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SSRN 2022年

作者： He, Xiaotian Cheng, Yiwei Xu, Jinliang Yu, Xiongjiang Xie, Jian Ma, Xiaojing Ren, Yong Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China Key Laboratory of Power Station Energy Transfer Conversion and System of Ministry of Education North China Electric Power University Beijing102206 China Research Group for Fluids and Thermal Engineering University of Nottingham Ningbo China Ningbo315100 China

Boiling of a volatile droplet in a non-volatile liquid becomes complex due to various interface interactions in a solid-liquid-liquid system. Available studies reported explosive boiling and attributed the phenomenon to heterogeneous nucleation due to solid-liquid contact. Here, we investigate boiling of ~2 mm diameter water droplet in a silicon oil pool with glass container. Two transition temperatures are observed, with one as the transition from evaporation to boiling (122.5 o C), and the other as the transition from bubble growth in oil side to that in both oil and water side (160.0 o C). Correspondingly, four boiling modes of evaporation (E), boiling in water (BIW: bubble nucleation at glass-water interface and growth inside drop), boiling in oil (BIO: nucleation at oil-water interface and growth in oil), and boiling in oil and water (BIOW: nucleation at oil-water interface and growth in oil and water), are identified. For the first time, boiling bifurcation is found for drop boiling in a three-phase system. For oil temperature T b in the range of (122.5~160.0) o C, boiling mode switches in between BIW and BIO. On the contrary, for T b beyond of 160.0 o C, either BIW or BIOW occurs. This bifurcation is explained by the fact that a droplet prefers to choose smaller activation energy between that for bubble nucleation at solid-water interface and that for bubble nucleation at oil-water interface. Interfacial instabilities are analyzed to explain why BIOW boils more violently than BIW. Our work presents a comprehensive understanding of droplet boiling in the three-phase system. © 2022, The Authors. All rights reserved.

关键词： Bifurcation (mathematics)

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Strong Photo-Thermal Coupling Effect Boosts Co2 Reduction into Ch4 in a Concentrated Solar Reactor

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SSRN 2023年

作者： Li, Naixu Xu, Lei Ren, Yuqi Liu, Maochang Zhu, Fengfan Cheng, Miao Zhou, Jiancheng Chen, Wenshuai Wang, Ke Wang, Nan School of Chemistry and Chemical Engineering Southeast University No.2 Dongnandaxue Road Jiangsu Nanjing211189 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Shaanxi Xi'An710049 China Key Laboratory of Bio-Based Material Science and Technology Ministry of Education Northeast Forestry University No. 26 Hexing Road Harbin150040 China

This study is dedicated to solving the problems of low energy utilization and low yield in the conventional photocatalytic CO2 reduction process. In this work, a novel concentrated solar (light) reactor was established to improve solar energy utilization efficiency and CO2 conversion rate by concentrating light and heat (that is, by converting light into heat). The TF@TNT/0.4CoOx-0.1CuO monolithic photocatalyst based on titanium foam was designed and prepared. The results showed that the light intensity increased by ~10.6 times (from 400 mW/cm2 to 4266 mW/cm2) while the yield of CH4, the product of CO2 reduction driven by photo-thermal coupling effect, increased by ~220 times (from 0.53 µmol/cm2 to 116.4 µmol/cm2) in the concentrated solar (light) reactor. The results of CH4 yield, electrochemical measurement, and apparent activation energy calculation were investigated in the concentrator reactor under the conditions of concentrated and non-concentrated irradiation of simulated sunlight in different wavelength ranges. It can be found that the concentrated light and the induced photo-thermal coupling effect can significantly reduce the reaction barrier (from 41.62 to 31.51 kJ/mol) and improve the conversion efficiency of solar energy to chemical energy by ~15 times. This provides a potentially feasible method for efficient and green utilization of CO2 driven by solar energy. © 2023, The Authors. All rights reserved.

关键词： Solar energy

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Insight into the Interconversions of Three-Phase Products Through the Supercritical Water Gasification of Bark

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SSRN 2023年

作者： Ge, Hui Yi, Lei Huang, Yong Peng, Pai Cao, Wen Chen, Yunan Qi, Xingang Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'An710049 China International Institute for Innovation Jiangxi University of Science and Technology Jiangxi 341000 China Suzhou Academy Xi’an Jiaotong University No.99 Ren’ai Road Jiangsu Suzhou215123 China

The clean and efficient utilization of biomass waste for hydrogen production conforms to social development in the future. In this work, hydrogen production from supercritical water gasification (SCWG) of fir bark (FB) was investigated systematically at various reaction temperatures (500–750 °C), feedstock concentrations (5%–15%), and retention time (0–40 min). The gaseous, liquid, and solid products were analyzed comprehensively to determine the gasification mechanism. The results demonstrated that FB was the alternative feedstock for hydrogen production. The maximum CE and H2 selectivity of 95.34% and 0.99 were obtained at 700 °C-5%-40 min. High reaction temperature and prolonging retention time accelerated the conversions of phenolic compounds in liquid products and functional groups in solid products. High feedstock concentration also resulted in the bond-making between functional groups in solid products. The reaction mechanism was proposed based on the components of gaseous and liquid products and the variations of functional groups in solid products. © 2023, The Authors. All rights reserved.

关键词： Hydrogen production

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A 3d Ptco Degradation Model for Long-Term Performance Prediction of a Scaled-Up Pemfc Under Constant Voltage Operation

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SSRN 2023年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Zhao, Jian Wei, Lei Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Center for Advanced Vehicular Systems Mississippi State University Starkville39762 United States Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

The non-uniform distribution of reactants, pressure, temperature, and reaction rate, in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3% after 80,000 hours operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its nonuniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime. © 2023, The Authors. All rights reserved.

关键词： Proton exchange membrane fuel cells (PEMFC)

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Energy consumption characteristics and energy saving potential of thermal power plants under ultra-low power load ratio conditions

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Energy 2025年 330卷

作者： Zeyu Du Ming Liu Yang Wang Yu Zhou Yongliang Zhao Junjie Yan Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi’an 710049 China China Huaneng Group Co LTD Beijing 100032 China

The operational flexibility of thermal power plants should be enhanced to accommodate the high penetration of photovoltaic and wind power within the power grid. The energy efficiency deteriorates heavily when thermal power plants operate under ultra-low power load ratio conditions, which will increase the carbon emissions of the low-carbon power system. To achieve the energy saving under ultra-low power load ratio condition, the CFPP's (coal-fired power plant) off-design condition models were developed, and the thermal system regulation with additional losses of the CFPP operates under below 30 % power load ratio condition was simulated. Then, influences of the degradation factors on the energy consumption characteristics under ultra-low power load ratio condition were evaluated. Moreover, the carbon emission rate of power generation considering the renewable power accommodation was evaluated. Results show the degradations of turbines' internal efficiencies are the main source of internal losses, and the degradation of boiler's efficiency and the increase of the auxiliary power ratio are the main source of external losses. The total carbon emission rate of power generation decreases by 21.98 g/(kW h) with the power load ratio of CFPP decreasing from 30 % to 20 % due to the increased accommodation of renewable power. Finally, energy saving potential evaluations under ultra-low power load ratio conditions were conducted. The net coal consumption rate is 298.56 g/(kW h) and 522.39 g/(kW h) when the thermal power plant operates under 100 % and 20 % power load ratio conditions respectively. The maximal energy saving potential of b net under ultra-low power load condition are 87.25, 29.47, 25.05, 2.33 and 1.05 g/(kW h), for the degradation of isentropic efficiency of turbine, the degradation of boiler's efficiency, the increase of auxiliary power ratio, the additional drainage water of the boiler and the switching action of BFPT's supply steam, respectively.

关键词： Fossil fuel power plants

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Numerical study of collision behavior of melt drops during fuelcoolant interaction

Numerical study of collision behavior of melt drops during f...

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2020 International Conference on Nuclear engineering, ICONE 2020, collocated with the ASME 2020 power Conference

作者： Wen, Panpan Li, Gen Gao, Jinchen Li, Yupeng Yamaji, Akifumi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Cooperative Major in Nuclear Energy Waseda University Tokyo169-8555 Japan

ISBN: (纸本)9780791883785

The collision dynamics between two droplets plays an important role in various disciplines of nature and practical interests, such as fuel-coolant interaction (FCI), fuel combustion in engines, and various spraying process. FCI presents in nuclear reactor severe accident when the melt relocates into the coolant in the lower head with violent disturbance and vigorous heat transfer. The purpose of this study is to investigate the collision behavior of melt droplets during fuel-coolant interaction. The collision of two equal-sized droplets has been simulated in 3D by using the volume of fluid (VOF) and adaptive mesh refinement method. The numerical simulations of tetradecane droplet collision were carried out to validate the numerical methods. The results showed good agreement with the experiments. Furthermore, the simulations of uranium dioxide (UO2) droplets collision in coolant were carried out. The results showed that the contact area between droplets and coolant increased with time first and then decreased. With the increase of Weber number, the contact area of maximum in the droplet collision increased. Break happened in the later period and many child droplets formed. The number of child droplets increased with the increase of Weber number. In addition, the size distribution of little droplets was investigated. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Coolants

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Comparison of Chemical Composition and Acidity of Size-Resolved Inorganic Aerosols at the Top and Foot of Mt. Hua, Northwest China: The Role of the Gas-Particle Distribution of Ammonia

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SSRN 2023年

作者： Li, Jianjun Feng, Qiao Liu, Haijiao Dai, Wenting Cao, Yue Shen, Minxia Liu, Yali Qi, Weining Chen, Yukun Guo, Xiao Zhang, Yifan Li, Lu Zhou, Bianhong State Key Laboratory of Loess and Quaternary Geology Key Lab of Aerosol Chemistry and Physics Institute of Earth Environment Chinese Academy of Sciences Xi’an710061 China College of Geography and Environment Baoji University of Arts and Sciences Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation Baoji721013 China Xi’an Institute for Innovative Earth Environment Research Xi’an710061 China National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain Shaanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Aerosol pH is not only a diagnostic indicator of secondary aerosol formation, but also a key factor in the specific chemical reaction routes that produce sulfates and nitrates. To understand the characteristics of aerosol acidity in the Mt. Hua, the chemical fractions of water-soluble inorganic ions in the atmospheric PM2.5 and size-resolved particle at the top and foot of Mt. Hua in summer 2020 were studied. The results showed the mass concentrations of PM2.5 and water-soluble ions at the foot were 2.0-2.6 times higher than those at the top. The secondary inorganic ions, i.e. SO42-, NO3-, and NH4+ (SNA) were 56%-61% higher by day than by night. SO42- was mainly distributed in the fine particles (Dp 2.1 µm) was mainly attributed to the gaseous HNO3 volatilized from fine particles reacting with cations in coarse particles to form non-volatile salts (such as Ca(NO3)2). The pH values of PM2.5 were 2.7 ± 1.3 and 3.3 ± 0.42 at the top and foot, respectively. NH4+/NH3(g) plays a decisive role in stabilising aerosol acidity. In addition, the increase of the liquid water content (LWC) at the foot facilitates the gas-particle conversion of NH3, while the H+ concentration was diluted, resulting in a decrease in acidity at the foot. NH4+/NH3 had good linear correlations with SO42−, NO3－, and LWC during the daytime at both sites, indicating that SO42−, NO3－, and LWC together affect the gas-particle distribution of ammonia by day: however, the effect of LWC at night was not evident. © 2023, The Authors. All rights reserved.

关键词： Ammonia

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A novel coal-fired chp system integrated with steam ejectors to realize heat-power decoupling and energy saving

A novel coal-fired chp system integrated with steam ejectors...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Liu, Miaomiao Liu, Ming Zhao, Shuran Song, Gege Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Key Laboratory of Heat Transfer enhancement and Process Energy Conservation Technology Ministry of education Beijing University Beijing100025 China

ISBN: (纸本)9780791883747

Traditional combined heat and power (CHP) units should run in the heat-controlled mode. The adjustable range of power load is restricted by the heat load, and the minimum power load increases with the heat load. Because of high penetration of intermittent renewable power, operational flexibility of CHP units is highly required. It is necessary to adopt some technical solutions to realize heat-power decoupling for CHP units. To find a heat-power decoupling method with low investment and high energy efficiency, the steam ejectors, simple in structure and low in cost, are applied to design a novel heat-power decoupling system in this study. Steam ejectors can recover the waste heat of exhaust steam of steam turbines. Therefore, the integration of steam ejector may realize heat-power decoupling and energy saving simultaneously. Three heat-power decoupling systems with steam ejectors are designed. The heat-power decoupling performance and energy consumption characteristics of these systems are investigated with a reference 330 MW coal-fired CHP unit. Results show that all three modified systems can realize heat-power decoupling. The heat-power decoupling performance of improved system III is the best, and improved system I has the least coal consumption rate for power generation. Copyright © 2020 ASME.

关键词： Thermal load

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Corrigendum to ‘Experimental investigation of the microlayer and dry spot dynamic characteristics in a small channel flow boiling by laser interferometry method’ [International Journal of Heat and Mass Transfer 201 (2023) 123585]

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International Journal of Heat and Mass Transfer 2023年 209卷

作者： Zhong-Xiang Shen Ming Gao Wu-han Dong Li-xin Zhang Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China

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Fluoride-Salt-Cooled High-Temperature Reactor: An Integrated Nuclear-Based Energy Production and Conversion System

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SSRN 2023年

作者： Zhang, Dalin Li, Xinyu Jiang, Dianqiang Zhou, Xingguang Lv, Xindi Yun, Shichang Wu, Wenqiang He, Xuanang Li, Haoyang Min, Xin Chen, Kailong Tian, Wenxi Qiu, Suizheng Su, Guanghui Zhao, Quanbin Fu, Yao Tang, Chuntao Zhuo, Wenbin Li, Jinggang Zuo, Jiaxu 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 Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai201800 China Shanghai Nuclear Engineering Research & Design Institute Co. Ltd. Shanghai200233 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China China Nuclear Power Technology Research Institute Guangdong Shenzhen518000 China Nuclear and Radiation Safety Center Ministry of Ecology and Environment Beijing100082 China

Based on the analysis of energy structure and the development trends of advanced nuclear energy technology, combining the complementary advantages of nuclear energy and other energy sources in China, the Fluoride-salt-cooled High-temperature Reactor(FuSTAR) system has been proposed. FuSTAR system is designed to address production capacity issues in areas with energy shortages or resource concentration and can be combined with high-temperature process heat to achieve high-value-added processes such as hydrogen production. In this paper, the design and optimization processes of FuSTAR are described from three aspects: the neutronic and thermal-hydraulic system, the thermal transport system, and the power cycle system. Tri-structural isotropic fuel combined with helical cruciform elements has been studied in detail on the neutron physics and thermal-hydraulic properties, and the flow and heat transfer experiment is carried out for the first time. The multilayer nonlinear programming method has been applied to the design of thermal transport systems and the passive residual heat removal system and proved to be fast and efficient. Then the optimal parameters and configuration of the thermoelectric conversion system are obtained directly by using the superstructure optimization method, which saves computing resources greatly. Based on the above design and parameters, the inherent safety of FuSTAR is demonstrated through deterministic safety analysis. In addition, the iodine-sulfur cycle technology is also designed and analyzed, and the characteristics of tritium production in FuSTAR are calculated. The research provides important guidance for the detailed design and operation of FuSTAR. Moreover, this study highlights the significant potential of integrating nuclear energy with other energy sources in an optimized energy-production system. Based on the current research findings, prospects for future research directions are also suggested. © 2023, The Authors. All rights r

关键词： High temperature reactors

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