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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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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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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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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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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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Lattice-mismatch-induced formation of defect-rich Pd-Cu alloy nanocages for enhanced formic acid oxidation activity

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Science China Chemistry 2025年第2期68卷 481-491页

作者： Zhaojun Liu Zhengyan Wang Zhaoyu Wang Hao Yuan Yuke Bai Xiaoxiao Wang Zerui Mu Chunxia Wu Kai Liu Zhun Hu Chuanbo Gao Sate Key Laboratory of Multiphase Flow in Power Engineering Frontier Institute of Science and TechnologyXi’an Jiaotong UniversityXi’an 710049China Institute of Industrial Catalysis School of Chemical Engineering and TechnologyXi’an Jiaotong UniversityXi’an 710049China

Crystallographic defects in noble metal nanocrystals are recognized as highly active catalytic sites,significantly enhancing activities in many important *** their importance,synthesizing noble metal nanocrystals with a high density of defects poses a considerable synthetic ***,we present a novel lattice mismatch-induced formation mechanism to create high-density defects in noble metal *** approach takes advantage of lattice mismatch to enable nonepitaxial nucleation and growth of a noble metal on a foreign metal substrate,forming abundant noble metal crystallites with random lattice orientations not dictated by the substrate *** these crystallites grow extensively,they merge,forming numerous grain boundaries and yielding defect-rich noble metal ***-rich alloy nanocrystals can also be synthesized through a subsequent vacancy-diffusion alloying *** take defective PdCu alloy nanocages as an example and demonstrate the effectiveness of crystallographic defects in enhancing catalytic performance of noble metal *** nanocages exhibit superior activity in the electrocatalytic formic acid oxidation reaction,which is 1.6 times greater than their defect-free *** strategy offers a new avenue for creating defect-rich noble metal nanocrystals as highly efficient catalysts for a wide array of catalytic applications.

关键词： noble metal nanocrystals defects non-epitaxial growth electrocatalysis formic acid oxidation reaction

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Performance and Sizes of sCO_(2)Multistage Axial Compressors at Various power Capacities

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Journal of Thermal Science 2025年第2期34卷 352-373页

作者： WANG Tianze XU Jinliang ZHENG Haonan QI Jianhui Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing100026China Key Laboratory of Power Station Energy Transfer Conversion and System(North China Electric Power University) Ministry of EducationBeijing102206China School of Energy and Power Engineering Shandong UniversityJi’nan250061China

The supercritical carbon dioxide(sCO_(2))cycle can be powered by traditional as well as clean *** help users obtain more accurate results than the literatures with pre-set compressor efficiency,we proposed a complete model to establish a link between the performance,sizes of compressors and parameters such as power W_(C),inlet temperature T_(in),inlet pressure P_(in)and pressure ratioε.Characteristic sizes of compressors l_(c),profile loss Y_(p)and clearance loss Ycl are all proportional to powers of W_(C)with powers of 0.5,-0.075 and-0.5 to 0 respectively;the scaling laws are constant in the range of capacities from 20 MW to 200 *** compressor isentropic efficiencyη_(tt)grows as the W_(C)increases,and the curves become *** efficiency improves over the full power range when the speed is changed from standard speed to the optimal speed;theη_(tt)curves turn soft as the n *** the P_(in)and T_(in)approach the critical point,theη_(tt)*** efficiency follows a parabolic curve as theεincreases,this parabolic distribution results from the tradeoff between the change in losses and the pressure distribution of ***η_(tt)versus P_(in),T_(in)andεrelations are similar at various capacities because of insignificant changes in the distribution of *** efficiency maps facilitate the estimation of system performance,while scaling law for irreversible losses and characteristic lengths,along with constant criterion analyses,aid in comprehending the characteristics of compressors across various capacities.

关键词： sCO_(2)cycle compressor efficiency irreversible losses scaling laws

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