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Numerical simulation on characteristics of hydrodynamics, interphase and wall to bed heat transfer in a pseudo 2D spouted bed using supercritical CO_(2) as fluidizing agent

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Particuology 2025年第1期96卷 106-125页

作者： Kun Jiang Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710049China

By employing the Eulerian-Eulerian Two Fluid Model, the effect of different particle size, supercritical CO_(2) (scCO_(2)) velocity at slit jet (U_(jet)) and initial bed height on the macroscopic characteristics (i.e., fountain morphology, profiles of particle velocity, momentum transfer characteristics among particles, transient temperature evolutions of particles, interphase heat transfer coefficient and wall to bed heat transfer characteristics) in the pseudo 2D rectangular spouted bed using scCO_(2) as fluidizing agent is numerically studied in detail herein. Considering there are currently no relevant visualized experiments reported using scCO_(2) as a fluidized agent due to the extreme operating pressure of CO_(2) (25 MPa in this paper) under supercritical conditions, present numerical model was validated with experimental data by using air as the fluidizing agent, confirming simulated instantaneous volume fraction distribution of air and transient temperature evolutions of particles basically consistent with the experiments. Numerical results reveal some of the internal relations among hydrodynamics characteristics in bed, momentum transfer characteristics among particles and relevant heat transfer behaviours. Results show larger Ujet and smaller particle size will accelerate the particles' translational motion in spout, spout core and fountain core zone. Larger particle concentration will promote inter-particle collisions while suppress the kinetic motion of particles in above zones. Decrease the particle size will enhance interphase convective heat transfer coefficient, while increasing U_(jet) results insignificant impacts. Finally, we also observe the transition zone between annular and periphery zone has a certain enhancing effect on the wall to bed heat transfer coefficient.

关键词： Spouted bed Two fluid model Kinetic theory of granular flow Supercritical CO_(2) Hydrodynamics Heat transfer

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Specific Heat Capacity and Coordination Number of Nano-Confined Transcritical Water

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Journal of Thermal Science 2025年第2期34卷 498-509页

作者： ZHANG Bowei JIANG Kun ZHANG Jie JIN Hui State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

In the field of nano energy,investigating the specific heat capacity and coordination number of nano-confined water is highly significant for gaining a better understanding of the energy and microstructure of confined *** this work,we employed the method of molecular dynamics(MD)simulation to calculate the specific heat capacity at constant volume and coordination number of water molecules confined in carbon nanotubes(CNTs)under different conditions(T=600-700 K,P=21.776 and 25 MPa,CNT diameter=0.949-5.017nm).The results showed that near the critical point,the specific heat capacity at constant volume of confined water was lower than that of bulk water,and the energy fluctuation showed a trend of first increasing and then remaining unchanged with the increase of temperature and CNT *** them,the saturation point of temperature is 650 K(reduced pressure P_(r)=1)and 660 K(P_(r)=1.15),and the saturation point of CNT diameter is 2.034 ***,the pseudo-critical temperature of confined water was the same as bulk water,and it increased with the increase of critical ***,with the increase of CNT diameter,the coordination number of confined water increased rapidly,and reaches the saturation state when the CNT diameter is 2.034 *** investigation revealed the mass and energy characteristics of nano-confined water near the critical point,which could provide guidance for the critical phase transition of nano-confined water.

关键词： molecular dynamics nano-confined transcritical water specific heat capacity at constant volume coordination number

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Co-production of hydrogen, oxygen, and electricity via an integrated solar-driven system with decoupled water electrolyzer and Na-Zn ion battery

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Journal of Energy Chemistry 2025年第1期100卷 621-627页

作者： Fei Lv Longjie Liu Jiazhe Wu Pengfei Wang Lixia Pan Dengwei Jing Yubin Chen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049ShaanxiChina

Combining water electrolysis and rechargeable battery technologies into a single system holds great promise for the co-production of hydrogen (H_(2)) and ***,the design and development of such systems is still in its ***,an integrated hydrogen-oxygen (O_(2))-electricity co-production system featuring a bipolar membrane-assisted decoupled electrolyzer and a Na-Zn ion battery was established with sodium nickelhexacyanoferrate (NaNiHCF) and Zn^(2+)/Zn as dual redox *** decoupled electrolyzer enables to produce H_(2)and O_(2)in different time and space with almost 100%Faradaic efficiency at 100 mA cm^(-2).Then,the charged NaNiHCF and Zn electrodes after the electrolysis processes formed a Na-Zn ion battery,which can generate electricity with an average cell voltage of 1.75 V at 10 m A cm^(-2).By connecting Si photovoltaics with the modular electrochemical device,a well-matched solar driven system was built to convert the intermittent solar energy into hydrogen and electric energy with a solar to hydrogen-electricity efficiency of 16.7%,demonstrating the flexible storage and conversion of renewables.

关键词： Hydrogen Electricity Decoupled water electrolyzer Na-Zn ion battery Solar energy

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Photothermally enhanced electrocatalytic water splitting with iron-doped nickel phosphide

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Journal of Energy Chemistry 2025年第3期102卷 243-252页

作者： Rui Zhao Chunyang Zhang Liting Wei Yan Zhang Daixing Wei Jinzhan Su Liejin Guo International Research Center for Renewable Energy(IRCRE) State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049ShaanxiChina

Although electrocatalytic water splitting holds significant promise for hydrogen production,unfavorable reaction energy barriers and kinetic properties lead to unsatisfactory conversion ***,we provide an innovative strategy to optimize the electrochemical activity of the Fe/Ni_(2)P catalyst through near-infrared(NIR)-induced photothermal *** Fe/Ni_(2)P-NIR yields a current density of 10 mA cm^(-2)at ultralow overpotentials of 16 mV for the hydrogen evolution reaction(HER)and 167 mV for the oxygen evolution reaction(OER),with Tafel slopes of 38.7 and 46.2 mV dec^(-1),*** bifunctional catalyst also delivers 10 mA cm^(-2)at a low voltage of 1.40 V for overall water *** NIR photoinduced local thermal effect activates abundant catalytic sites,accelerates charge and mass transfer,and improves intrinsic reaction *** by density functional theory(DFT)calculations,the photothermal effect reduces the energy barriers of the rate-determining steps(RDS)for^(*)H desorption on Fe/Ni_(2)P during HER and^(*)O formation on its reconstructed active phase NiFeOOH during *** realized photothermal-electrochemical integration with Fe/Ni_(2)P-NIR in an anion exchange membrane(AEM)electrolyzer,attaining 500 mA cm^(-2)at 1.76 V,with excellent stability over 50 *** strategy may significantly advance energy conversion technology towards economic hydrogen production through water electrolysis.

关键词： Photothermal effect Electrocatalytic overall water splitting Fe-doped Ni_(2)P Integrated energy conversion system Alkaline AEM electrolyzer

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Optimizing photothermal CO_(2) reduction through integrated band division utilization and thermal management structure

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Nano Research 2025年第2期18卷 227-234页

作者： Xue Ding Wenhao Jing Guiwei He Zhongjian Jiang Feng Wang Ya Liu Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase FlowXi’an Jiaotong UniversityXi’an 710049China

Solar-driven photothermal catalytic CO_(2) conversion into fuels offers a promising approach to reducing fossil fuel *** enhance the efficiency of photothermal CO_(2) reduction,photothermal catalyst design must not only sustain the high temperatures required for the reaction but also effectively utilize the entire solar *** this study,we present a novel photothermal catalyst architecture BiVO_(4)/Bi/BiOCl that surpasses traditional designs by integrating plasmonic metal Bi as the“hot spot”and BiOCl as the thermal insulation layer on the outermost *** structure realizes thermal management,contributing to maintaining the high temperatures required for the *** BiVO_(4)/Bi/BiOCl multi-component system synergistically absorbs the full solar light spectrum and achieves band-division utilization:short-and mid-wavelengths drive reduction and oxidation reactions,respectively,while long-wavelengths induce the photothermal *** BiVO4/Bi/BiOCl catalyst demonstrates high-efficiency CO_(2) conversion performance in an outdoor concentrating system,achieving a CO production rate of 9.5μmol/*** work presents a design strategy for functional photothermal catalysts,making them viable candidates for industrial-scale CO_(2) conversion processes.

关键词： CO_(2)reduction full spectrum band-division utilization Z-scheme photothermal catalytic

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Enhancing the performance of proton-exchange membrane fuel cell by optimizing the hydrophobicity and porosity of cathode catalyst layer

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Science China(Technological Sciences) 2025年第3期68卷 72-81页

作者： Yan ZHANG Puping JIA Suyi YANG Jinzhan SU Liejin GUO International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringSchool of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an710049China

Appropriate hydrophobicity and porosity of the proton-exchange membrane fuel cell(PEMFC)cathode catalyst layer(CCL)are essential for efficient charge and mass *** this study,the effects of the CCL hydrophobicity and porosity on PEMFC performance were comprehensively *** to a normal CCL,a cathode hydrophobic duallayer catalyst structure(with a 2:1 Pt loading ratio between the inner and outer layers and 9.3%polytetrafluoroethylene(PTFE)in the outer layer)exhibited a 29.8%increase in power *** the tested pore-forming agents,ammonium bicarbonate(NH_4HCO_(3))was the most suitable because of its low pyrolysis *** maximum power density of the CCL with a porous structure(prepared with a Pt/C:NH_4HCO_(3)mass ratio of 1:3)was 38.3%higher than that of the normal *** simultaneously optimizing the pore structure and hydrophobicity of the CCL,the maximum power density of the cathode hydrophobic dual-layer CCL(DCL)with pores showed a 44.7%increase compared to that of the normal *** study demonstrates for the first time that simultaneously optimizing cathode porosity and hydrophobicity can enhance PEMFC performance.

关键词： proton-exchange membrane fuel cell cathode catalyst layer membrane electrode assemblies polytetrafluoroethylene pore-forming agent

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MOF-derived NiCo bimetallic cocatalyst for enhanced photocatalytic overall water splitting

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Chinese Chemical Letters 2025年第3期36卷 427-431页

作者： Liang Dong Jingkuo Qu Tuo Zhang Guanghui Zhu Ningning Ma Chang Zhao Yi Yuan Xiangjiu Guan Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049C

The development of stable and efficient non-noble metal cocatalysts has arisen as a promising yet challenging endeavor in the context of photocatalytic overall water *** this study,NiCo alloy cocatalysts were synthesized with nickel/cobalt metal organic framework(NiCo-MOF)as source of nickel and *** characterization results demonstrate the successful deposition of alloy cocatalysts onto the surface of SrTiO_(3).The prepared SrTiO_(3)loaded NiCo-alloy can generate hydrogen and oxygen in a stoichiometric ratio for photocatalytic overall water splitting,achieving an apparent quantum yield of 11.9%at 350±10 *** calculations indicate that the introduction of cobalt has a beneficial regulatory effect on the hydrogen evolution sites of Ni,reducing the free energy of H *** synergistic catalytic effect of bimetallic catalysts contributes to enhancing photocatalytic activity and *** study offers constructive insights for the development of high-efficiency and cost-effective cocatalyst systems.

关键词： Photocatalysis Overall water splitting Non-noble metals Alloy Cocatalyst

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Effects of methanol and its cracked gas on ammonia consumption and NOx emission under high pressure

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International Journal of Hydrogen Energy 2025年 136卷 491-500页

作者： Yin, Geyuan Shen, Shujie Zhan, Haochen Hu, Erjiang Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

The mole fraction profiles for NH3/syngas were measured at 5.0 MPa and different blending ratios and compared with NH3/methanol to understand the effects of methanol and its cracked gas on ammonia oxidation and micro-species behavior. A kinetic model proposed in our previous work is validated against the measured data. The model demonstrates remarkable accuracy in predicting the concentration profiles of NH3 and NOx under all conditions. Moreover, a superior performance of methanol control is found at low temperatures, while syngas has a better performance at high temperatures. The onset temperature of methanol is lower than that of syngas. When the temperature reaches 950 K, H2 can provide more active OH than methanol and accelerate the ammonia consumption through the reaction cycle. Moreover, methanol triggers NO formation at 50 K lower than syngas, and the peak molar concentration of NO is lower than that of syngas at high blending ratios. At a substitution ratio of 50 %, NO generated by an ammonia-methanol mixture exhibits an "N"-shaped trend, while it monotonically increases with temperature with syngas blending. The peak concentrations of N2O with methanol are higher than those from syngas, especially at substitution ratios of 10 % and 25 %. © 2025 Hydrogen Energy Publications LLC

关键词： Nitrogen oxides

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Motion of a rigid particle in the lid-driven cavity flow

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Chinese Physics B 2025年第3期34卷 448-459页

作者： Fan Yang Zhe Yan Wencan Wang Ren Shi School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were *** computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit *** initial orientation of the particle has a minimal impact on both stages of *** contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release ***,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.

关键词： lattice Boltzmann methods immersed boundary method elliptical rigid particle lid-driven cavity flow

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Influence of internal components on gas-solid flow characteristics in fluidized bed reactor for organic silicon monomer synthesis

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Particuology 2025年第1期96卷 294-311页

作者： Xiaohan Guo Fei Gao Xuehui Xu Jianbo Zhao Yinghou Li Guanghui Chen Pan Zhang Key Laboratory of Multiphase Flow Reaction and Separation Engineering of Shandong Province College of Chemical EngineeringQingdao University of Science and TechnologyQingdao266042China College of Electromechanical Engineering Qingdao University of Science and TechnologyQingdao266043China

Internal components play a crucial role in the synthesis of organic silicon monomer in gas-solid fluidized bed reactors (FBRs). Finger-tube (F-tube) and U-tube components are commonly utilized to control the temperature and ensure its homogeneity in FBRs, thereby guaranteeing a high selectivity of the target product. The main objective of this work is to better understand the influence of F-tube and U-tube on the hydrodynamics in FBRs. Computational fluid dynamics (CFD) combined with the particle image velocimetry (PIV) technique were employed to explore the flow characteristics. The numerical data were validated against the particle velocity using an image processing technique. The results revealed that the F-tube increases the bed voidage by 3.2% and reduces the pressure drop by 13.0%. While the U-tube increases the bed voidage by 2.1% and reduces the pressure drop by 11.2%. These internals improve fluidization by ensuring even particle distribution and enhancing intra-particle circulation compared to reactors without internals.

关键词： Internal components Gas-solid fluidized bed reactors Fluid dynamics Particle image velocimetry system

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