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Experimental and simulation study of H 2 crossover in PEM water electrolysis for high-pressure hydrogen production up to 20 MPa

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International Journal of Hydrogen Energy 2025年 135卷 499-506页

作者： Jiazhe Wu Guoao Zhang Boyu Dong Yuhao Chang Yubin Chen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi 710049 P. R. China

High-pressure proton exchange membrane (PEM) water electrolysis offers considerable advantages, particularly in enabling direct integration with hydrogen storage and transportation systems while eliminating the need for external mechanical compressors. However, H 2 crossover is a bottleneck that induces high H 2 -in-O 2 content and low overall efficiency during high-pressure PEM water electrolysis. This study investigates H 2 crossover in PEM water electrolysis by combining in situ measurements and numerical simulations over a differential pressure range of 0–20 MPa. A linear correlation was observed between hydrogen crossover and current density within the range of 0–1 A cm −2 . The cathodic hydrogen mass transfer coefficient was determined to range from 1.6 to 3.2 mm s −1 , and the hydrogen solubility was estimated as 1.1 × 10 −3 mmol m −3 Pa −1 . The results highlight the importance of optimizing mass transfer and reducing hydrogen solubility within the cathode catalyst layer to mitigate H 2 crossover during high-pressure PEM water electrolysis.

关键词： High-pressure hydrogen Hydrogen crossover Proton exchange membrane Water electrolysis

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Experimental Study on Heat Transfer Characteristics of Supercritical Carbon Dioxide in a Vertical Circular Tube

SSRN

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SSRN 2025年

作者： Yang, Haikuo Nie, Ruishan Zhang, Kui Tian, Wenxi State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Supercritical carbon dioxide (S-CO2) nuclear energy and power systems have garnered significant attention for flow and heat transfer experiments because of their compact design, advanced circulation methods, and high thermal efficiency, aligning with future trends in nuclear power plant development. However, the dramatic change in physical properties of S-CO2 near its pseudo-critical point can lead to heat transfer deterioration (HTD) in heat exchangers, potentially damaging the S-CO2 Brayton system. This paper presents an experimental study on the HTD of S-CO2 in a vertical circular tube under forced circulation, examining how heat flux, inlet temperature, and system pressure influence *** analysis delves into the mechanisms of HTD, focusing on the buoyancy and flow acceleration effects. Additionally, the study explores the impact of heat flux and system pressure on S-CO2 natural circulation. Ultimately, the research summarizes the flow and heat transfer characteristics of S-CO2 and proposes a new heat transfer correlation formula, demonstrating an error margin within ±25%, which meets practical engineering requirements. This experimental study contributes valuable data to the understanding of flow and heat transfer phenomena in S-CO2, offering significant insights for future applications. © 2025, The Authors. All rights reserved.

关键词： Nuclear energy

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Toward the influence of fluid convection on filtered drag force in fluidized gas-particle flows

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Powder Technology 2025年 460卷

作者： Jiang, Ju Yuan, Shouzheng Chen, Xiao Yang, Bolun Zhou, Qiang School of Chemical Engineering and Technology Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Mesoscale drag modeling for gas-solid flows is typically based on fully-periodic systems where fluid convection is insignificant. This study examines a series of 2D sudden-expanded fluidized beds (SEFBs) to investigate the effects of fluid convection on the filtered drag force. A priori analysis indicates that the volumetric force induced by convection has a notable impact on the filtered drag force, and correlations of drag force using traditional markers (such as solid volume fraction, slip velocity, and filter size) fail to provide accurate predictions. In contrast, the gas-phase pressure gradient shows a good correlation with drag force when strong convection is present. Posterior tests in the SEFBs with several existing drag models reveal that the predictive capacity of drag models constructed with traditional markers declines under conditions with strong convection, whereas the drag model incorporating the gas-phase pressure gradient still performs well. © 2025 Elsevier B.V.

关键词： Drag coefficient

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Electrochemical evolution of a metal oxyhydroxide surface on two-dimensional layered metal phosphorus trisulfides enables the oxidation of amine to nitrile

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Carbon Energy 2025年第3期7卷 133-147页

作者： Binglan Wu Karim Harrath Marshet Getaye Sendeku Tofik Ahmed Shifa Yuxin Huang Jing Tai Fekadu Tsegaye Dajan Kassa Belay Ibrahim Xueying Zhan Zhenxing Wang Elisa Moretti Ying Yang Fengmei Wang Alberto Vomiero State Key Laboratory of Chemical Resource Engineering College of ChemistryBeijing University of Chemical TechnologyBeijingChina CAS Key Laboratory of Nanosystem and Hierarchical Fabrication National Center for Nanoscience and Technology(NCNST)BeijingChina Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of EducationCollege of Chemistry&Materials ScienceNorthwest UniversityXi'anChina State Key Laboratory of Multiphase Flow in Power Engineering International Research Center for Renewable EnergyXi'an Jiaotong UniversityShaanxiChina Fundamental Science Center of Rare Earths Ganjiang Innovation AcademyChinese Academy of ScienceGanzhouChina Ocean Hydrogen Energy R&D Center Research Institute of Tsinghua University in ShenzhenShenzhenChina Department of Molecular Sciences and Nanosystems Ca'Foscari University of VeniceVenezia MestreItaly Testing and Analysis Center Institute of Chemistry Chinese Academy of SciencesBeijingChina Department of Engineering Sciences and Mathematics Division of Materials ScienceLuleåUniversity of TechnologyLuleåSweden

Selective oxidation of amines to imines through electrocatalysis is an attractive and efficient way for the chemical industry to produce nitrile compounds,but it is limited by the difficulty of designing efficient catalysts and lack of understanding the mechanism of ***,we demonstrate a novel strategy by generation of oxyhydroxide layers on two-dimensional iron-doped layered nickel phosphorus trisulfides(Ni1-xFexPS_(3))during the oxidation of benzylamine(BA).In-depth structural and surface chemical characterizations during the electrocatalytic process combined with theoretical calculations reveal that Ni(1-x)FexPS_(3) undergoes surface reconstruction under alkaline conditions to form the metal oxyhydroxide/phosphorus trichalcogenide(NiFeOOH/Ni1-xFexPS_(3))***,the generated heterointerface facilitates BA oxidation with a low onset potential of 1.39 V and Faradaic efficiency of 53%for benzonitrile(BN)*** calculations further indicate that the as-formed NiFeOOH/Ni1-xFexPS_(3) heterostructure could offer optimum free energy for BA adsorption and BN desorption,resulting in promising BN synthesis.

关键词： 2D layered materials benzylamine oxidation metal phosphorus trichalcogenides surfacereconstructed heterostructure

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Effect of Surfactant Concentration on the Behavior of Single Oxygen Bubble in Photoelectrochemical Water Splitting

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Langmuir 2025年

作者： Yang, Zihan Xu, Qiang Luo, Xinyi Nie, Tengfei Li, Jinfeng Wang, Mengsha Guo, Liejin Jiangxi Provincial Key Laboratory of Particle Technology Jiangxi University of Science and Technology Ganzhou341000 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The control of bubble growth and departure during the process of photoelectrochemical water splitting is crucial for enhancing gas production efficiency. By introducing varying concentrations of surfactants into the electrolyte and using a synchronous measurement system, we examined how the change in surfactant concentration affects bubble nucleation and growth characteristics. The results indicate that bubbles’ critical nucleation potentials initially decrease and subsequently increase with increasing surfactant concentration, reaching a minimum value when the concentration is 1 × 10-7 M. In contrast, bubble growth periods and departure diameters reach their maximum values. Further analysis shows that the gas production rate and the average gas evolution efficiency reach their maximum when the surfactant concentration is 1 × 10-7 M, indicating that adding an appropriate amount of surfactant is advantageous for gas production. In addition, a force equilibrium model incorporating the Marangoni force at various surfactant concentrations was developed to predict oxygen bubbles’ departure diameter. The predicted values exhibit excellent concurrence with the experimental data. The solutal Marangoni force is the primary determinant that affects bubble departure diameter when the surfactant concentrations are below approximately 4 × 10-6 M, while the thermal Marangoni force assumes precedence when concentrations exceed about 4 × 10-6 M. © 2025 American Chemical Society.

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Experimental study on heat transfer deterioration and critical heat flux of DNB type in helically coiled tubes

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International Journal of Thermal Sciences 2025年 215卷

作者： Chang, Fucheng Lou, Jiacheng Wu, Xiaoyi Li, Shuai Yang, Jiaqi Li, Xi Li, Huixiong National Key Lab of Aerospace Power System and Plasma Technology School of Mechanical Engineering Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

Helically coiled tubes (HCTs) are extensively utilized in numerous engineering fields due to their exceptional heat transfer and structural capabilities. The thermal safety within HCTs is crucial for the long-term stable operation of heat transfer systems. The heat transfer deterioration and critical heat flux (CHF) of departure from nucleate boiling (DNB) type in the HCTs at subcritical pressure were experimentally studied in this paper. The special circumferential wall temperature distribution was obtained and the effects of inlet cooling, pressure, mass velocity and HCT orientation on CHF were investigated. As the inlet subcooling increased, the CHF increased almost linearly. As the mass velocity increased, the turbulence degree in the HCT increases significantly, bubbles were less likely to merge and accumulate, and the CHF increased substantially. It was found that the CHF in the vertical HCT was higher than that in the horizontal HCT under the same working conditions because of the combined action of gravity and centrifugal force. The CHFv/CHFh exhibits a reduction with elevated inlet subcooling and pressure, and the influence of mass velocity on CHFv/CHFh is related to the pressure. New orientation-specific CHF correlations for vertical and horizontal HCTs are developed, achieving high prediction accuracy across pressures of 16–20 MPa and mass fluxes of 320–560 kg m−2 s−1. These findings can provide theoretical support for the optimization design and safe operation of the HCT heat transfer systems. © 2025

关键词： Thermal engineering

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Prediction of acoustic agglomeration enhanced by solid seed particles using the DSMC method

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Advanced Powder Technology 2025年第6期36卷

作者： Su, Junxu Wu, Zhihao Fan, Fengxian Hu, Xiaohong Su, Mingxu School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

Acoustic agglomeration enhanced by large-sized solid seed particles is investigated using the direct simulation Monte Carlo (DSMC) method. The process of acoustic agglomeration is revealed in terms of temporal evolution of velocities, diameters, and number weights of simulated particles, as well as normalized concentration and average diameter of small particles. Furthermore, the enhancement of acoustic agglomeration by the solid seed particles is evaluated at varying parameters. The results show that the agglomeration performance is enhanced within a shorter residence time when the solid seed particles are present. Increasing acoustic intensity or solid seed particle concentration leads to more efficient acoustic agglomeration, while the acoustic frequency, particularly beyond 2 kHz, has little effect on agglomeration performance. Moreover, a noticeable increase in agglomeration efficiency is observed when the seed particle diameter increases from 20 to 40 µm. However, once it exceeds 40 µm, the increase in agglomeration efficiency diminishes. © 2025 The Society of Powder Technology Japan.

关键词： Agglomeration

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Molecular dynamics study on bubble nucleation characteristics on rectangular Nano-Grooved surfaces

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Journal of Molecular Liquids 2025年 420卷

作者： Li, Zhibin Lou, Jiacheng Wu, Xiaoyi Li, Xujun Chang, Fucheng Wang, Hengyuan Li, Huixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China National Key Lab of Aerospace Power System and Plasma Technology School of Mechanical Engineering Xi'an Jiaotong University Xi'an710049 China

The micro/nanoscale structures on metal surfaces are of significant research interest for boiling heat transfer and exhibit great application potential in the thermal management of high-power electronic devices. This study employs the molecular dynamics simulation method to investigate the boiling heat transfer characteristics of hydrophilic rectangular shallow nano-groove structures, comparing them with the smooth surface. The phase transition heat transfer characteristics of liquid films on the smooth surface, single rectangular groove (SRG) surface, and overlapping rectangular groove (ORG) surface are revealed by analyzing the variations of parameters such as energy contour diagrams, bubble volume, liquid film temperature, and average potential energy. The research results indicate that water molecules are in a solid-like state within shallow grooves, while the nucleation sites of initial bubbles form randomly outside the grooves. During the initial heating and bubble growth, the initial nucleation time and bubble growth rate of ORG are slower than those of SRG, due to the small rectangular groove on ORG that diminishes the energy transfer efficiency. During bubble formation and growth, the average kinetic energy within the liquid film fluctuates at the nucleation moment in the critical nucleation region, and the average potential energy rises from −0.083 eV. These findings provide a theoretical basis for the micro/nanoscale structure design of vapor-liquid phase transition thermal management devices. © 2024 Elsevier B.V.

关键词： Kinetic energy

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Operational flexibility enhancement of a combined heat and power plant supplying industrial steam: The integration of sensible or sensible-latent heat storage system

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Journal of Energy Storage 2025年 117卷

作者： Tang, Haiyu Liu, Ming Zhang, Kezhen Wang, Chaoyang Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Xi'an Thermal Power Research Institute Co. Ltd. Xi'an710054 China

The increasing penetration of renewable energy requires greater operational flexibility of thermal power plants, as dispatchable power sources are essential to balance the power supply and demand sides. However, the CHP plant has restricted load cycling range due to its heat dominated operation mode. The Integration of a high-temperature heat storage system is a potential solution to enhance the operational flexibility of the CHP plant that cogenerates industrial steam and power. However, the optimal design of the heat storage system integrated within a CHP plant is complicated due to the changing operation conditions and various heat exchanging mediums. In this study, the design method of the sensible or sensible-latent heat storage system integrated with a CHP plant supplying industrial steam was proposed. The simulation, exergy analysis and economic analysis models were developed, and a case study of 350 MW CHP plant was conducted. The maximum CHP plant output power decrement is 13.59 MW when the heat of flue gas and main steam is stored in the sensible or sensible-latent heat storage system. The exergy-to-exergy efficiencies of sensible and sensible-latent heat storage systems are 71.60 % and 77.76 %, respectively. However, the economic analysis results show that the sensible heat storage system is more cost-effective than the sensible-latent heat storage system. © 2025 Elsevier Ltd

关键词： Latent heat

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Molecular dynamics revealing the non-monotonic variation of oil–water interfacial tension under the effect of cations and asphaltenes

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Journal of Molecular Liquids 2025年 431卷

作者： Zhang, Faxue Wen, Boyao Lu, Xi Wang, Haibo Luo, Zhengyuan Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China Petroleum Exploration and Production Research Institute of Sinopec Beijing China

The cations can significantly affect the interfacial dynamics of asphaltene molecules, which greatly change the mechanics of oil–water interfaces and thus have a remarkable impact on the chemical flooding process of heavy oil. However, Due to the weak amphiphilic property of asphaltene, the effects of cations on the interfacial behaviors of asphaltene as well as the interfacial mechanics are still unclear. Here, we study the effects of different types and concentrations of cations (Na+, Ca2+ and Mg2+) on the interfacial tension of oil–water systems with different asphaltenes (C5Pe) concentrations by using molecular dynamics simulations. As asphaltene concentration rises, the stronger interactions between cation and asphaltene induce an interfacial enrichment of asphaltenes, resulting in a decrease of interfacial tension. The cations have a more prominent impact on the interfacial tension when the oil–water interfaces reach supersaturated adsorption state of asphaltene molecules. The interfacial tension shows a non-monotonic variation with cation concentration increasing, which has a minimum at intermediate cation concentrations in our simulations. We explain this non-monotonic dependence of interfacial tension on cation concentration by a coupling effect of cations and asphaltene molecules. Under low cation concentrations, the interaction between cations and asphaltenes gradually enhances with cation concentration increasing, leading to a weaker π–π interaction between asphaltenes. Consequently, the asphaltene aggregates disperse and individual asphaltene molecules can easily migrate to the interface. The surface density of asphaltene thus increases, causing a reduction in interfacial tension. At high cation concentrations, cations strongly shield the electrostatic attraction between asphaltene and water molecules, so that the adsorption ability of asphaltenes at interface will weaken or even desorb, thus the interfacial tension elevate. Our results reveal the under

关键词： Adsorption Aggregation Asphaltenes Cations Interfacial tension Molecular dynamics

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