Energy Xi’an Jiaotong University Xi’an China

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Microalgae bio-oil production by pyrolysis and hydrothermal liquefaction: Mechanism and characteristics

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Bioresource Technology 2023年 376卷 128860页

作者： Ağbulut, Ümit Sirohi, Ranjna Lichtfouse, Eric Chen, Wei-Hsin Len, Christophe Show, Pau Loke Le, Anh Tuan Nguyen, Xuan Phuong Hoang, Anh Tuan Department of Mechanical Engineering Duzce University Düzce81620 Turkey School of Health Sciences and Technology University of Petroleum and Energy Studies Uttarakhand Dehradun248 007 India State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China Department of Aeronautics and Astronautics National Cheng Kung University Tainan701 Taiwan Research Center for Smart Sustainable Circular Economy Tunghai University Taichung407 Taiwan Department of Mechanical Engineering National Chin-Yi University of Technology Taichung411 Taiwan Institute of Chemistry for Life and Health Sciences PSL University France Department of Chemical Engineering Khalifa University P.O. Box 127788 Abu Dhabi United Arab Emirates Zhejiang Provincial Key Laboratory for Subtropical Water Environment and Marine Biological Resources Protection Wenzhou University Wenzhou325035 China Department of Chemical and Environmental Engineering Faculty of Science and Engineering University of Nottingham Malaysia Jalan Broga Selangor Darul Ehsan Semenyih43500 Malaysia Department of Sustainable Engineering Saveetha School of Engineering SIMATS Chennai602105 India School of Mechanical Engineering Hanoi University of Science and Technology Hanoi Viet Nam PATET Research Group Ho Chi Minh City University of Transport Ho Chi Minh City Viet Nam Institute of Engineering HUTECH University Ho Chi Minh City Viet Nam

Microalgae have great potential in producing energy-dense and valuable products via thermochemical processes. Therefore, producing alternative bio-oil to fossil fuel from microalgae has rapidly gained popularity due to its environmentally friendly process and elevated productivity. This current work aims to review comprehensively the microalgae bio-oil production using pyrolysis and hydrothermal liquefaction. In addition, core mechanisms of pyrolysis and hydrothermal liquefaction process for microalgae were scrutinized, showing that the presence of lipids and proteins could contribute to forming a large amount of compounds containing O and N elements in bio-oil. However, applying proper catalysts and advanced technologies for the two aforementioned approaches could improve the quality, heating value, and yield of microalgae bio-oil. In general, microalgae bio-oil produced under optimal conditions could have 46 MJ/kg heating value and 60% yield, indicating that microalgae bio-oil could become a promising alternative fuel for transportation and power generation. © 2023 Elsevier Ltd

关键词： Microalgae

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Two-dimensional self-adapting fast Fourier transform algorithm for nanoparticle sizing by ultrafast image-based dynamic light scattering

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Particuology 2018年第6期16卷 74-84页

作者： Dechuan Zhang Xiaoshu Cai Wu Zhou Institute of Particle and Two-Phase Flow Measurement University of Shanghai for Sdence and TechnologyShanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering (University of Shanghai for Sdence and Technology)Shanghai 200093China

In nanoparticle sizing using the ultrafast image-based dynamic light scattering (UIDLS)method,larger impurities and dark noise from the complementary metal-oxide-semiconductor (CMOS)detector affect measurement *** solve this problem,a two-dimensional self-adapting fast Fourier transform (2D-SAFFT)algorithm is proposed for *** light scattering images of nanoparticles are processed using 2D fast Fourier transforms,and a high-frequency threshold and a low-frequency threshold are then set using the self-adapting algorithm to eliminate the effects of the dark noise of the CMOS detector and the *** signals caused by the dark noise of the CMOS detector and the impurities are cut off using the high-frequency threshold and the low-frequency *** signals without the high- and low-frequency components are then processed again using an inverse Fourier transform to obtain new images without the dark noise and impurities *** mean diameters of the measured nanoparticles can be obtained from images obtained using *** standard latex nanoparticles (46,100, 203,508,994nm)and commercial nanoparticles (antimony-doped tin oxide,indium tin oxide,TWEEN- 80,nano-Fe,and nano-Al2O3)were measured using this new *** show that 2D-SAFFT can effectively eliminate the effects of dark noise from the CMOS detector and the impurities.

关键词： Dynamic light scattering Nanoparticle size Fast Fourier transform algorithm Spectrum segmentation

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Electrochemical oxidation of rhodamine B by PbO_2/Sb-SnO_2/TiO_2 nanotube arrays electrode

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Chinese Journal of Catalysis 2019年第6期40卷 917-927页

作者： Jia Wu Kai Zhu Hao Xu Wei Yan Xi’an XD Switchgear Electric Co. Ltd.Xi’an 710049ShaanxiChina Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049ShaanxiChina

A PbO2/Sb-SnO2/TiO2 nanotube array composite electrode was successfully synthesized and its electrochemical oxidation properties were ***-emission scanning electron microscopy(FE-SEM)and X-ray diffraction(XRD)results showed that the PbO2 coating was composed of anα-PbO2 inner layer and aβ-PbO2 outer *** life measurement indicated that the composite electrode had a lifetime of 815 *** B(RhB)was employed as a model pollutant to analyze the electrocatalytic activity of the *** effects of initial RhB concentration,current density,initial pH,temperature,and chloride ion concentration on the electrochemical oxidation were investigated in *** coupled plasma atomic emission spectroscopy(ICP-AES)results suggested that the concentration of leached Pb^2+in the electrolyte during the electrocatalytic oxidation process can be ***,the degradation mechanism during the electrocatalytic oxidation process was proposed based on the results of solid-phase micro-extraction-gas chromatography-mass spectrometry(SPME-GC-MS).The high electrocatalytic performance of the composite electrode makes it a promising anode for the treatment of organic pollutants in aqueous solution.

关键词： TiO2 nanotube array Electrochemical oxidation Rhodamine B Degradation mechanism

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Error Analysis of Liquid Holdup Measurement in Gas-Liquid Annular flow Through Circular Pipes Using High-Speed Camera Method

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Journal of Shanghai Jiaotong university(Science) 2018年第S1期23卷 34-40页

作者： LIU Li BAI Bofeng School of Nuclear Science and Engineering Shanghai Jiao Tong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, taking the issue of optical distortion into account, an analytical model was proposed to estimate and correct the liquid holdup in gas-liquid annular flow through a circular pipe using high-speed camera method. The error in the liquid holdup measurement generated from different refractive indices among transparent circular pipe, liquid film and air core was firstly theoretically analyzed based on the geometric optics. Experimental tests were then carried out to identify the difference as well as to validate the proposed model. Results indicated that the prediction of the liquid holdup has a good performance with the experimental data(i.e., mean relative error is 4.1%) and the measured liquid holdup is larger than the real one. It was found that the measured liquid holdup is larger than the real one. Generally, when the real liquid holdup gets smaller, the discrepancy between the measured liquid holdup by image and the real liquid holdup becomes more significant. Thus, after measuring the liquid holdup from the images, the value of the measured liquid holdup must be corrected by the present model in order to obtain the real liquid holdup.

关键词： gas-liquid annular flow liquid holdup optical refraction analytical correction

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Electrocatalytically Activating and Reducing N2Molecule by Tuning Activity of Local Hydrogen Radical

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Angewandte Chemie 2023年第20期135卷

作者： Yuanyuan Yang Cejun Hu Dr. Jieqiong Shan Chuanqi Cheng Prof. Lili Han Prof. Xinzhe Li Ruguang Wang Prof. Wei Xie Prof. Yao Zheng Prof. Tao Ling Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and Engineering Tianjin University Tianjin 300072 China Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) Tianjin Key Lab of Molecular Recognition & Biosensing Renewable Energy Conversion and Storage Center College of Chemistry Nankai University Tianjin 300071 China School of Chemical Engineering The University of Adelaide Adelaide SA 5005 Australia State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou 350002 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi An Shi Xi'an 710049 China

Decarbonizing N 2 conversion is particularly challenging, but essential for sustainable development of industry and agriculture. Herein, we achieve electrocatalytic activation/reduction of N 2 on X/Fe−N−C (X=Pd, Ir and Pt) dual-atom catalysts under ambient condition. We provide solid experimental evidence that local hydrogen radical (H*) generated on the X site of the X/Fe−N−C catalysts can participate in the activation/reduction of N 2 adsorbed on the Fe site. More importantly, we reveal that the reactivity of X/Fe−N−C catalysts for N 2 activation/reduction can be well adjusted by the activity of H* generated on the X site, i.e., the interaction between the X−H bond. Specifically, X/Fe−N−C catalyst with the weakest X−H bonding exhibits the highest H* activity, which is beneficial to the subsequent cleavage of X−H bond for N 2 hydrogenation. With the most active H*, the Pd/Fe dual-atom site promotes the turnover frequency of N 2 reduction by up to 10 times compared with the pristine Fe site.

关键词： Carbon Materials Electrocatalysis Metal-Free Catalysts Nitrogen Reduction Reaction

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Enhanced efficiency in Concentrated Parabolic Solar Collector(CPSC) with a porous absorber tube filled with metal nanoparticle suspension

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Green Energy & Environment 2018年第2期3卷 129-137页

作者： Mohammad Hatami Jiafeng Geng Dengwei Jing Mechanical Engineering Department Esfarayen University of Technology (EUT) International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector(CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction(φ), Darcy number(Da) and Rayleigh number(Ra), on the Nusselt number(Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe_3O_4, Al_2O_3, TiO_*** the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.

关键词： Concentrating parabolic solar collector Porous absorber tube Nanofluid Nusselt number Finite Element Method

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Instantaneous liquid and gas leakage flow during plunger lifting process in vertical wells 11

Instantaneous liquid and gas leakage flow during plunger lif...

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11th North American Conference on multiphase Technology

作者： Zhao, K. Bai, B. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Plunger lift is an economical artificial lift method to solve the liquid loading problem in gas wells. Because of the inevitable annular gap between plunger and tube wall, the liquid above plunger may leak downward and the gas may slip upward during lifting process. How to quantitatively describe the gas-liquid counter-current flow sealing property is still challenging to optimize the plunger lift method. In this paper, the liquid leakage and gas slippage were observed experimentally. The transient physical models for gas and liquid leakage were proposed and verified. © 11th North American Conference on multiphase Technology. All rights reserved.

关键词： Liquids

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Photothermal Synergistic Effect Induces Bimetallic Cooperation to Modulate Product Selectivity of CO2Reduction on Different CeO2Crystal Facets

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Angewandte Chemie 2024年第46期136卷

作者： Yuqi Ren Yitao Si Mingyue Du Changjun You Chunyang Zhang Yuan-Hao Zhu Prof. Zhenkun Sun Prof. Kai Huang Prof. Maochang Liu Prof. Lunbo Duan Prof. Naixu Li School of Chemistry and Chemical Engineering Southeast University No.2 Dongnandaxue Road Nanjing 211189 Jiangsu P.R. China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an Shaanxi 710049 P.R. China Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and Environment No.2 Dongnandaxue Road Nanjing 210096 Jiangsu P.R. China

Product selectivity of solar-driven CO 2 reduction and H 2 O oxidation reactions has been successfully controlled by tuning the spatial distance between Pt/Au bimetallic active sites on different crystal facets of CeO 2 catalysts. The replacement depth of Ce atoms by monatomic Pt determines the distance between bimetallic sites, while Au clusters are deposited on the surface. This space configuration creates a favourable microenvironment for the migration of active hydrogen species (*H). The *H is generated via the activation of H 2 O on monatomic Pt sites and migrate towards Au clusters with a strong capacity for CO 2 adsorption. Under concentrated solar irradiation, selectivity of the (100) facet towards CO is 100 %, and the selectivity of the (110) and (111) facets towards CH 4 is 33.5 % and 97.6 %, respectively. Notably, the CH 4 yield on the (111) facet is as high as 369.4 μmol/g/h, and the solar-to-chemical energy efficiency of 0.23 % is 33.8 times higher than that under non-concentrated solar irradiation. The impacts of high-density flux photon and thermal effects on carriers and *H migration at the microscale are comprehensively discussed. This study provides a new avenue for tuning the spatial distance between active sites to achieve optimal product selectivity.

关键词： Photothermal catalysis CO2 reduction Product selectivity Bimetallic active sites Spatial distance

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