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Atomic Insights into Hydrogen Peroxide Decomposition on the Surface of Pure and Pre-Treated Silver: A Reactive Molecular Dynamics Simulation Study

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SSRN 2023年

作者： Zhao, Xiao Feng, Yiming Zhang, Bowei Jin, Hui Wei, Xianggeng State Key Laboratory of Solid Propulsion Northwestern Polytechnical University Shaanxi Xi’an710072 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Based on ReaxFF molecular dynamics simulation, H2O2 decomposition on pure and pre-treated silver catalyst is studied at a microscopic level. The pretreatment undergoes a surface annealing with redundant H2O2 on top of catalyst. The simulation results indicate that H2O2 decomposition can be drastically accelerated by elevating temperature. The extent of decomposition is closely related to bond, hydrogen bond, and potential energy of simulation system. It is found that H2O2 decomposition follows a four-stage HO-OH bond break mechanism while it needs three times longer for pre-treated silver catalyst than pure silver catalyst. The activation energy of pre-treated silver catalyst is about 50% lower than pure silver catalyst. However, the overall reaction rate of pre-treated silver catalyst is about an order of magnitude slower than pure silver catalyst, which owes to the much smaller pre-factor. It is believed that although the pretreatment causes silver oxide to be formed on the surface, it leads to more hydrogen and oxygen atoms deposited so that most active sites for catalytic reaction are blocked for further decomposition. This may be helpful to understand the inherent mechanism of H2O2 decomposition on silver-based catalyst and provide instructional advice for further catalyst modification design. © 2023, The Authors. All rights reserved.

关键词： Catalysts

Study on the Safety Characteristics of Fluoride-Salt-Cooled High-Temperature Advanced Reactor

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SSRN 2023年

作者： Lv, Xindi Zhang, Dalin Li, Xinyu Zhou, Xingguang Jiang, Dianqiang Su, Guanghui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

FuSTAR is a small, modular fluoride-salt-cooled high-temperature advanced reactor, proposed by Xi'an Jiaotong University (XJTU), aiming at fulfilling the requirements of Gen IV nuclear system and meanwhile ensuring the inherent safety and economics. In order to evaluate the safety performance of FuSTAR, five typical design basis accidents are selected for safety analysis with different initial events. The sensitivity analysis is also performed. The results of transient accidents indicate that safety of FuSTAR has been guaranteed in URIA and ULOF. Meanwhile, the maximum limit of external parameters causing ULOHS and UOC are obtained by sensitivity analysis. In the ULOF and ULOHS, the peak of fuel temperature, cladding surface temperature and core outlet temperature of coolant are below their safety limits. Therefore, FuSTAR exhibits acceptable safety under design basis accidents. This study will provide supports in verifying the rationality of the design and the subsequent optimization of FuSTAR. © 2023, The Authors. All rights reserved.

关键词： Sensitivity analysis

Transient Thermoelectric Characteristics of the Principle Prototype for the Heat Pipe Cooled Nuclear Silent Themoelectirc Reactor (Nuster)

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SSRN 2023年

作者： Guo, Kailun Zhang, Yin Lin, Xingyang Huang, Jinlu Wang, Chenglong Qiu, Suizheng Tian, Wenxi Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy And Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

This paper proposes an optimized design for the Heat Pipe ThermoElectric Generator(HPTEG) principle prototype. The refined scheme adopts high-temperature sodium heat pipes as heat transfer elements to enhance the overall operating temperature of the device. It adopts Half-Hessler(HH) alloy ThermoElectric Generator(TEG) arranged on the upper and lower sides of the heat exchanger to enhance the thermoelectric conversion efficiency of the device. A heat pipe dynamic conduction model is established to simulate the start-up process of the sodium heat pipe. A TEG model is developed, which is able to simulate the three-dimensional thermoelectric properties of the TEG. The numerical simulation platform is used to analyze the steady-state and transient thermoelectric properties of the refined HPTEG prototype. This study provides data support for the subsequent design modification of the future HPTEG principle prototype and provides ideas for the 3D transient calculations of the solid-state heat pipe reactors. © 2023, The Authors. All rights reserved.

关键词： Heat pipes

Development of typical processes and key devices for direct air CO2 capture

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Meitan Xuebao/Journal of the China Coal Society 2024年第10期49卷 4203-4221页

作者： Yu, Binpeng Tan, Lei Wang, Ding Wang, Limin Xiang, Xiaofeng Wang, Zhichao Jin, Zhonghua Yang, Bolun Wu, Zhiqiang School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an710049 China Shaanxi Province Energy and Chemical Process Intensification Key Laboratory Xi’an710049 China School of Engery and Powerl Engineering Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an710049 China Shaanxi Engineering Research Center if Coal Fired Boiler Environmental Protection Xi’an710054 China

Conventional carbon capture and storage technologies and carbon capture, utilization and storage technologies mainly target CO2 emissions from fixed sources, while direct air capture CO2 (DAC) technology, as an emerging negative carbon emission technology, can capture CO2 emissions from distributed sources and further reduce the global atmospheric CO2 concentration. In this paper, the development process of DAC's typical liquid absorption process, solid adsorption process and the construction of relevant demonstration projects are introduced, the technical characteristics of emerging DAC processes are analyzed, and the key equipment schemes and future development trends of existing DAC processes are discussed. The DAC liquid absorption process has the characteristics of low cost of absorbent raw materials and high selectivity, which can realize a large-scale continuous capture, but high energy consumption in the regeneration process. The DAC solid adsorption process has the characteristics of modularity, low investment cost, and relatively low energy consumption in the regeneration process, but requires a regular replacement of adsorption materials and maintenance of adsorption equipment, which is suitable for small-scale DAC application scenarios. Two typical DAC process absorption/adsorption materials are reviewed. In the DAC electric oscillation adsorption process, CO2 is chemically captured in the solid electrode, and CO2 desorption is achieved by changing the polarity of the solid electrode with applied electric field. This process has a higher efficiency than that of the heat or pressure-based separation process. The CO2 in the air is selected through the DAC separation membrane to achieve an efficient carbon capture. The DAC process achieves the CO2 absorption and desorption through the change of humidity, which breaks through the high energy consumption limit of conventional variable temperature/pressure swing adsorption. The DAC bio-absorption process absor

关键词： Adsorption

Thermal-Hydraulic Characteristics of Helical Cruciform Single Rod Based on Cfd Investigation

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SSRN 2023年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Wang, Xinan Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

The helical cruciform fuel (HCF) takes advantages of strong mixing effects, self-supporting features, and strengthened heat transfer, potential to increase the fuel performance in nuclear reactors. In this work, hydraulic resistance and heat transfer characteristics of an HCF single rod cooled by water were studied based on CFD simulation. Various turbulent models were compared based on experimental data. The velocity field, transverse velocity, wall temperature, and fluid temperature distribution were obtained to discuss influences of geometric sizes on the fuel performance. After 3/8 of the pitch, flow was fully developed. The friction factor and surface heat transfer coefficient were higher with a shorter twist pitch owing to stronger mixing effect while they kept unchanged with variable cross-section sizes but a fixed equivalent diameter. Correlations of friction factor and surface heat transfer coefficient were proposed considering geometric modified coefficients based on a geometric dimensionless number, which were validated with new geometric cases. © 2023, The Authors. All rights reserved.

关键词： Heat transfer coefficients

From Lab to Industry: Scaling-Up Fe-Ni Bimetallic Nano Oxygen Carrier for Mid-Temperature Methane Chemical Looping Reforming

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SSRN 2024年

作者： Tang, Sanli Gai, Zhongrui Li, Yang Liu, Yunlian Liu, Mingkai Pan, Ying Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China University of Chinese Academy of Sciences Beijing100049 China

Chemical looping methane reforming has emerged as a promising avenue to produce blue hydrogen. Currently, the satisfactory CH4 conversion and H2 productivity are usually seen under temperatures above 800 °C. Such temperature requirement poses challenges for industrial reactor design and product gas separation. Investigated widely in chemical looping, bimetallic oxygen carrier has both catalytic and oxygen releasing functions, thus expected to realize both lower reaction temperature and high performance. In this study, we present a nanoscale Fe-Ni bimetallic oxygen carrier for mid-temperature chemical looping methane reforming which can be implemented at large scale. By virtue of a synergy from nanoscale Fe-Ni dispersion, all oxygen carriers from lab-scale to 10-kg scale can operate at 500-600 °C. The lab-scale oxygen carrier was found to convert >90% CH4, produce 3.5 H2 per CH4 molecule with 80-82% overall H2 purity at 575-600 °C. Following the proposed large-scale synthesis workflow, we acquired the 10-kg scale oxygen carrier powder with 70% with 2.8 H2 from per CH4 molecule. The 10-kg powders and beads both persisted phase, morphology and redox stability over 150 cycles. Further explorations revealed the similarity in structure and reaction performance between the lab-scale and 10-kg scale powders, and differences in reaction dynamics between the 10-kg powder and beads. These findings contribute to the mid-temperature chemical looping methane reforming by bridging laboratory practices and industrial application. © 2024, The Authors. All rights reserved.

关键词： Powders

Experimental Study on flow and Heat Transfer of Medium-Prandtl-Number Fluid Along a Hexagonal Helical Cruciform Seven-Rods

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SSRN 2023年

作者： Jiang, Dianqiang Zhang, Dalin Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

A novel type of nuclear fuel named helical cruciform fuel may realize self-supporting for adjacent elements and improve heat transfer, both of which contribute to increasing the power density of the reactor. The flow and heat transfer characteristics of a hexagonal helical cruciform seven-rod bundle were experimentally investigated in the present work. 200 sets of isothermal frictional resistance experiments and 199 sets of heat transfer experiments were finished. The laminar flow region (200 © 2023, The Authors. All rights reserved.

关键词： Reynolds number

Dynamics of two-dimensional water flow in angstrom-scale mono and hybrid channels

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Physical Review Fluids 2024年第12期9卷 124201-124201页

作者： Chengzhen Sun Qiyuan Wang Mehdi Neek-Amal Runfeng Zhou Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Department of Physics Shahid Rajaee Teacher Training University 16875-163 Lavizan Tehran Iran Departement Fysica Universiteit Antwerpen Groenenborgerlaan 171 B-2020 Antwerpen Belgium

We investigate the dynamics of two-dimensional (2D) water flow within angstrom-scale channels (ASCs), a domain scarcely explored in nanofluidics. Our study focuses on the transformation of monolayer water through hybrid channels made of graphene and MoS2, as well as channels where both walls are made of either graphene or MoS2, with sizes ranging from 6 to 8 Å. We find that the transport of monolayer water through ASCs is significantly hindered under low-pressure conditions at nanoscale timescales. To comprehensively explore the flow dynamics, we introduce a refined extension of the Hagen-Poiseuille equation that accounts for frictional slippage dynamics. Our results indicate that hybrid channels exhibit lower flux compared to monochannels. These findings provide valuable insights into the 2D flow mechanisms of monolayer water molecules, highlighting their distinctive interactions with channel walls and unique structural properties.

关键词： flow confinement Nanofluidics Molecular dynamics Navier-Stokes equation

Investigation on the Effect of Hydrothermal Reaction with Cuso4 on Rheological Property of Heavy Oil

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SSRN 2023年

作者： Zhou, Yantao Zhao, Qiuyang Wang, Xuetao Miao, Yan Song, Zhiwei Jin, Hui Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Foshan528216 China

The rheological property is one of important physical properties evaluating heavy oil and asphalt. This work investigated the rheological changes during hydrothermal reaction with CuSO4. The results showed that the addition of CuSO4 at a high reaction temperature had an effect similar to asphalt modifiers, increasing the viscosity and elasticity. Further analysis suggested that the Cu atoms from CuSO4 entered heavy oil molecules, enhancing the interaction attraction between oil molecules. While, at a low reaction temperature, the CuSO4 acted as a catalyst, reducing both viscosity and elasticity. Based on these findings, this work proposed a novel and potential asphalt modification method, which changed the association effect between oil molecules by the chemical reaction to adjust the rheological properties permanently. This method would not fail due to the separation of modifiers and can adjust performance by changing reaction conditions. © 2023, The Authors. All rights reserved.

关键词： Transition metals