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Effects of physical properties of supercritical water on coarse graining of particle cluster

Particuology 2023年第11期82卷 166-178页

作者： Xiaoyu Li Huibo Wang Yi Li Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710049China

The coarse graining of particle cluster is of great significance to the study of a fluidized bed. The effects of variations in the physical properties of supercritical water on the coarse graining of particle cluster are investigated in this work. The drag coefficient distributions of the particle cluster are not influenced by the physical properties. However, the physical properties have effects on the values of drag coefficient. The effects of physical properties are weaker in the case of large particle concentrations. Furthermore, the physical properties lead to that the effect of particle cluster wake on the drag of downstream particles being significantly different from that of constant property flow. The variation trend of drag of coarse graining particle is consistent with that of isolated particle. The physical properties lead to significant differences in the values of drag. In this paper, the dominance of the effects of physical properties in a variety of cases is confirmed. Finally, a physical properties effect model is developed accordingly.

关键词： Supercritical water Variations in physical properties Fluidized bed Coarse grain method Particle drag

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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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Semiempirical equations of state of H_(2)O/CO_(2) binary mixtures in graphite nanoslits

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 83-92页

作者： Haoxuan Li Bin Zhao Chengzhen Sun Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The existence of confining walls limits the prediction accuracy of nanoconfined fluids using macroscopic equations of state(EOSs);moreover,appropriate EOSs for multicomponent mixture fluids in nanoconfined spaces are ***,we derive the EOS of multicomponent mixture fluids confined in nanospaces at high temperatures and pressures,mainly considering the nanoconfinement effect and the competitive adsorption effect between different ***,the EOSs are validated through comparison with the molecular dynamics-simulated Pv T data of CO_(2)/H_(2)O mixtures in graphite *** consider the above effects,we derive two EOSs via two modeling methods:EOS I is obtained through modification of the actual component occupation volume in the Peng-Robinson equation of state(PR EOS)by fitting the binary component interaction coefficient and the number of adsorbed molecules according to a selectivity coefficient,while EOS II is obtained by considering the decreased pressure of the fluids in PR EOS by adding an attractive term between components and *** the simulation results as a benchmark,the two EOSs exhibited good prediction accuracies under low CO_(2) concentrations,and generally,EOS II was more accurate than EOS *** study fills the gap in the EOSs of nanoconfined mixture fluids,and the obtained equations can help to further describe the thermodynamic properties of confined mixture fluids.

关键词： confined fluid mixtures equation of state nanoconfined spaces molecular dynamics simulation

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Numerical Investigation on the Heat Transfer Characteristics of Supercritical Water in a Non-Uniformly Heated Tube for a Supercritical CFB Boiler

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Journal of Thermal Science 2023年第5期32卷 1807-1818页

作者： DU Xiaocheng SONG Yuanyuan XIANG Yuxuan ZHOU Yanjun WANG Aoyu YANG Dong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical *** Shear Stress Transport(SST)k-ωmodel was adopted for describing *** operating parameters are chosen according to a 660 MW ultra-supercritical CFB *** heat transfer performances under different operating parameters,such as boiler load,flow direction and heat flux distribution are *** temperature and heat flux on inner wall varies along the circumference and show symmetric *** overall heat transfer performances at each cross section are better than the local heat transfer performance of midpoint of heating *** direction has a great influence on heat transfer performance;it changes the radial distribution of axial velocity and then affects the turbulence ***,upward flow condition shows a better heat transfer *** heat flux improves both the overall and local heat transfer *** the heat flux area is not conducive to the overall heat transfer,but does not affect the local heat transfer at the midpoint of heating ***,a new correlation is fitted based on the simulated results of supercritical water heat transfer with circumferential non-uniform heat flux distributions.

关键词： supercritical CFB boiler circumferential non-uniform heat flux numerical simulation heat transfer correlation

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Large Eddy Simulation Study on the Turbulence and Flame Characteristics under Analogical Integral Scale and Turbulence Intensity of Turbulent Premixed Flames

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Journal of Thermal Science 2023年第1期32卷 488-501页

作者： WEI Xutao WANG Jinhua ZHANG Meng HUANG Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Bunsen burner is a typical geometry for investigating the turbulence-flame *** most experimental studies,only turbulence intensity u′and integral scale l0 are used to characterize the turbulent flow field,regardless of the perforation geometry of perforated ***,since the geometry influences the developing process and vortex broken,the plate geometry has to be considered when discussing the flame-turbulence *** order to investigate conditions at the same l0 and u′using different geometries,large eddy simulation of CH_(4)/air flames with dynamic TF combustion model was *** model validation shows good agreement between Large Eddy Simulation(LES)and experimental *** the non-reacting flows,the Vortex Stretching of circular-perforated plate condition is always larger than that of slot-perforated plate condition,which comes from the stresses in the flow fields to stretch the vorticity *** reacting flows,at the root of the flame,the Vortex Stretching plays a major role,and the total vorticity here of circular-perforated plate condition is still larger(53.8%and 300%larger than that of the slot-perforated plate at x/D=0 and x/D=2.5,respectively).More small-scale vortex in circular-perforated plate condition can affect and wrinkle the flame front to increase the Probability Density Function(PDF)at large *** 3D curvature distributions of both cases bias to negative *** negative trend of curvatures at the instant flame front results from the Dilatation ***,the value of the Vortex Stretching and the Dilatation at the flame front of circular-perforated plate condition is obviously larger.

关键词： large eddy simulation integral scale turbulence intensity vorticity flame curvature

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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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Impact of bimetallic synergies on Mo-doping NiFeOOH:Insights into enhanced OER activity and reconstructed electronic structure

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Frontiers in Energy 2024年第6期18卷 850-862页

作者： Jingkuo Qu Yuchen Dong Tuo Zhang Chang Zhao Liting Wei Xiangjiu Guan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

NiFe(oxy)hydroxide(NiFeOOH)is recognized as a highly active non-precious metal catalyst in alkaline water electrolysis due to its exceptional catalytic *** this work,high valence molybdenum(Mo)is introduced to improve the electronic structure and enhance the electrical conductivity of NiFeOOH for oxygen evolution reaction(OER).The introduction of Mo results in a Mo-doped NiFeOOH catalyst with a significantly reduced overpotential of 205 mV at 10 mA/cm^(2)and a Tafel slope of 31.7 mV/dec,enabling stable operation for up to 170 *** empirical experiment and theory simulations are employed to gain insight into the 3d-electron interactions between molybdenum and nickel(Ni),iron(Fe)in Mo-doped *** results indicate that Mo-doping enhances the valence states of Ni and Fe,leading to a shift in the d-band center of the bimetallic active *** modification affects the transformation of Mo-doped NiFeOOH into theγ-NiFeOOH active *** potent combination lends credence to its potential suitability and utility in OER applications.

关键词： Mo doping NiFe(oxy)hydroxide(NiFeOOH) bimetallic synergies oxygen evolution reaction(OER) electronic structure

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Characterizations of gas-liquid interface distribution and slug evolution in a vertical pipe

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Petroleum Science 2023年第5期20卷 3157-3171页

作者： Hai-Yang Yu Qiang Xu Ye-Qi Cao Bo Huang Han-Xuan Wang Lie-Jin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi’an710049ShaanxiChina

Large vertical pipes are key structures connecting subsea wells to offshore ***,existing studies mainly focus on small vertical *** a vertical acrylic pipe with 80 mm inner diameter and 11 m height,a high-speed camera was used to visually research the influences of pipe diameters,liquid properties and inlet effect on air-water co-flow *** flow regime maps of vertical pipes(diameters are in the range of 50e189 mm)were compared and the critical gas velocity of the transition boundary from bubble to slug flow tended to increase with the increase of diameters at D≥80 ***-flux models were established in different flow regimes and liquid properties have a significant effect on drift coefficients of bubble flow and slug flow(void fraction a≤0.4).The influence of inlet turbulent effect on the gas-liquid interface distribution gradually weakened and disappeared from the pipe base to 85D,where the flow was fully *** frequency has a trend of increase first and then decrease with the gas Weber numbers increasing at low liquid superficial velocities(J_(L)≤0.31 m/s).And on the basis of this law,a new slug frequency correlation was *** was found that there was an exponential relationship between the ratio of lengths of Taylor bubble to slug and the void fraction.

关键词： Void fraction flow regime Drift coefficien Slug frequency Taylor bubble length

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Investigation on a Supercritical Water Gasification System with CO_(2)as Transporting Medium

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Journal of Thermal Science 2023年第4期32卷 1614-1625页

作者： WANG Weizuo LU Bingru SHI Jinwen ZHAO Qiuyang JIN Hui State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

As a benign energy vector,hydrogen has been discussed for a long *** water gasification was one of good ways to produce ***,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium *** plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was *** flow of H_(2)O input into the reactor was 1000 kg/*** typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:*** of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,*** system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.

关键词： phenolic plastics supercritical water gasification CO_(2)-transporting system energy and exergy flow

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Syngas production by photoreforming of formic acid with 2D V_(x)W_(1-x)N_(1.5) solid solution as an efficient cocatalyst

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Frontiers in Energy 2024年第5期18卷 640-649页

作者： Xiaoyuan Ye Yuchen Dong Ziying Zhang Wengao Zeng Bin Zhu Tuo Zhang Ze Gao Anna Dai Xiangjiu Guan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

Formic acid(FA)is a potential biomass resource of syngas with contents of carbon monoxide(CO,60 wt.%)and hydrogen(H_(2),4.4 wt.%).Among the technologies for FA conversion,the photoreforming of FA has received widespread attention due to its use of green solar energy conversion technology and mild reaction ***,a V-W bimetallic solid solution,V_(x)W_(1-x)N_(1.5) with efficient co-catalytic properties was first and facilely *** CdS was used as a photocatalyst,the activity performance of the V_(0.1)W_(0.9)N_(1.5) system was over 60%higher than that of the W_(2)N_(3) *** computational simulations and experiments showed the V_(0.1)W_(0.9)N_(1.5) had great metallic features and large work functions,contributing a faster photo-generated carrier transfer and less recombination,finally facilitating a great performance in cocatalyst for syngas production in photoreforming *** work provides an approach to synthesizing novel transition metal nitrides for photocatalysis.

关键词： photocatalysis syngas formic acid cocatalyst solid solution

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