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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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N and O vacancies regulation over semiconductor heterojunction to synergistically boost photocatalytic hydrogen peroxide production

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Journal of Materials Science & Technology 2024年第29期196卷 237-247页

作者： Chaoqian Ai Bing Luo Chunyang Zhang Yadi Wang Baoyuan Wang Lijing Ma Dengwei Jing International Research Center for Renewable Energy&State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Department of Chemical Engineering School of Water and Environment&Key Laboratory of Subsurface Hydrology and Ecology in Arid AreasMinistry of Education Chang’an UniversityXi’an 710054China

Defect engineering represents a potent strategy for the modification of electronic properties by introducing atomic vacancies in ***,the synergistic enhancement attributable to different types of atomic vacancies within a heterojunction,as well as their underlying mechanisms,remains sparsely ***,the flexible g-C_(3)N_(4)materials with varying nitrogen vacancies were prepared via a facile calcination method under different atmospheric conditions and then composited with CeO_(2)nanocubes to construct Z-scheme *** was observed that CeO_(2)has abundant O vacancies,and the g-C_(3)N_(4)form tertiary nitrogen defects at the center of the heptazine units under an NH3 atmosphere *** resulting enhancement in the interfacial built-in electric field,coupled with the synergistic effect of O and N vacancies within the Z-scheme heterojunction,has been demonstrated to significantly enhance charge transfer *** results in an optimized photoactivity with a H_(2)O_(2)generation rate of 2.01 mmol g^(-1)h^(-1).This work opens an avenue for constructing and optimizing the heterogeneous photocatalysts by defect engineering technology,and provides deep insight to understand the nature of vacancy engineering in designing effective catalysts for solar energy conversion.

关键词： Photocatalysis H_(2)O_(2) production Z-scheme Defect engineering Synergy effect

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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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STUDY ON OPTIMAL HEAT-power DISPATCH CONSIDERING DISTRICT HEATING SYSTEM THERMAL INERTIA 37

STUDY ON OPTIMAL HEAT-POWER DISPATCH CONSIDERING DISTRICT HE...

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37th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2024

作者： Wang, Liyuan Fu, Yue Liu, Ming Liu, Jiping MOE Key Laboratory of Thermal Fluid Science Engineering Xi'an Jiaotong University Shanxi Xi'an China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shanxi Xi'an China

ISBN: (纸本)9798331307660

As the global climate change and increasing requirement for thermal comfort of human, the thermal demand in the heating period is gradually climbing. The district heating system (DHS) with combined heat and power (CHP) units as the heat source is the major heating method in northern China, and exploring the flexibility enhancement way of CHP units is a key issue. The main ways to improve the flexibility of CHP units are heating unit modification and utilization of external energy storage. At the same time, there is a large amount of thermal storage in the DHS, which can be used to achieve the same effect as using hot water tank thermal storage, and can reduce the heating unit's own renovation and lower costs. In the integrated heat and power scheduling optimization, the cost is generally used as the optimization objective, but the amount of coal consumption under different operating conditions of CHP is less considered in the cost of CHP units as heat sources. In this paper, the dynamic model of the system considering the heat storage of the DHS heat network is established, and the coal consumption of CHP unit is added to the system operating cost. The study shows that the costs is negatively correlated with the water temperature of the heat network and positively correlated with the mass flow rate of heating steam, while higher CHP operating conditions increase the total operating cost. © 2024 37th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2024. All rights reserved.

关键词： Coal storage

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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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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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Experimental Investigation on Hydrophobic Behavior of Carbon Spheres Coated Surface Made from Microplastics

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Journal of Renewable Materials 2021年第12期9卷 2159-2174页

作者： Peng Liu Bin Bai Cui Wang Yunan Chen Zhiwei Ge Wenwen Wei Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

In this paper,a simple method to plate a hydrophobic coating on the inner surface of a small-scaled tube was proposed,where the coating consisted of carbon *** common plastics polystyrene,polycarbonate and polyethylene were used as the feedstocks to be processed in supercritical water in a quartz tubular *** reaction,the contact angle of droplet on the inner surface of the quartz tube was turned out to be over 100°,significantly larger than that of the blank tube 54°.When processing polystyrene in the 750℃ supercritical water for 10 min,the largest contact angle was obtained,up to 145°.Besides,in this sample,the size of carbon spheres was smallest,about 2.09μm diameter on *** comparing among different types of plastics under the same condition,the contact angle of surface made from PC took the dominant position over that of PS and PE,124°,100°and 90°,*** the sample made from PC,carbon spheres adhered into a mountainlike shape,producing a binary geometric ***,this research could be helpful in the discussion of plastic waste management and carbon spheres fabrication with low cost.

关键词： Plastic wastes hydrothermal method carbon spheres supercritical water hydrophobicity

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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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Heat Transfer Enhancement of Supercritical Carbon Dioxide and Liquid Lead Bismuth Eutectic Compact Heat Exchanger 20

Heat Transfer Enhancement of Supercritical Carbon Dioxide an...

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

作者： Liu, Shuhan Liu, Ji'an Liu, Qingjiang Lei, Xianliang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 West Xianning Road Xi'an710049 China

ISBN: (纸本)9780894487934

Lead cooled fast reactor (LFR) is the fourth generation reactor system with great development potential;Supercritical carbon dioxide (S-CO2) Brayton cycle is also considered as the most promising energy system due to its high efficiency and compactness, good flexibility. Their combination is undoubtly considered as one of the most ideal power cycles. In this union system, the intermediate heat exchanger plays a key role in the entire power system. Considering the thermo-physical properties and heat transfer behaviors in both S-CO2 and liquid lead bismuth eutectic (LBE) are significantly different, an asymmetric compact coupled heat exchanger learning from Honeycomb structure is proposed. Then the effect of Reynolds number on the coupling heat transfer is discussed. It is found that the thermal resistance mainly exists in the cold side. In order to enhance the heat transfer in the S-CO2 side, wave channels are used on the cold side. The results show that the wave channels can significantly improve the field synergy of the fluid near the wall;With the increase of wave amplitude, the heat transfer coefficient and the friction factor of the cold side channel increases;The comprehensive heat transfer coefficient PEC is used to evaluate the heat transfer behavior. When the PEC number is the largest, the overall heat transfer coefficient of the heat exchanger is 1.56~1.81 of the straight channel in the range of Re=86700~145000. © 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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The effects of thermal properties on interphase heat transfer between supercritical water-particle flow

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Physics of Fluids 2025年第6期37卷

作者： Li, Xiaoyu Zhang, Bowei Li, Yi Jin, Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The interphase heat transfer of particle flow is of significant importance. This work employed the particle-resolved direct numerical simulation to calculate the interphase heat transfer of supercritical water (SCW)-particle flow. In particular, the influences of complex variations in nonlinear physical properties of SCW has been considered. The results reveal the opposing effects of nozzle effect and particle interaction on the heat transfer. The large Prandtl number (Pr) in critical zone predominantly enhances heat transfer. However, the increase in density weakens the influence of nozzle effect, diminishing the enhancing effect of larger Pr. The strength of interphase heat transfer varies under different conditions, and the influences of variations in density and Pr distribution are also different. As a result, the correlations for the normalized heat transfer coefficient N with varying constants are established. Furthermore, based on the differing dominances of nozzle effect and particle interaction, an appropriate Nusselt number (Nu) correlation for heat transfer of particle flow is developed for most cases. The correlation for SCW-particle flow interphase heat transfer Nu can be obtained by coupling the Nu and N correlations. It shows good predictive performance. © 2025 Author(s).

关键词： Prandtl number

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