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Bubble oscillation and effects of dynamic behaviors on forces and mass transfer in photoelectrochemical water splitting

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Physical Review Fluids 2024年第11期9卷 114305-114305页

作者： Yonglu She Qiang Xu Tengfei Nie Xinyi Luo Mengsha Wang Xingmiao Ye Dengwei Jing State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The evolution and coverage of bubbles resulting from gas evolution at the reaction interface significantly impact mass transfer and the flow field within the photoelectrochemical water splitting system, posing a significant obstacle to overcoming the efficiency bottleneck of photoelectrochemical water splitting. In situ bubble observation can be realized via a coupled experimental system combining electrochemical measurements and high-speed imaging. The results indicate that bubble growth behavior correlates with system temperature and operating voltage; that is, the bubbles grow in an oscillating state on the electrode surface at the low operating voltage and high system temperature. Besides, the deviation amplitude of oscillating bubbles increases with system temperature yet decreases with operating voltage. The results indicate that the time coefficient of the growing bubble decreases, while the growth rate and gas evolution efficiency of the bubble increase with the increase of oscillating amplitude in the horizontal direction. The study of dynamic behaviors between the oscillating bubble and the contacted electrode reveals that the bubble oscillation is characterized by the periodic contraction and extension of the triple line. The mass transfer model of concentration boundary layer and the force model of oscillating bubble are constructed based on the interaction between the bubbles and the surrounding flow field. The mass transfer model has considered the microconvection caused by single-phase natural convection, gas-liquid interface expansion, and the oscillation of bubbles. Then through the force balance model, the solutal Marangoni force is found to gradually increase as the contact line extends outward.

关键词： Bubble dynamics Contact line dynamics Marangoni convection Microbubbles multiphase flows

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Study on startup characteristic of a supercritical carbon dioxide Brayton cycle coupled with heat pipe cooled reactor 20

Study on startup characteristic of a supercritical carbon di...

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20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023

作者： Wang, Zheng Zhang, Minghui Xu, Shihao Gou, Junli Shan, Jianqiang State Key Laboratory of Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi'an Jiaotong University Shaanxi Xi'an China

ISBN: (纸本)9780894487934

Nuclear energy is a viable choice for Unmanned Undersea Vehicles (UUVs) due to its high density and long operation life. However, traditional PWRs aren't suited to underwater working environments. To provide a safe and reliable power source for UUV, a new nuclear power plant coupled with the supercritical CO2 Brayton cycle and heat pipe cooled reactor is proposed. This provides the advantages of high reliability, high safety and high expansion ability. In this work, a simulation code for the new nuclear power plant is developed, which includes a reactor kinetics model, a core heat conduction model, a two-dimensional heat pipe network model, and a closeCO2 Brayton cycle model. In order to verify the accuracy of the model, the date of the experiment is compared with the model. And the design value of the new nuclear power plant has been modeled by this code. Meanwhile, the control strategies for start-up of the new nuclear power plant are proposed, including core startup, heat pipe startup and supercritical carbon dioxide Brayton loop startup. By utilizing the control strategies, the code has researched the operational characteristics of the start-up of heat pipe-cooled reactors. The development of this code provides a reference for the new nuclear power plant. © 2023 Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023. All rights reserved.

关键词： Brayton cycle

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Performance Analysis of Low GWP Refrigerants R1234yf and R448A in a Small High and Low-temperature Test Equipment

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Recent Patents on Mechanical engineering 2022年第3期15卷 277-284页

作者： Liqiang, Zhou Zhang, Hua Zilong, Wang Wenjing, Gao School of Energy and Power University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

Aim: The article presents an analysis of the feasibility of R1234yf and R448A, two new low GWP refrigerants, as alternatives to R404A in the refrigeration system of small high and low-temperature test equipment. Methods: The physical properties of R448A and R404A are similar. Compared with R404A, the GWP of R1234yf and R448A reduced by 99.9% and 67.7%, respectively. The analysis is based on an experimental comparison of R404A with R448A and R1234yf, comparing the compressor discharge tempera-ture, COP, cooling capacity, and the cooling rate of three refrigeration systems at different ambient temperatures. Results: The experimental results show that the cooling capacity of R448A is better than R404A at a higher condensing temperature. Conclusion: When the charging volume is 230g, and the ambient temperature is 25°C, the COP of the R448A system is increased by about 24.63% compared with the R404A system. © 2022 Bentham Science Publishers.

关键词： Refrigerants

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Experimental investigation on separation characteristics of axial cyclone separator

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Science China(Technological Sciences) 2023年第11期66卷 3231-3244页

作者： WANG JinZhi WANG YeChun HAN JinZai XU Qiang XIE XiangDong PAN YingXiu GUO LieJin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Xinjin Weihua Institute of Clean Energy Research Foshan 528216China Aero Engine Corporation of China(AECC)Shenyang Engine Research Institute Shenyang 110015China

Axial cyclone separator has been widely applied in chemical production as an efficient gas-liquid separation *** this study,a new axial cyclone separator with integrated swirler and exhaust pipe is designed to achieve the development goal of compact structure for advanced engine,and the distribution characteristics of swirling flow patterns as well as the variation in separation characteristics are investigated under slug flow *** on flow visualizations and fluctuation characteristics of pressure signals,three typical flow patterns,namely,slug flow,swirling intermittent flow,and swirling annular flow,in the horizontal swirling separation flow are *** is investigated how the inlet conditions affect the separation characteristic *** separation purity and extreme points of the air separation efficiency are independent of the inlet liquid flow *** separation pressure drop is quadratically related to the inlet air flow *** on the drift-flux model and other methods,the prediction methods for the air separation efficiency and pressure drop are proposed,and the prediction accuracy is within±20%,which may provide instructions for the practical application of axial cyclone separator.

关键词： axial cyclone separation gas-liquid two-phase flow flow pattern in the swirling flow separation characteristics

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A universal charge-compensating strategy for high-energy-density pseudocapacitors

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Journal of Energy Chemistry 2023年第3期78卷 333-339,I0010页

作者： Baoyi Yin Jiaqi Zhang Yuanhui Su Yu Huan Liang Hao Chen Wang Xun Hu Tao Wei School of Material Science and Engineering University of Jinan336 Nanxinzhuang West RoadJinan 250022ShandongChina School of Microelectronics Dalian University of TechnologyDalian 116024LiaoningChina Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai 200093China State Key Laboratory of ASIC and Systems School of MicroelectronicsFudan UniversityShanghai 200433China

For pseudocapacitive electrode materials(PseEMs),despite much progress having been made in achieving both high power density and high energy density,a general strategy to guide the enhancement of intrinsic capacitive properties of PseEMs remains ***,we demonstrate a universal chargecompensating strategy to improve the charge-storage capability of PseEMs intrinsically:ⅰ) in the electrolyte with anion as charge carriers(such as OH-),reducing the multivalent cations of PseEMs into lower valences could create more reversible low-to-high valence redox cou ples to promote the intercalation of the anions;ⅱ) in the electrolytes with cation as charge carriers(such as H^(+),Li^(+),Na^(+)),oxidizing the multivalent cations of PseEMs into higher valences could introduce more reversible high-to-low valence redox couples to promote the intercalation of the *** we demonstrated that the improved intrinsic charge-storage capability for PseEMs originates from the increased Faradaic charge storage sites.

关键词： Supercapacitors Universal charge-compensating strategy Changed valence state Increased Faradaic charge storage sites

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Experimental investigation of nano-particle deposited wick Structure's heat transfer characteristics

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International Journal of Advanced Nuclear Reactor Design and Technology 2022年第4期4卷 196-204页

作者： Han, Ruiyu Wang, Zetao Guo, Kailun Wang, Chenglong Zhang, Dalin Tian, Wenxi Qiu, Suizheng 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

Recently, nanotechnology attracts more and more attention in heat transfer system. Many studies have shown that using nanofluid as the working fluid can improve the thermal performance of the heat pipe. In this paper, the preliminary effort of applying nano-surface engineering on the heat pipe wick to fabricate the nano-structured wick structure has been carried out. Experimental investigation has been performed to determine the effect of the heat source power, mesh aperture and the wick surface structure on the total thermal resistance of the wick structure. When the heat source power increased from 20 W to 30 W, then to 50 W, the evaporation resistance decreases 25.9% and 13.7% respectively, while the conduction resistance increases 24.8% at first and then decreases 9.5%. The evaporation resistance is less with than without the wick structure, and it increases with the increase of mesh aperture. When the mesh aperture increases from 75 μm to 150 μm, then to 460 μm, the evaporation resistance increases 1.9% and 1.7% respectively. Whereas, the wick structure, as well as the mesh aperture have slight influence on the conduction resistance. The experimental results suggest that the nano structure on the surface can efficiently decrease the evaporation resistance but increase the conduction resistance at the same time. Compared to the wick structure with smooth surface, the evaporation resistance of nano-surface deposited by 0.01% TiO2 and 0.02% TiO2 has decreased 4.3% and 15.5%, respectively. This study provides a reference for the preparation of the heat pipe with greater performance in the future. © 2022 Xi'an Jiaotong University

关键词： Wick structure Nano structure Thermal resistance

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Porous fixed-bed photoreactor for boosting C-C coupling in photocatalytic CO_(2)reduction

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eScience 2022年第4期2卷 428-437页

作者： Shengjie Bai Haoran Qiu Mengmeng Song Guiwei He Feng Wang Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'anShaanxi710049China

Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass ***,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)*** photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic *** find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension *** larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.

关键词： Photocatalytic CO_(2)reduction Cu/Cd_(0.5)Zn_(0.5)S Porous fixed-bed Three-phase interface C^(2+)chemical fuel

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Life Cycle Assessment Analysis and Comparison of 1000 MW S-CO_(2)Coal Fired power Plant and 1000 MW USC Water-Steam Coal-Fired power Plant

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Journal of Thermal Science 2022年第2期31卷 463-484页

作者： LI Mingjia WANG Ge XU Jinliang NI Jingwei SUN Enhui Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing 102206China

The objective of this paper is to understand the benefits that one can achieve for large-scale supercritical CO_(2)(S-CO_(2))coal-fired power *** aspects of energy environment and economy of 1000 MW S-CO_(2)coal-fired power generation system and 1000 MW ultra-supercritical(USC)water-steam Rankine cycle coal-fired power generation system are analyzed and compared at the similar main vapor parameters,by adopting the neural network genetic algorithm and life cycle assessment(LCA)***-objective optimization of the 1000 MW S-CO_(2)coal-fired power generation system is further carried *** power generation efficiency,environmental impact load,and investment recovery period are adopted as the objective *** main vapor parameters of temperature and pressure are set as the decision *** results are concluded as ***,the total energy consumption of the S-CO_(2)coal-fired power generation system is 10.48 MJ/k Wh and the energy payback ratio is 34.37%.The performance is superior to the USC coal-fired power generation ***,the resource depletion index of the S-CO_(2)coal-fired power generation system is 4.38μPRchina,90,which is lower than that of the USC coal-fired power generation system,and the resource consumption is ***,the environmental impact load of the S-CO_(2)coal-fired power generation system is 0.742 m PEchina,90,which is less than that of the USC coal-fired power generation system,0.783 m PEchina,*** all environmental impact types,human toxicity potential HTP and global warming potential GWP account for the most environmental ***,the investment cost of the S-CO_(2)coal-fired power generation system is generally less than that of the USC coal-fired power generation system because the cost of the S-CO_(2)turbine is only half of the cost of the steam *** optimal turbine inlet temperature T_(5)becomes smaller,and the optimal turbine inlet pressure is unchanged at 622.082°C/30 MPa.

关键词： S-CO_(2)power plant ultra-supercritical water-steam Rankine cycle power plant life cycle assessment energy efficiency environment impact economic performance

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Preliminary study on FROBA-SCO2 with transient models and its application for Reactivity Initiated Accident and loss of flow accident

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International Journal of Advanced Nuclear Reactor Design and Technology 2022年第3期4卷 101-108页

作者： Yang, T.A. Zhang, K. Yang, H.K. Tian, W.X. Qiu, S.Z. 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

As a coolant enabling the reactor with a high efficiency and low volume, the supercritical CO2 has becoming a hot topic nowadays. However, the fuel rod behaviors under accidents are not studied thoroughly, especially the interaction between the coolant and the cladding. With the previous study of fuel rod behaviors analysis of supercritical CO2 cooled nuclear reactor under steady state operation, transient state models are implemented and the upgraded code can be used to predict the fuel rod behaviors under RIA and LOFA. After the comparation of the calculation results with SACOS-SCO2, the tendency and numerical value are close, so the accuracy is warranted. The upgraded FROBA-SCO2 is used to predict the fuel rod behaviors under RIA and LOFA conditions and the results indicate that the maximum temperature of cladding and fuel is within safety limits. © 2022

关键词： Coolants

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Unconventional energetics of small vacancy clusters in BCC high-entropy alloy Nb_(0.75)ZrTiV_(0.5)

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Journal of Materials Science & Technology 2023年第15期146卷 61-71页

作者： Tan Shi Xi Qiu Yundi Zhou Sixin Lyu Jing Li Dan Sun Qing Peng Yong Xin Chenyang Lu School of Nuclear Science and Technology Xi’an Jiaotong UniversityXi’an 710049China Nuclear Power Institute of China Chengdu 610213China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

The stability of small vacancy clusters including divacancy,trivacancy and tetravacancy has been studied in body-centered cubic high-entropy alloy Nb_(0.75)ZrTiV_(0.5) in structures of random solid solution and short-range order by first-principles calculations and molecular dynamics *** from conventional body-centered cubic metals,the tightly bound configurations have a lower structural stability and are not preferred energetically in the studied high-entropy *** of vacancy configurations leads to vacancy-atom exchanges that favor less compact *** formation energy of small vacancy clusters is much smaller than its constituent elements of Nb and V due to the large structural adjustment induced by severe local lattice *** difference in local lattice distortion and elemental arrangement in the vacancy neighborhood leads to significant site-to-site variation in vacancy cluster energy and *** formation energy has a strong correlation with the local energy state of the vacancy configuration and the extent of structural *** to random solid solution,the structure of short-range order has a higher stability for the most compact cluster configurations and tends to have higher vacancy cluster formation *** to classical molecular dynamics simulations of cluster diffusion at high temperature,the studied high-entropy alloy has a higher probability of cluster dissociation compared to Nb and *** unconventional energetics of small vacancy clusters is expected to have a profound impact on their generation,diffusion,dissociation,coalescence,as well as the defect microstructure evolution during irradiation.

关键词： Refractory high-entropy alloys Small vacancy clusters First-principles calculations Defect energetics Radiation defect evolution

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