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Novel Catalyst Coatings on Gas Diffusion Layers for Improved Proton Exchange Membrane Water Electrolysis: A Microscopic Analysis of D-Orbital Electron Interactions in Co0.75Ru0.21Ir0.04O0.9

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SSRN 2024年

作者： Wang, Weiding Wang, Hao Zhang, Yan Yang, Suyi Wang, Baoyuan Dong, Wenxuan Li, Lubing Zhang, Lei Su, Jinzhan Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an710049 China

Proton exchange membrane water electrolysis (PEMWE) has emerged as a reliable water splitting technology in recent years. The oxygen evolution reaction (OER) at the anode, is the rate-determining step in water electrolysis, and therefore, the kinetic and mass transfer performance of the oxygen evolution reaction should be further studied. Efficient electron and water transfer between the catalyst layer (CL) and gas diffusion layer (GDL) is crucial for optimizing PEMWE performance. In this work, Ru-core modified materials were successfully synthesized via a hydrothermal method and then spray-coated onto the surface of the gas diffusion layer. Physical and electrochemical characterization showed that 0.10 mg cm-2 was the optimal dosage of the coating. The single cell with this optimal coating exhibited a well-promoted and outstanding performance that a cell voltage of 1.71 V@1 A cm-2 and an overpotential of 222 mV@10 mA cm-2. This enhancement was primarily attributed to the improved ohmic and mass transfer properties. Specifically, the promotion of kinetic and mass transfer performance was due to the attraction of the empty d-orbitals of Ru, Co, and Ir, which enhanced electron transmission between the catalyst layer (CL) and gas diffusion layer. Physical analysis revealed that the reductive gaseous products caused Co (Ⅲ) to transform to Co (Ⅱ) and the formation of Co3O4 and RuO2 was well-protected by the Co (II)-rich Co3O4 phase due to its reductivity nature. Additionally, the effusion of gaseous products from the solid phase accelerated pore formation, thereby increasing the specific surface area of the material. © 2024, The Authors. All rights reserved.

关键词： Electrolysis

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Dynamic Characteristic Analysis of Sco2 Brayton Cycle Under Different Turbine Back Pressure Modes

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SSRN 2023年

作者： Zhao, Quanbin Xu, Jia yuan Hou, Min Zhang, Dalin Chong, Daotong Wang, Jinshi Chen, Weixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Closed supercritical carbon dioxide Brayton cycle has the advantages of high efficiency and high compactness. The compact structure and completely closed loop with supercritical state makes the dynamic characteristic different from that of steam Rankin cycle. This paper mainly focuses on the dynamic character of SCO2 cycle with different disturbance. Firstly, the dynamic characteristic of isolated heat exchangers is investigated under different disturbances. The response time of HTR and LTR is about 70 seconds, which is much longer than others. Then dynamic characteristics of SCO2 cycle are investigated with different turbine back pressure modes. Under cooled water flow rate disturbance, the operation parameter fluctuation amplitude and the response time with normal back pressure mode are slightly larger than those under fixed back pressure modes, and the effect of pressure iteration is not remarkable when cold water disturbance amplitude is small. But when water flow rate decreases 30%, the discrepancy becomes large and the tendency becomes opposite. Under heat fluoride flow rate disturbance conditions, the parameters iteration in closed loop restrain the non-coordinative of SCO2 pressure and temperatures. © 2023, The Authors. All rights reserved.

关键词： Brayton cycle

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CO2 Emission Characteristics Modeling and Low-Carbon Scheduling of Coal-Fired power Units Under Peak Shaving Conditions

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SSRN 2023年

作者： Yuan, Rongsheng Liu, Ming Chen, Weixiong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

To accommodate the high penetration of renewable power, the operational flexibility of coal-fired power units is highly required by the power system, so coal-fired power units frequently operate under peak shaving conditions. The CO2 emission characteristics of a coal-fired power unit are significantly influenced by the load factor, and also by unit capacity and many other design parameters. Therefore, detailed CO2 emission characteristics of a coal-fired power unit should be modeled and considered in the low-carbon scheduling of coal-fired power units under peak shaving conditions. In this study, coal-fired power units are classified by live steam parameters, unit capacity, reheat stages, cooling mode, and operation mode, and the models of detailed CO2 emission characteristics are developed and validated. An indicator is defined and modeled to evaluate the CO2 emission reduction rate of a coal-fired power unit considering the renewable power accommodation, and an optimization method for low-carbon scheduling is proposed. The proposed optimization method reduces the computational time by ~80%. Finally, a reference case study, including zero, current, and 2030 renewable power accommodation scenarios, is conducted. Results show that the marginal carbon emission of the power system decreases by 123.33 g/kWh in the 2030 renewable power accommodation scenario. © 2023, The Authors. All rights reserved.

关键词： Carbon

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Cooperative structure of Li/Ni mixing and stacking faults for achieving high-capacity Co-free Li-rich oxides

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Journal of Energy Chemistry 2024年第8期95卷 315-324,I0007页

作者： Zhen Wu Yu-Han Zhang Hao Wang Zewen Liu Xudong Zhang Xin Dai Kunyang Zou Xiaoming Lou Xuechen Hu Lijing Ma Yan Liu Yongning Liu State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049ShaanxiChina Qingdao Industrial Energy Storage Research Institute Qingdao Institute of Bioenergy and Bioprocess TechnologyChinese Academy of SciencesQingdao 266101ShandongChina Hefei Advanced Computing Center Operation Management Corp Ltd Hefei 230088AnhuiChina Center for High Performance Computing Network Information CenterXi’an Jiaotong UniversityXi’an 710049ShaanxiChina Wuhan Dongfeng Motor Corporation Ltd Wuhan 430056HubeiChina School of Materials Science and Intelligent Engineering Nanjing UniversitySuzhou 215163JiangsuChina Key Laboratory of MEMS of the Ministry of Education Southeast UniversityNanjing 210096JiangsuChina International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049ShaanxiChina

Co-free Li-rich layered oxides(LLOs)are emerging as promising cathode materials for Li-ion batteries due to their low cost and high ***,they commonly face severe structural instability and poor electrochemical activity,leading to diminished capacity and voltage ***,we introduce a Co-free LLO,Li_(1.167)Ni_(0.222)Mn_(0.611)O_(2)(Cf-L1),which features a cooperative structure of Li/Ni mixing and stacking *** structure regulates the crystal and electronic structures,resulting in a higher discharge capacity of 300.6 mA h g^(-1)and enhanced rate capability compared to the typical Co-free LLO,Li_(1.2)Ni_(0.2)Mn_(0.6)O_(2)(Cf-Ls).Density functional theory(DFT)indicates that Li/Ni mixing in LLOs leads to increased Li-O-Li configurations and higher anionic redox activities,while stacking faults further optimize the electronic interactions of transition metal(TM)3d and non-bonding O 2p ***,stacking faults accommodate lattice strain,improving electrochemical reversibility during charge/discharge cycles,as demonstrated by the in situ XRD of Cf-L1 showing less lattice evolution than *** study offers a structured approach to developing Co-free LLOs with enhanced capacity,voltage,rate capability,and cyclability,significantly impacting the advancement of the next-generation Li-ion batteries.

关键词： Co-free Li-rich oxides Li/Ni mixing Stacking faults Electronic structure

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A Numerical Study on Convective Condensation of Flue Gas in Tubular Heat Exchangers

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SSRN 2023年

作者： Yang, Kaixuan Yang, Jiahui Da, Yaodong Han, Lei Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

Accurate calculation of heat transfer process in condensing heat exchanger plays a crucial role in the waste heat recovery. In this study, the convective-condensation heat transfer process in a condensing heat exchanger with five small heat exchangers is analyzed through utilizing a new numerical simulation model. The method that loads the latent heat of vaporization as heat generation rate is adopted. Under the two working conditions in this study, the deviations of outlet temperature between numerical and experimental results are 1.3 and 2.2 K, respectively, while the deviations of total condensate water flow are 8.5% and 5.5%, respectively. Under the drier working condition, the average temperature reduction per row of tubes in the first small heat exchanger where is no condensation is significantly higher than that in the third small heat exchanger where vapor starts to condense, 5.8 and 2.6 K, separately. It indicates that the release of latent heat of vaporization slows down the cooling rate of the flue gas. In the small heat exchanger where vapor starts to condense, the amount of condensate water on the wall of each row of tubes increases first and then decreases slowly along the flow direction of flue gas. © 2023, The Authors. All rights reserved.

关键词： Heat exchangers

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Experimental Investigation of the Photovoltaic Thermal (Pvt) Integrated with Ground Heat Exchanger (Ghe) Using Volcanic Tuff Stones

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SSRN 2024年

作者： Alqatamin, Ahmad Jinzhan, S.U. International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

This study investigates the combination of photovoltaic thermal (PVT) and ground heat exchanger (GHE) using volcanic tuff stones as a heat storage material if the combination of PVT and GHE technologies provides the potential for energy generation increased efficiency and performance. Volcanic tuff stones known for their high thermal conductivity and heat retention, act as an effective means of heat exchange in the system. The objective of the study is to investigate the electrical, thermal performance and efficiency of this integrated system. Where the ground heat exchanger comprises a single hole filled with volcanic tuff stones arranged strategically, featuring gaps between them to facilitate heat exchange. The hole dimensions are specified as 2.5 meters in length, 2 meters in width, and 3 meters in depth. A fan is situated at the exit square duct (400*400 mm) to extract ambient air. Experimental data was collected from the PVT-GHE system to evaluate its efficiency in harnessing solar energy and providing space heating or other heating applications and compared it with a traditional PVT system. The results show that integrating GHE into PVT systems dramatically decreases solar cell temperature and improves electrical efficiency. A PVT system with GHE had the maximum electrical efficiency at 17.99%, compared to 17.52% in a PVT system without GHE. In addition, the greatest possible electrical power in a PVT system with GHE was 65 W, but in a PVT system without GHE, it was 61W. Also, the outlet air temperature from GHE was consistently higher than the ambient temperature throughout the days of the experiment, with an average difference of about 10 ºC. © 2024, The Authors. All rights reserved.

关键词： Solar energy

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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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Numerical Simulation of Fluid-Particle Flow of Jet in Supercritical Water Environment

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SSRN 2023年

作者： Zhang, Chuan Shang, Yuqi Su, Haozhe Ge, Zhiwei Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Supercritical water gasification provides a new approach to the green transformation of coal. Nevertheless, the flow behaviour of the fluid and particles inject into the reactor through the nozzle still warrant further research. In this paper, a three-dimensional numerical simulation of the particle jet in supercritical water environment is carried out using LES-DPM. The simulations focus on the effects of particle size, Stokes number, mass flux ratio and fluid initial velocity on the flow characteristics of the fluid-solid flow. The findings were that as the particle size decreases and the initial fluid velocity increases, the evolution of vortex structures became increasingly fierce, such as the destruction of large-scale coherent structures, the disappearance of vortex ribs, and the lateral expansion of vortices in the development section. Particle distribution exhibited characteristics similar to the vortex structure due to particles stuck closely with the carrier fluid when Stokes number is small (St1), the particles were freer from fluid interference and kept their original motion state moving forward. The fluid velocity at the center of the transverse interface jet decreased with increased mass flow ratio. © 2023, The Authors. All rights reserved.

关键词： Vortex flow

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Experimental Study on Boiling Heat Transfer Characteristics in Helical Coils with Large Coiled Diameters

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SSRN 2024年

作者： Shi, Yanggen Wu, Zhiyuan Li, Kepiao Zhang, Kui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

The boiling heat transfer characteristics in helical coils were investigated by experimental study. Experimental results indicated that the distribution of wall temperature trended to be more uniform due to weakened influence of centrifugal force and gravity force when the bulk fluid is closed to saturation temperature. Increase in heat flux decreases the quality of ONB (onset of nucleate boiling) while increase in mass flux delay ONB. The heat transfer was dominated by nucleate boiling with quality range of 00.6 in saturated boiling region. The quality of dryou decreases with the increase of pressure and it’s scarcely affected by heat flux. Dryout rends to occur at lower quality with the increase of heat flux at high pressure since redeposition rate decreases at higher pressure and entrainment rate increases due to higher heat flux © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Experimental Study on the Plate-Type Fuel Melting Behaviors Based on Alternative Materials

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SSRN 2024年

作者： Wu, Zhiyuan Li, Kepiao Zhang, Kui Chen, Ronghua Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

In this paper, low-temperature experiments are carried out on the visualized experimental device to study the melting behavior of plate-type fuel in severe accidents of the reactor. In the experiments, the plate-type fuel with different sizes made of nickel-chromium alloy, zinc and aluminum was used to carry out the visualized experiments in air, argon, and vacuum environment. It was found that both the size of the plate and the experimental environment have a significant influence on the melting behavior in this study. And the temperature distribution, melting behavior characteristic, the key parameters such as foaming position, foaming size, breaking position and breaking size were also obtained. Based on the experimental data, the physical phenomena and processes related to the blistering and melting of the fuel plates are analyzed in this paper, which provides experimental data support for the development of analysis model and formulating perfect mitigation strategies for severe accidents. © 2024, The Authors. All rights reserved.

关键词： Melting

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