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Wall-to-bed heat transfer in supercritical water fluidized bed using CFD-DEM

Particuology 2021年第3期19卷 113-123页

作者： Tianning Zhang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi’an Jiaotong UniversityXi’anShaanxi 710049PR China

Supercritical water fluidized bed(SCWFB)reactors are designed to gasify biomass or coal with high *** this paper,the wall-to-bed heat transfer characteristics in SCWFB are studied using the computational fluid dynamics and discrete element method(CFD-DEM)coupled with a constant heat flux *** different methods are considered to deal with the multiphase heat flux boundary in CFD-DEM because there is currently no single widely accepted ***’s method predicts a more accurate wall-to-bed heat transfer coefficient in SCWFB than Lattanzi’s method according to comparisons of the simulation results with an empirical *** influences of temperature,pressure,velocity,and the solid phase properties,such as the particle diameter,particle heat capacity,particle thermal conductivity,and particle density,on the SCWFB wall-to-bed heat transfer characteristics are studied based on Zhang’s *** simulation results help reveal the SCWFB heat transfer characteristics.

关键词： Supercritical water Fluidized bed Heat transfer DEM-CFD Constant heat flux

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Stall-induced aeroelastic instability of floating offshore wind turbines: Comparison of frequency domain and time domain quasi-steady approaches

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Renewable Energy 2025年 251卷

作者： Meng, Qingshen Yu, Wei Wu, Faming Hua, Xugang Chen, Chao State Key Laboratory of Bridge Engineering Safety and Resilience College of Civil Engineering Hunan University Changsha410006 China Flow Physics and Technology Faculty of Aerospace Engineering Delft University of Technology HS Delft2629 Netherlands Wind Power Business Division CRRC Zhuzhou Institute Co.Ltd Zhuzhou412000 China

With the increasing size of floating offshore wind turbines (FOWTs), stall-induced aeroelastic instability has become a critical issue. This study numerically investigates this instability for FOWTs at stand-still conditions using time and frequency domain approaches. A nonlinear aeroelastic model based on quasi-steady theory and a linearized version are used for time and frequency domain simulations, respectively. Hydrodynamic damping considers both radiation and viscous drag effects. The aeroelastic instability of a stand-still NREL OC3-Hywind 5MW FOWT is analyzed for various inflow yaw misalignment angles. Frequency domain simulation shows rotor edgewise and tower side-side modes exhibit stall-induced instability due to aerodynamic negative damping at specific yaw misalignment and azimuth angles. The platform's yaw mode also shows small negative damping, despite large hydrodynamic damping, while other platform modes remain dynamically stable. Safety margins of FOWTs are analyzed for multi-mode stability, and an active control strategy is proposed to prevent stall-induced instability in all unstable modes. Limit cycle oscillations in the rotor's in-out plane are observed from time domain simulation. Instability regions predicted by both analyses highly overlap, but frequency domain results are more conservative. Blade instability may cause high-frequency vibrations in platform movements with limited amplitudes and severe oscillations in tower structures. © 2025 Elsevier Ltd

关键词： Wind turbines

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Curvature-property coupling governed heat transfer deterioration in supercritical helically coiled tubes: Mechanistic insights and mitigation strategies via structural parametrization

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International Journal of Thermal Sciences 2025年 215卷

作者： Chang, Fucheng Xin, Jiaxing Wu, Xiaoyi Li, Liwei Li, Huixiong Zhu, Yanlin National Key Lab of Aerospace Power System and Plasma Technology School of Mechanical Engineering Xi'an Jiaotong University Xi'an 710049 China China Special Equipment Testing and Research Institute Beijing 100029 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China Shanghai Nuclear Engineering Research & Design Institute Co. Ltd Shanghai 200233 China

The unique thermo-hydrodynamic coupling phenomena in the helically coiled tube (HCT) handling supercritical fluids present both opportunities and challenges for next-generation compact heat exchangers. While the pronounced thermophysical property variations near pseudo-critical temperatures (T_pc) and curvature-induced secondary flows synergistically enhance heat transfer coefficient (HTC), their nonlinear coupling mechanisms may unexpectedly provoke severe heat transfer deterioration (HTD). Through systematic numerical investigations, this study reveals that circumferential wall temperature inhomogeneity (CWTI) exhibits an inverted N-shaped evolution, providing valuable insights for thermal homogenization design near T_pc. The secondary flow Reynolds number (Se), quantifying secondary flow intensity, shows a monotonic increase with decreasing coil diameter (D_c) or inner diameter (D_i), reaching saturation in high-enthalpy regions. Notably, CWTI demonstrates non-monotonic behavior, achieving minimum values near T_pc before manifesting distinct rebound characteristics near T_pc conditions. Parametric analysis establishes that: (1) Elevating heat flux (q) increases Se, reducing D_c boosts it by 50.3 %, and decreasing D_i raises it by 60.0 %. (2) HTD predominantly initiates at the outer wall under high-q conditions, with D_c reduction achieving HTD suppression and 26.9 % enhancement in the local HTC;(3) Reducing the D_i results in a reduction of maximum CWTI by 22.5 %–28.6 %, suggesting that structural parametrization effectively mitigates wall temperature non-uniformity, thus suppressing the HTD. While centered on supercritical water, the dimensionless scaling relationships demonstrate extendibility to other media, with the curvature-property coupling mechanism both elucidating fundamental interactions and guiding robust heat exchanger design. © 2025 Elsevier Masson SA

关键词： Heat transfer deterioration Helically coiled tube Structural parametrization Supercritical fluid Thermo-hydrodynamic coupling

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Operational efficiency improvement in a water supply network: Machine learning-enhanced leakage identification and water resource conservation

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Journal of Water Process engineering 2025年 75卷

作者： Liu, Hongbo Zhang, Junbo An, Wenhui Chen, Yang Yuan, Xiang Zhang, Guosheng Lichtfouse, Eric Ma, Jiale Huang, Jin Tu, Yiqian School of Environment and Architecture University of Shanghai for Science and Technology 516 Jungong Road Shanghai 200093 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an 710049 China Shanghai Urban Construction Design and Research Institute (Group) Co. Ltd. Shanghai 200125 China

Pipeline ruptures in water supply networks can induce significant water loss and may pose risks of water quality deterioration, including potential contamination by pathogens and pollutants. This issue can be addressed by predicting the location of leakage points in the pipeline network and controlling the leakage. Here we designed a hydraulic model for leakage localization using a genetic algorithm-backpropagation neural network, to predict the leakage points in the water supply system of an exposition area consuming 117,211 m³ of water per day in Eastern China. Then, using the model results, pressure-regulating valves were installed in areas with lower network safety. Results show that the error in predicting the leakage points localization ranged from 14.48 m to 121.69 m. The installation of pressure-regulating valves, reduced the average water pressure from 33.54 m to 32.64 m (2.7 %) and, in turn, decreased the simulated background leakage by 9684 m³ of water per day. Compared to traditional acoustic-based methods, the proposed machine learning approach enables more accurate leak localization by leveraging pressure variation features. © 2025 Elsevier Ltd

关键词： Pipeline leakage Point leakage model Pressure monitoring Pressure regulating valve Supply water

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Novel corrosion resistant fluorine-silicon colloidal magnetic fluid: Preparation, characterization and molecular dynamics simulation

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Journal of Magnetism and Magnetic Materials 2025年 628卷

作者： Lu, Jingjing Cui, Hongchao Cheng, Yihang Zhou, Heng Liang, Zhiqi Li, Deicai School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control Technology Beijing Jiaotong University China Beijing Key Laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale School of Mechanical China State Key Laboratory of Tribology Tsinghua University Beijing100084 China

A novel fluorine-silicon colloidal magnetic fluid was prepared using the chemical coprecipitation method and a fluorosilane coupling agent as a surfactant. Material Studio was used to conduct molecular motion simulations of magnetic nanoparticles coated by surfactant, exploring the configuration and energy changes of surfactant molecules on the surface of Fe3O4. In this study, XRD, FTIR, TEM, VSM, XPS, BET, Raman, Zeta potential, DLS, and TG methods were used to characterize the morphology, particle size, and other aspects of the coated Fe3O4 magnetic nanoparticles. The particle size of the coated magnetic nanoparticles is 11.6 nm, with a saturation magnetization of 65.9 emu/g. The saturation magnetization of the prepared magnetic fluid is 10.2 emu/g. The prepared magnetic nanoparticles and fluorine-silicone magnetic fluid can have certain acid and alkali resistance. © 2025 Elsevier B.V.

关键词： Saturation magnetization

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

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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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Al/Cu Enhancement in Marine Anti-Biofouling and Anti-Biocorrosion Performance of High-Entropy Alloys

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Advanced Functional Materials 2025年

作者： Yang, Linlin Zhou, Enze Dong, Yizhe He, Jiajie Tian, Zehong Liu, Bei Wu, Yalin Li, Zhilin Zhou, Zishuai Li, Xiangyu Yu, Bin Fan, Yongqiang Zhang, Mingxing Cui, Miaomiao Lu, Yiping Gu, Tingyue Wang, Fuhui Xu, Dake State Key Laboratory of Digital Steel Northeastern University Shenyang110819 China Northeastern University Shenyang110819 China School of Materials Science and Engineering Dalian University of Technology Dalian116024 China Department of Chemical and Biomolecular Engineering Institute for Corrosion and Multiphase Technology Ohio University AthensOH45701 United States

Antibacterial alloys are designed to mitigate biofouling, which is a strategy for combining the defense and function properties of alloys in complex biological environments. However, the current approaches are unable to overcome the issue of microbiologically influenced corrosion (MIC), because antibacterial performances mostly benefit from the excessive dissolution of antibacterial elements in alloys. Herein, a series of AlxCoCrCuFeNi high-entropy alloys (molar fractions x = 0, 0.1, 0.3, 0.5) are designed. Benefiting from the rigorous management of Al and Cu components, Al0.3HEA achieved a 94.1% anti-biofilm rate against Pseudomonas aeruginosa and an Rp value 20 times higher than that for Al0HEA, effectively balancing anti-biofouling and anti-MIC properties. Specifically, the Cu element induces cell membrane damage and intracellular reactive oxygen species. Al acts as a stabilizer of the Cu-enriched phase by decreasing the potential difference between the FeCoCrNi-phase and the Cu-enriched-phase, impeding the excessive dissolution of the Cu-enriched phase while maintaining excellent anti-biofouling performance. Additionally, Al enhances the components of Al and Cr oxides in passive films, providing robust defense against corrosive species, and ultimately enhancing the MIC resistance of Al0.3HEA. This work presents a new strategy for designing MIC-resistant materials with broad applications in marine engineering. © 2025 Wiley-VCH GmbH.

关键词： Biofilms

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A second-order phase field-lattice Boltzmann model for two-phase flows with moving contact line and soluble surfactants

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International Communications in Heat and Mass Transfer 2025年 165卷

作者： Zhang, Shiting Wang, Xifeng Zhu, Yuqi Hu, Yang He, Qiang Li, Qianping Li, Decai Beijing key laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing 100044 China State Key Laboratory of Tribology in Advanced Equipment Tsinghua University Beijing 100084 China

This paper presents a second-order phase field-lattice Boltzmann model for two-phase flows with moving contact lines and soluble surfactants. The phase field and surfactant concentration field are governed by second-order conservative Allen-Cahn equations, while the velocity-based Navier–Stokes equations describe the flow field. The model ensures that surfactant concentration variations do not affect the order parameter distribution, preventing sharpening effects. An approximate explicit equation of state, derived from the Gibbs–Duhem equation, defines the relationship between surfactant concentration and interfacial tension, which is incorporated into Young's equation to determine the equilibrium contact angle. A geometrically defined wetting boundary condition addresses the moving contact line problem. Model validation includes verifying the equation of state using the Laplace law and assessing the equilibrium contact angle based on the geometric properties of droplets spreading on planar surfaces. Simulations explore the effects of wettability, surfactant concentration, and flow parameters on droplet dynamics, including Couette and Poiseuille flows, gravity-driven droplet motion, and droplet behavior on rough surfaces. The study results indicate that increasing surfactant concentration reduces the contact angle on hydrophilic surfaces while increasing it on hydrophobic surfaces, highlighting its impact on surface wettability. © 2024

关键词： Lattice Boltzmann method Moving contact line Phase-field method Soluble surfactant Two-phase flow Wetting boundary condition

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Fe-saturated polyaniline adsorbent repurposed for carboxylic acid drugs removal: A sustainable strategy from ferric waste to water remediation

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Separation and Purification Technology 2025年 371卷

作者： Shi, Bofang Fu, Xiaojie Li, Hang Jamshed, Muhammad Yu, Qi Li, Mingtao Yang, Honghui Xi'an Key Laboratory of Sustainable Energy Materials Chemistry Department of Applied Chemistry School of Chemistry Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China China Coal Energy Research Institute Co. Ltd Xi'an 710201 China Xi'an Taijin New Energy Technology Co. Ltd Xi'an 710201 China

The removal of non-steroidal anti-inflammatory drugs (NSAIDs) via adsorption necessitates the development of advanced adsorbents that harmonize efficiency with cost-effectiveness. Herein, a circular and economic approach is proposed by repurposing Fe-saturated polyaniline (Fe-PANI) waste into a high-performance adsorbent for carboxylic acid drug removal. The Fe-PANI exhibited high equilibrium adsorption capacities of 196.8 mg/g (diclofenac, DCF), 75.2 mg/g (naproxen, NPX), and 40.5 mg/g (ibuprofen, IBP) under neutral conditions (pH 6.0), outperforming the performance of pristine PANI material. Adsorption experiments revealed pseudo-second-order kinetics and Langmuir monolayer adsorption behavior. The pH values and the presence of carbonate species (CO32– and HCO3–) were identified as critical factors affecting adsorption process. Experimental evidence and density functional theory (DFT) calculations confirmed that the incorporation of Fe2+/Fe3+ into PANI significantly altered its electronic structure, facilitating synergistic adsorption via Fe-carboxylate coordination, π-π stacking, and proton-enhanced electrostatic interactions. The used adsorbent was successfully regenerated via a Fe-mediated heterogeneous Fenton reaction (0.025 mol/L H2O2, pH 6.0), retaining 82% of its adsorption capacity after three cycles. This dual-functional strategy effectively utilizes hazardous metal-loading waste and addresses drug pollution through adsorption and oxidative regeneration, providing a sustainable approach for water remediation technologies. © 2025 Elsevier B.V.

关键词： Carboxylation

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Ferrites boosting photocatalytic hydrogen evolution over graphitic carbon nitride: a case study of(Co, Ni)Fe_2O_4 modification

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Science Bulletin 2016年第4期61卷 292-301页

作者： Jie Chen Daming Zhao Zhidan Diao Miao Wang Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

The charge cartier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydrogen evolution over graphitic carbon nitride （g-C3N4） were greatly promoted with the earth-abundant ferrites （Co, Ni）Fe2O4 modification. CoFe2O4 was further demonstrated to be a better modifier for g-C3N4 as compared to NiFe2O4, due to the more efficient charge carrier transfer as well as superior surface oxidative catalytic activity. When together loading CoFe2O4 and reductive hydrogen production electrocatalyst Pt onto g-C3N4, the obtained Pt/g-C3N4/CoFe2O4 photocatalyst achieved visible-light （2 〉 420 nm） hydrogen production rate 3.5 times as high as Pt/g-C3N4, with the apparent quantum yield reaching 3.35 % at 420 nm.

关键词： Graphitic carbon nitride FerritesPhotocatalytic water splitting Solar hydrogenconversion

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