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Experimental and theoretical study of vapor/air mixture condensation inside an inclined blind-end pipe in natural convection with considering fog formation

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2022年 184卷

作者： Tan, Bing Cai, Jiejin Zhao, Jiyun Hibiki, Takashi Tian, W. X. Wu, Y. W. Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China South China Univ Technol Sch Elect Power Guangzhou 510640 Peoples R China City Univ Hong Kong Dept Mech Engn Kowloon Tat Chee Ave Hong Kong Peoples R China

This study investigated the vapor condensation characteristics in an inclined pipe under natural convection conditions experimentally and numerically. The inclined blind-end concentric pipe had an inner diameter of 134 mm and a length of 680 mm, which is cooled by cooling water. The experimental pressure range was 0.2-0.6 MPa, and the dimensionless mass number range was 0.44 to 202. The fog formation phenomenon was observed in the experiment. An empirical correlation with a broad range of dimensionless mass numbers was developed based on the experimental results to predict the heat transfer coefficient (HTC). When the air mass fraction was large and the HTC was low, the effect of fog formation on the HTC had to be considered. In the numerical simulation, this study aimed to develop an HTC prediction model with broader applicability. Based on the diffusion boundary layer theory, this study improved Peterson's model by adding fog effect and wave effect. The model showed high adaptability to this experiment and other experiments in the natural convection condensation database. The improved model performed significantly better, with 96% of the data falling within an error zone of 30%. The wide range of dimensionless mass number test data might complement the natural convection condensation experimental database. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Modeling Fog formation Suction effect Condensation Heat and mass transfer

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Development of mechanistic cladding rupture model for integrated severe accident code ISAA. Part I: Module verification and application in CAP1400

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ANNALS OF NUCLEAR ENERGY 2021年 158卷

作者： Gao, Pengcheng Zhang, Bin Li, Jishen Tang, Shaowei Shan, Jianqiang Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Cladding rupture is an important demarcation point for severe accidents. Most severe accident analysis codes are based on simple parameter models to determine the damage of the cladding. This paper uses the thermal-mechanical model to develop a core Fuel Rod Thermal-Mechanical Behavior analysis (FRTMB) module to analyze the fuel mechanical behavior. The purpose is to judge the cladding rupture with the severe accident analysis code. The model consists of thermal, mechanical and material property parts. The correctness of the model is verified by comparing with the experimental results of related fuel rods. Finally, the FRTMB module is integrated into the severe accident analysis code to evaluate the thermal-mechanical behavior of fuel rods in different enrichment areas of CAP1400 reactor, so as to provide a basis for judging cladding rupture in severe accidents. The mechanical analysis results show that the gap will close earlier under high-power condition. The results explain the necessity for considering the fuel performance in core analysis and demonstrate applicability of the FRTMB module integrated into the severe accident analysis code. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Code development Severe accident Fuel behavior Cladding rupture CAP1400

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Surface coke deposition influences on flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2021年 122卷

作者： Cheng, Xiang Feng, Song Bi, Qincheng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn 28 West Xianning Rd Xian 710049 Peoples R China China Aerodynam Res & Dev Ctr Mianyang 621000 Sichuan Peoples R China

Surface coke deposition influences on the flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts were experimentally investigated at supercritical pressures, to research the active cooling technology of new flying vehicles. The SS304 test tubes had a 4 mm inner diameter and a 6 mm outer diameter. The twist ratios of the two types of twisted-tapes are 6.31 and 12.63. The experimental system pressure, outlet temperature, and mass flow rate were fixed at 3 MPa, 893.15 K, and 1.20 g.s(-1), respectively. The results indicated that the twisted-tape insert mixed the fluid, washed coke deposited on the inner wall, and improved the heat transfer. With the insertion of a twisted-tape, the maximum value of the pressure drop of the test section decreased more than 85%, the total amount of coke decreased more than 93%, and the wall temperature were significantly decreased. At the same axis position, the difference between the top and bottom wall temperatures decreased and the heat transfer coefficient improved compared with a plain tube. A well-predicted correlation of the Nusselt number was proposed.

关键词： Twisted-tape Hydrocarbon fuel Coke Heat transfer

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Effect of alkali metal cations modification on the acid/basic properties and catalytic activity of ZSM-5 in cracking of supercritical n-dodecane

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FUEL 2019年 243卷 155-161页

作者： Ji, Yajun Yang, Honghui Yan, Wei Xi An Jiao Tong Univ Dept Environm Sci & Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Alkali metal modified ZSM-5 (ZSM-5-M, M: Li, Na, K, Cs) was prepared by ion-exchange method. The ion-exchange of alkali metal cations with silanol group occurred along with hydrolysis of the Si-O(H)-Al, leading to increase of Lewis acid, decrease of strong and Bronsted acids. K+ and Cs+ were easier to exchange with proton of -OH compared with Na+ and Li+ due to their smaller hydrated radius, resulting in higher ion exchange capacity for ZSM-5-K and ZSM-5-Cs. Their catalytic performances in supercritical n-dodecane cracking were studied. The gas generation rates (GGR) and heat sinks under 550 degrees C and 4 MPa increased as following: ZSM-5-Cs < ZSM-5 < ZSM-5-K < ZSM-5-Li < ZSM-5-Na. The GGR and heat sink of ZSM-5-Na reached 60.3% and 2826 kJ kg(-1), respectively. Thus moderate attenuation of strong acid and enhancement of basic sites could enhance the catalytic performance in supercritical n-dodecane cracking. The selectivity for light alkene was enhanced and the coke was restrained due to the regulated acid-base properties, since decreasing strong acidic sites and increasing the basic sites could suppress the secondary reactions that consumed light alkene and generated coke.

关键词： ZSM-5 Alkali metal Acid property Catalytic cracking Coke Heat sink

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Light-enhanced thermochemical production of solar fuels from methane via nickel-based redox cycle

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FUEL 2023年第1期335卷

作者： Liu, Mingkai Zhang, Jinrui Yang, Tianlong Rao, Qiong Gai, Zhongrui Zhao, Jianxiong Pan, Ying Su, Dong Jin, Hongguang Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy Xian 710049 Peoples R China Chinese Acad Sci Inst Phys Beijing Natl Lab Condensed Matter Phys Beijing 100190 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Thermochemical methane reforming driven by solar energy is one of the efficient ways to store the renewable energy and to simultaneously reduce greenhouse gas emission. We report reaction reactivity of steam reforming of methane using nickel-based oxygen carrier driven by pure thermal heating and direct light irradiation in the same reactor. We find that the light-driven steam methane reforming system show improved conversion and reaction rate compared to that driven by pure thermal heating. We observed that illuminated NiO/NiAl2O4 achieved the same methane conversion rates and the H2 production rate comparable to those obtained on the same samples operated with only a thermal energy input, but at temperatures up to similar to 50 K lower. Based on in situ diffuse reflectance Infrared Fourier transform spectroscopy (DRIFTs) experiments, we postulate that light on the nickel oxide surface act to activate CH4 desorption and facilitate CHxO species evolution. By the combined effects of selection of chemical looping reactions and operation conditions, the solar-to-fuel efficiency of 16% was achieved. The results showcase the design of more energy-efficient chemical processes with a significant fraction of energy input provided in the form of direct sunlight irradiation as a potent pathway that can complement extremely high-temperature thermochemistry efforts in the quest for more efficient solar fuel production.

关键词： Thermochemical Methane Reforming Solar Fuel Photo-enhanced Thermochemistry

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Strengthening chlorobenzene catalytic degradation rate over LaxSr1-xMnO3?? by anchoring interfacial oxygen vacancy

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SEPARATION AND PURIFICATION TECHNOLOGY 2023年第1期311卷

作者： Li, Lu Zhao, Qi Fu, Shuangshuang Chen, Changwei Tian, Mingjiao Shi, Jianwen Ma, Mudi He, Chi Xi An Jiao Tong Univ Ctr Nanomat Renewable Energy Sch Elect Engn State Key Lab Elect Insulat & Power Equipment Xian 710049 Shaanxi Peoples R China Xian Univ Sci & Technol Coll Geol & Environm Xian 710054 Shaanxi Peoples R China Xi An Jiao Tong Univ Fac Elect & Informat Engn Xian 710049 Shaanxi Peoples R China Xian Univ Architecture & Technol Sch Environm & Municipal Engn Xian 710055 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Human Settlements & Civil Engn Xian 710049 Shaanxi Peoples R China

Surficial lattice oxygen in perovskite compounds is a common participant during chloroaromatic catalytic degradation. Herein, we proposed a facile oxygen vacancy construction strategy for preparing high active LaxSr1-xMnO3 +/-delta(LSMO) via NaBH4 treatment. Results reveal that LSMO composites are not only reduced by NaBH4 under mild condition, but also triggering a significant Sr segregation effect, which plays a key role in oxygen vacancy formation accounting to the electron donation from Sr to Mn acceptor and subsequent lattice oxygen activation. Moreover, the concentration of interfacial active oxygen species can be regulated by taming the La-Sr interaction with different Sr substitution proportions. The anchored oxygen vacancies (OVs) take advantage of electron capture or transfer and induce molecule oxygen into active oxygen species to react with chlorobenzene molecules, resulting in a preferential catalytic oxidation capacity. Amongst, reduced La0.5Sr0.5MnO3 +/-delta catalyst displays superior chlorobenzene destruction efficiency with 90% of which converted as low as 236 degrees C, which also exhibits a stable performance in long-time operation. However, the OVs would be refilled by H2O molecules and results in a weaker water resistance for OVs anchored catalyst. In summary, the annihilation of OVs is the most important factor for catalyst deactivation. The research offers a new avenue to construct interfacial oxygen species in perovskite oxides during the chlorobenzene deep oxidation process.

关键词： Anchoring oxygen vacancy Catalytic oxidation Chlorobenzene Sr segregation Perovskites

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Realization of multilocal gradient-doping PCN by alkali metal ion sustained release capsules for enhanced photocatalytic water splitting

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APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY 2023年第1期339卷

作者： Yan, Jiawei Fang, Wenjian Wei, Zhidong Chi, Jiasheng Chen, Mingxia Jiang, Zhi Jiang, Kun Shen, Shaohua Shangguan, Wenfeng Shanghai Jiao Tong Univ Res Ctr Combust & Environm Technol Shanghai 200240 Peoples R China Shanghai Jiao Tong Univ Coll Smart Energy Shanghai 200240 Peoples R China Yangzhou Univ Sch Elect & Energy Power Engn Yangzhou 225002 Peoples R China Shanghai Jiao Tong Univ Inst Fuel Cells Shanghai 200240 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The gradient-doping technique has been widely applied to induce an oriented built-in electric-field. However, it is still not efficient enough for charge mobility especially for particulate semiconductors, as the field is primarily in one direction from inner to surface. Here, we propose a multilocal gradient-doping technique that a nanocapsule is designed to store dopants and then release them into semiconductors nonuniformly. As an illustration, scattered pyrochlore-type K2Ta2O6 nanoparticles have been validated the capability of storing and releasing K+, which subsequently diffuse into the substrate PCN. Multi point-radiative gradient in K+ concentration, confined within the K2Ta2O6's vicinity, will construct several 3D potential wells which can not only accelerate the carrier separation but also offer more migration channels for both photo-induced electrons and holes to the surface. Consequently, the multilocal K+ gradient-doping PCN shows the longest carriers' lifetime and highest AQY (similar to 21.8% at 400 nm) compared with the other uniformly doping techniques.

关键词： Doping Photocatalysis Ion diffusion Potential well Charge transfer

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Experiment and Kinetics Studies on Ash Fusion Characteristics of Biomass/Coal Mixtures during Combustion

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ENERGY & FUELS 2019年第10期33卷 10317-10323页

作者： Lv, Yuan Niu, Yanqing Liang, Yang Liu, Siqi Wang, Denghui Hui, Shi'en Xi An Jiao Tong Univ Sch Energy & Power Engn Dept Thermal Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Cofiring of biomass and coal significantly reduces carbon emissions and alleviates ash-related problems of biomass. This study investigates the effect of the biomass/coal blending ratio on ash fusion characteristics through the ash fusion test, X-ray fluorescence, and X-ray diffractometry. Meanwhile, kinetic analysis of the ash fusion process was conducted to provide a new method and reading benchmark for obtaining precise and repeatable initial deformation temperature (IDT). Results showed that the IDT decreased with the increase of the biomass blending ratio because of the decrease of alumina content and the increase of potassium content. When the biomass blending ratio increased, the content of orthoclase and diopside at the low melting point increased, while the content of andalusite, quartz, and anhydrite at the high melting point decreased, resulting in the decline of IDT. Kinetic analysis indicated that with increasing biomass blending ratio, the activation energy of ash fusion reaction decreased, which is the essential reason for the decrease of IDT. Coal ash had an activation energy of 1144.67 ***(-1), while it decreased to 145.89 ***(-1) with an increased biomass blending ratio to 100%. Compared with the larger error (up to 60 degrees C) caused by visual reading on the morphological change of the triangle ash cone, kinetics calculation gave precise prediction with less error between 2 and 7 degrees C. As an optimal recommendation, the average shrinkage rate of height at 41% could be used as a reading benchmark for the determination of IDT in further study.

关键词： Potassium Activation energy Reaction products Biomass Coal

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Atomistic insights into the combustion mechanism and kinetic analysis of ethanol-ammonia blended: High-temperature pyrolysis and oxidation

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International Journal of Hydrogen Energy 2025年 148卷

作者： Xuan Yu Zhongquan Gao Yaling He Zuohua Huang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi' an 710049 PR China Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 PR China

Ammonia (NH 3 ) and ethanol (EtOH) have been extensively investigated as green, renewable liquid fuels. However, the mechanism through which high-temperature mixed combustion of ammonia and ethanol enhances reactivity, reduces ignition delay time, and improves combustion efficiency under optimal mixing conditions remains unclear. Therefore, ReaxFF-MD reactive force field molecular dynamics simulations were employed to investigate the pyrolysis and combustion characteristics of ethanol (EtOH) and ammonia (NH 3 ) fuel blends under various conditions, with a particular focus on their high-temperature pyrolysis and oxidation mechanisms, key intermediates, free radical formations, and final product distributions at varying equivalence ratios. High-temperature pyrolysis results indicate that EtOH first decomposes to generate OH radicals, which then attack NH 3 , contributing to its rapid decomposition. Meanwhile, the generated radicals further participate in secondary reactions, thereby accelerating the pyrolysis process. High-temperature oxidation results indicate that more free radicals (e.g., NH, OH, HO 2 , and O) participate in the mixed EtOH/NH 3 combustion, with OH radicals playing a key role in promoting the oxidation mechanism. Under oxygen-deficient conditions, the combustion rate shows a positive correlation with NH 3 concentration. Under the S 5 combustion condition (temperature: 3000 K, λ: 0.53, ρ: 0.203 g/cm 3 ), a greater number of radicals were involved in the combustion process, accelerating the combustion rate and reducing the ignition delay time. The findings suggest that moderate addition of NH 3 significantly enhances the combustion of EtOH, thereby offering a novel approach for the efficient utilization of the green fuel EtOH/NH 3 .

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Numerical study on thermal deformation behaviors of the single subassembly in sodium-cooled fast reactors based on Euler-Bernoulli beam theory

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NUCLEAR engineering AND DESIGN 2019年 345卷 28-39页

作者： Ma, Zhenhui Ma, Zehua Wu, Yingwei Wang, Mingjun Su, G. H. Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Due to the special geometry and compact arrangement of subassemblies in the sodium-cooled fast reactor, thermal deformation of the assemblies are easily triggered by uneven temperature distribution in the reactor core, which is negative for reactor safety. Therefore, it is necessary for researchers and engineers to conduct quantitative analysis towards thermal deformation behaviors of subassemblies, and furthermore, give reliable evaluation results on aftermath of the assembly thermal deformation. In the present study, thermal deformation analysis code FADAC, which was developed based on Euler-Bernoulli beam theory, was applied to make numerical investigation for thermal deformation behaviors of a single subassembly in sodium-cooled fast reactor. In order to preliminarily assess the capacity for thermal deformation, different temperature gradient conditions were considered and analyzed in detail for free bowing of the subassembly, furthermore, with the aid of numerical analysis for thermal axial forces and thermal bending moments, axial displacements and deflections were calculated finally. Besides, in order to predict the comprehensive results of the assembly deformation under both thermal load and mechanical load, restrained bowing were also analyzed for different temperature conditions. All of the simulation results were in good accordance with the experimental data. The present numerical research is of great significance to assembly deformation research in the sodium-cooled fast reactor, and will surely lay a solid foundation for deformation analysis towards multi-subassemblies.

关键词： Sodium-cooled fast reactor Thermal deformation Subassembly Deflection

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