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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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Heat and power Load Prediction for Combined Heat and power Station with Different Methods 4

Heat and Power Load Prediction for Combined Heat and Power S...

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4th IEEE International Conference on Digital Twins and Parallel Intelligence, DTPI 2024

作者： Wang, Lin Yu, Tingting Chen, Chen Gao, Yaokui Gao, Lin Qiu, Binbin Liu, Ming Xi'an Thermal Power Research Institute Co. Ltd Xi'an China Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an China

ISBN: (纸本)9798350349252

The accurate short-term load prediction is an essential prerequisite for ensuring the reliable and economic operation of combined heat and power stations. In this study, the heat load and power load prediction models of combined heat and power station were developed with long short-term memory (LSTM) and multiple linear regression (MLR), respectively. The preprocessing and correlation analysis of heat and power loads were conducted. The prediction effects of different prediction models were also compared and analyzed. Taking the data of February as an example, the mean absolute percentage error (MAPE) of heat load prediction with LSTM and MLR models are 3.20% and 3.75%, respectively, and the MAPE of power load prediction are 5.59% and 8.76%, respectively. The prediction results show that the performance of the LSTM model is better than that of the MLR model, and the prediction accuracy of the heat load is higher than that of the power load. © 2024 IEEE.

关键词： Prediction models

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Thermal-Hydraulic Calculation and Analysis on Evaporator System of a 1.00 MW Ultra-Supercritical Pulverized Combustion Boiler with Double Reheat

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Journal of Thermal Science 2021年第3期30卷 807-816页

作者： WAN Li YANG Dong ZHOU Xihong DONG Le LI Juan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

A double reheat ultra-supercritical boiler is an important development direction for high-parameter and large-capacity coal-fired power plants due to its high thermal efficiency and environmental *** has developed a 1.00 MW double reheat ultra-supercritical boiler with steam parameters of 35 MPa at 605℃/61.℃/61.℃.Reasonable water wall design is one of the {1.s to safe and reliable operation of the *** order to examine the thermal-hydraulic characteristics of the double reheat ultra-supercritical boiler,the water wall system was equivalent to a flow network comprising series-parallel circuits,linking circuits and pressure nodes,and a calculation model was built on account of the conservation equations of energy,momentum and *** the iterative solving of nonlinear equations,the prediction parameters of the water wall at boiler maximum continue rate(BMCR),75%turbine heat-acceptance rate(THA)and 30%THA loads,including total pressure drops,flow distribution,outlet steam temperatures,fluid and metal temperatures were *** results of calculation exhibit excellent thermal-hydraulic characteristics and substantiate the feasibility of the water wall design of the double reheat ultra-supercritical boiler.

关键词： double reheat ultra-supercritical boiler water wall flow network method thermal-hydraulic characteristic

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Effect of temperature on Lu’an bituminous char structure evolution in pyrolysis and combustion

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Frontiers in Energy 2021年第1期15卷 14-25页

作者： Yandi ZHANG Yinhe LIU Xiaoli DUAN Yao ZHOU Xiaoqian LIU Shijin XU State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In the process of pyrolysis and combustion of coal particles, coal structure evolution will be affected by the ash behavior, which will further affect the char reactivity, especially in the ash melting temperature zone. Lu’an bituminous char and ash samples were prepared at the N_(2) and air atmospheres respectively across ash melting temperature. A scanning electron microscope (SEM) was used to observe the morphology of char and ash. The specific surface area (SSA) analyzer and thermogravimetric analyzer were respectively adopted to obtain the pore structure characteristics of the coal chars and combustion parameters. Besides, an X-ray diffractometer (XRD) was applied to investigate the graphitization degree of coal chars prepared at different pyrolysis temperatures. The SEM results indicated that the number density and physical dimension of ash spheres exuded from the char particles both gradually increased with the increasing temperature, thus the coalescence of ash spheres could be observed obviously above 1.00℃. Some flocculent materials appeared on the surface of the char particles at 1.00℃, and it could be speculated that β-Si_(3)N_(4) was generated in the pyrolysis process under N_(2). The SSA of the chars decreased with the increasing pyrolysis temperature. Inside the char particles, the micropore area and its proportion in the SSA also declined as the pyrolysis temperature increased. Furthermore, the constantly increasing pyrolysis temperature also caused the reactivity of char decrease, which is consistent with the results obtained by XRD. The higher combustion temperature resulted in the lower porosity and more fragments of the ash.

关键词： bituminous char pyrolysis ash structure evolution reactivity

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Nanoparticle-induced drag reduction for polyacrylamide in turbulent flow with high Reynolds numbers

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Chinese Journal of Chemical engineering 2023年第4期56卷 290-298页

作者： Xiaoping Li Jiaxin Pan Jinwen Shi Yanlin Chai Songwei Hu Qiaorong Han Yanming Zhang Xianwen Li Dengwei Jing State Key Laboratory of Multiphase Flow in Power Engineering&International Research Center for Renewable Energy Xi'an Jiaotong UniversityXi'an 710049China Oil and Gas Technology Research Institute of Petrochina Changqing Oilfield Company Xi'an 710018China

Although having been increasingly studied, there is still controversy as to when the addition of nanoparticles could improve the drag reduction performance of polymer drag reducer and particularly what is the underlying mechanism from the fluid dynamics viewpoint. The drag reduction effects of adding SiO_(2) nanoparticles to various polymer polyacrylamide(PAM) solutions were examined in this *** optimal combination of SiO_(2) nanoparticles with cationic polyacrylamide was ***,the addition of SiO_(2) nanoparticles to cationic polyacrylamide solution was shown to be quite efficient for reducing drag, but only at higher flow rates with Reynolds numbers more than 6000, below which the nanoparticle addition is even negative. The addition of SiO_(2) nanoparticles to the PAM solution is supposed to play a dual role. The first is an increase in flow resistance caused by the Brownian motion of nanoparticles, while the second is a decrease in flow resistance caused by acting as nodes to protect the polymer chain from shear-induced breaking under high shear action. At optimal nanoparticle concentration and under higher Reynolds numbers, the later effect is dominant, which could improve the drag reduction performance of polymer drag reducers. Our work should serve as a guide for the application of natural gas fracturing, where the flow rate is frequently very high.

关键词： Drag reduction SiO_(2)nanoparticle Cationic polymer Brownian motion

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Drag coefficient and volume fraction of bubbles in a supercritical water fluidized bed

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Particuology 2021年第4期19卷 127-138页

作者： Hao Wang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

The supercritical water fluidized bed(SCWFB)is a recently introduced reactor for biomass gasification that does not release *** groups of Geldart B-type quartz sands with different particle sizes were fluidized at a system pressure of 20-27 MPa and system temperature of 41.-570℃.A series of experiments were performed for determining the drag coefficient and volume fraction of *** effects of the particles’size,superficial velocity,system pressure,and temperature on the drag coefficient and volume fraction are *** addition,a correlation between experimental and computed values is demonstrated for both the drag coefficient and volume fraction in *** relative error of the correlation is within±30%.The results of this study provide significant guidance for the scaling-up design of SCWFBs and for the development of supercritical water gasification technology.

关键词： Supercritical water fluidized bed Bubbles Drag coefficient Volume fraction

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Numerical simulation of the drag and heat-transfer characteristics around and through a porous particle based on the lattice Boltzmann method

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Particuology 2021年第5期19卷 99-107页

作者： Mingyue Zhang Qiuyang Zhao Zujie Huang Lei Chen Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Porous particle flow is universal in nature and ***,in previous numerical simulations,porous particles have usually been assumed to be *** is necessary to study the flow and heat-transfer characteristics around porous particles because they are greatly different from those of impermeable *** this study,two-dimensional steady flow and heat transfer around and through a porous particle with a constant temperature placed in a cold fluid were numerically *** effects of the Reynolds number(Re)and Darcy number(Da)on the flow and heat-transfer characteristics were investigated in *** investigated ranges of the parameters were 1.≤Re≤40 and 1.^(−6)≤Da≤1.^(−2).It is sophisticated to simulate porous particles with traditional simulation methods because of their complicated ***,the lattice Boltzmann method was used to solve the generalized macroscopic governing equations because of its *** drag coefficient decreased with increasing Re or Da,but the decrease was not prominent in the range 1.^(−6)≤Da≤1.^(−4).The heat-transfer efficiency of the front surface was much stronger than that of the rear *** heat-transfer efficiency between the particle and the fluid increased with increasing Re or ***,for 1.^(−6)≤Da≤1.^(−4),the increase was not prominent and the heat-transfer enhancement ratio was slightly larger than ***,the effect of Da became more prominent at larger *** addition,new correlations for the drag coefficient and surface-averaged Nusselt number were obtained based on the simulated results.

关键词： Porous particle Darcy-Brinkman-Forchheimer model flow and heat-transfer characteristics Lattice Boltzmann method Correlation

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A Review on Thermal Design of Liquid Droplet Radiator System

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Journal of Thermal Science 2021年第2期30卷 394-417页

作者： CHONG Daotong ZHU Maoguo ZHAO Quanbin CHEN Weixiong YAN Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Liquid Droplet Radiator (LDR) system is regarded as a quite promising waste heat rejection system for aerospace engineering.A comprehensive review on the {1.-of-the-art of LDR system was carried *** thermal design considerations of crucial components such as working fluid,droplet generator and collector,intermediate heat exchanger,circulating pump and return pipe were *** {1.-of-the-art of existing mathematical models of radiation and evaporation characteristics of droplet layer from literatures were ***,thermal designs of three LDR systems were *** weight and required planform area between the rectangular and triangular LDR systems were respectively compared and the evaporation models for calculating the mass loss were *** on the review,some prospective studies of LDR system were put forward in this paper.

关键词： Liquid Droplet Radiator(LDR)system thermal design considerations radiative heat transfer evaporation loss

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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 {1. 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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Void fraction measurement and calculation model of vertical upward co-current air-water slug flow

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Chinese Journal of Chemical engineering 2022年第11期51卷 178-198页

作者： Teng Wang Miao Gui Jinle Zhao Qincheng Bi Tao Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Nuclear Science and Technology Xi’an Jiaotong UniversityXi’an 710049China

The focus of this paper is on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube of 1. mm inner diameter. High-speed photography and optical probes were utilized, with water superficial velocity ranging from 0.089 to 0.65 m·s^(-1.and gas superficial velocity ranging from 0.049 to 0.65 m·s^(-1.. A new void fraction model based on the local parameters was proposed, disposing the slug flow as a combination of Taylor bubbles and liquid slugs. In the Taylor bubble region, correction factors of liquid film thickness Cδand nose shape CZ*were proposed to calculate aTB. In the liquid slug region, the radial void fraction distribution profiles were obtained to calculate aLS, by employing the image processing technique based on supervised machine learning. Results showed that the void fraction proportion in Taylor bubbles occupied crucial contribution to the overall void fraction. Multiple types of void fraction predictive correlations were assessed using the present data. The performance of the Schmidt model was optimal, while some models for slug flow performed not outstanding. Additionally, a predictive correlation was correlated between the central local void fraction and the cross-sectional averaged void fraction, as a straightforward form of the void fraction calculation model. The predictive correlation showed a good agreement with the present experimental data, as well as the data of Olerni et al., indicating that the new model was effective and applicable under the slug flow conditions.

关键词： Slug flow Gas-liquid flow Void fraction Measurement Optical probe Model

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