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Experimental and Theoretical Study on CHF of a Ultra-Supercritical Circulating Fluidized Bed Boiler Water-Wall Tube at near-Critical Pressures

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Journal of Thermal Science 2023年第1期32卷 166-182页

作者： WANG Wenyu MA Zhan QING Hao NIE Chao YANG Haoyu BI Lingfeng YANG Dong PAN Wenxiao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China Department of Mechanical Engineering University of Wisconsin-Madison1513 University AveMadisonWI 53706USA

The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been *** particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°*** material of the tube is *** experimental investigation,the near critical pressure CHF test data of water are *** find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is *** the experimental data,a correlation function for the CHF is established via regression and machine *** established via machine learning greatly improved the regression *** study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type *** the development of the CHF model,the friction resistance coefficient is determined according to our test *** comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type *** calculation results of the model can provide reference for the optimal design of the USCFB boiler.

关键词： circulating fluidized bed critical heat flux near-critical pressure bubble crowding machine learning

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Experimental investigation of inflow-outflow asymmetry in induced-charge electro-osmosis

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Energy Storage and Saving 2024年第1期3卷 16-22页

作者： Lingqi Zhao Tianwei Lai Yingke Gao Shaohang Yan Mingzhe Liu Yu Hou State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China MOE Key Laboratory of Cryogenic Technology and Equipment Xi’an Jiaotong UniversityXi’an710049China

Induced-charge electro-osmosis(ICEO)is a research hotspot in bioengineering and analytical ***-outflow asymmetry of ICEO was reported in the existing literatures,but systematic study on this phenomenon is *** this experimental study,we found that in strong electric fields,not only the velocity magnitude but also the vortex positions of ICEO are asymmetrical along the inflow and outflow directions because of the pronounced non-uniform surface electrokinetic *** the inflow and outflow directions,the amplitudes of velocities are unequal,ICEO maximum velocity positions change depending on the electric field intensity and sodium chloride(NaCl)***,the distances between vortex centers are *** NaCl solution concentration of 0.001 mol⋅L^(-1),the outflow velocity almost *** asymmetry rises with the increasing electric field *** new discoveries can direct the application of microscale devices.

关键词： Induced-charge electro-osmosis Micro-particle image velocimetry Inflow-outflow asymmetry

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The evaporation of nanoscale sodium liquid film on the non-ideal nanostructure surface: A molecular dynamics study

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International Journal of Advanced Nuclear Reactor Design and Technology 2023年第1期5卷 1-8页

作者： Wang, Zetao Ye, Tianzhou Guo, Kailun Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Lab of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China

The nanoscale liquid sodium film inside the microporous wick structure is of great importance to understanding the evaporation mechanism of the sodium heat pipe. The novel optimized wick structure is made of several layers of special screen. The surface of each screen exhibits a nanostructure type. Some non-ideal nanostructures may result from experimental faults or limits. And they will have an effect on the evaporation of film. In the present study, molecular dynamics is adopted to investigate this effect. The simulation system consists of the liquid sodium film and the solid surface. The flat surface is set as the reference. Based on the three non-ideal shapes of deposition, the sinusoidal nanostructures, conical nanostructures, and spherical nanostructures are built. The results indicate that the evaporation is suppressed by the above nanostructure surfaces. The weakening effect is through three forms: the potential gradient of the liquid film is intensified and the evaporation difficulty is increased;the heat transfer in the solid-liquid contact region is impeded;the collision heat transfer inside the liquid film is affected due to the delay of the aggregation variation between liquid atoms. © 2023 Xi'an Jiaotong University

关键词： Heat pipes

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Multi-objective optimization research of open and closed air brayton cycle

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International Journal of Advanced Nuclear Reactor Design and Technology 2024年第1期6卷 21-31页

作者： Song, Meihui Qian, Yiran Leng, Yuyang Liu, Tao Yu, Lianyun Chen, Weixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China Reactor Engineering Technology Research Institute China Institute of Atomic Energy Beijing102413 China

Air Brayton cycle obtains the significant advantages of high efficiency, compact structure, easy medium requirement and so on, which is one of the most suitable choices for the mobile nuclear power conversion system. In this paper, system-component combined design method is used to establish the open and closed air Brayton cycle of diverse configurations. Based on performance and compactness targets, the multi-objective optimization is carried out to find the optimal design by nondominated sorting genetic algorithm II and entropy weight method. According to the analysis, the closed intercooling reheating recuperating cycle is the configuration with the best comprehensive performance, with cycle efficiency of 33.58 %, power density of 175.39 kW m−3 and power mass ratio of 68.60 kW t−1. The open simple recuperating cycle is the configuration with the smallest volume and mass, with cycle efficiency of 20.01 %, system volume of 6.56 m3 and system mass of 19.98 t. The closed intercooling recuperating cycle is the most balanced configuration, with cycle efficiency of 31.33 %, volume of 9.06 m3 and system mass of 24.97 t. Based on the optimal results, off-design performance analysis of different environmental conditions is also carried out for the configurations above. © 2024 Xi'an Jiaotong University

关键词： Brayton cycle

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Laminar Flame Instability of n-Hexane,n-Octane,and n-Decane in Spherical Expanding Flames

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Journal of Thermal Science 2024年第3期33卷 1189-1199页

作者： YIN Geyuan HU Erjiang LI Xiaotian LV Xin HUANG Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China United Automotive Electronic Systems Co. LtdShanghai201206China Chongqing Changan Automobile Co. Ltd.Chongqing401120China

This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and *** experiment was carried out in a constant volume combustion bomb to get the flame *** critical radius under different conditions was extracted using the image processing *** with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured ***,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this *** theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.

关键词： cellular instability equivalent cell radius critical Peclet number spherical flame

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Numerical simulation and structural optimization of spiral finned tube thermal energy storage

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International Journal of Advanced Nuclear Reactor Design and Technology 2023年第3期5卷 123-136页

作者： Ma, Yunfei Meng, Yu Li, Jingyu Chen, Weixiong Yang, Xiaohu Li, Shaodan Chong, Daotong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Wuhan Second Ship Design and Research Institute Wuhan430205 China

Thermal energy storage (TES) has emerged as a promising solution to enhance nuclear safety by passively removing decay heat during reactor shutdown and accidents, thus preventing overheating of the reactor core and protecting the integrity of containment barriers. The research of TES with different structures has broad application prospects and practical significance. In this study, the melting process of phase change material (PCM) in various TES structures was simulated by the numerical simulation method in two and three dimensions. The mechanism of gravity-driven natural convection enhancing heat transfer was revealed. The effects of different TES structures, fin pitch, fin height, and fin thickness on heat transfer performance were studied. The results showed that many vortices formed by liquid PCM are the main reason for enhancing the natural convection. Adding fins could greatly accelerate the heat storage process. The melting time of PCM in annular and spiral finned tube TES was 47.3% and 61.3% less than that in smooth tube TES, respectively. In the present study, the heat transfer effect was enhanced as the spiral fin pitch became small, the fin height increased and the fin thickness increased. Two opposite effects of fin structure on the natural convection were revealed: (1) positive effect provided by heat transfer enhancement and (2) negative effect produced by blockage. © 2023 Xi'an Jiaotong University

关键词： Phase change materials

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On the Intelligent Optimization of the Crevice Structure in a Rapid Compression Machine

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Journal of Thermal Science 2024年第3期33卷 1200-1215页

作者： GUO Qiang LIU Jie WU Yingtao WANG Hewu TANG Chenglong YU Ruiguang Department of Power Mechanical Engineering Beijing Jiaotong UniversityBeijing100044China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing100084China Beijing Key Laboratory of New Energy Vehicle Powertrain Technology Beijing100044China National International Science and Technology Cooperation Base Beijing Jiaotong UniversityBeijing100044China

In this study,the multi-objective intelligent optimization of the crevice structure in a rapid compression machine(RCM)is carried out based on the RCM simulation model modified with the KIVA-3V program.A multi-objective optimization simulation model of the crevice structure based on the large eddy simulation model coupled with the genetic algorithm NSGA-Ⅲis *** optimization parameters and seven optimization objectives are selected in the optimization *** results show that the genetic algorithm can quickly find the values of the optimized *** crevice volume ratio shows a trade-off relationship with the dimensionless temperature ratio T_(max)/T_(aver)and the tumble ratio.A larger crevice volume can reduce the flow of boundary layer cryogenic gas into the combustion chamber,thus improving the temperature *** addition,the crevice entrance width and the connecting channel length should be smaller,while the volume of the crevice main chamber should be larger,so as to sufficiently introduce the low-temperature gas of the boundary layer into the crevice and reduce their influence on the temperature field of the combustion *** the crevice volume accounts for10%of the total volume,the temperature uniformity of the combustor is significantly enhanced,and when the crevice volume accounts for 30.4%,there is almost no low-temperature vortex in the combustion chamber.

关键词： rapid compression machine adiabatic core area ignition delay period crevice structure

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Fabricating PdCe/OMS-2 catalysts with boosted low-temperature activity for toluene deep degradation

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Journal of Rare Earths 2023年第6期41卷 839-849,I0002页

作者： Lin Yue Zhihua Xu Minghua Hu Mingjiao Tian Mudi Ma Bijie Huang Chi He State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Industrial Fume and Dust Pollution Control Jianghan UniversityWuhan 430056China National Engineering Laboratory for VOCs Pollution Control Material&Technology University of Chinese Academy of SciencesBeijing 101408China

Porous cryptomelane-type octahedral molecular sieve(OMS-2)with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds(VOC)catalytic ***,complete conversion of arene over OMS-2 catalysts at relatively low temperature is still a challenge due to its limited crystal structure and inferior ***,a series of PdCe/OMS-2 catalysts with different Pd/Ce molar ratios was fabricated by a facile impregnation method and the physicochemical properties of which were extensively characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HR-TEM),B runauer-Emmett-Teller(BET)method,X-ray fluorescence(XRF),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction of H2(H2-TPR),Raman,In situ diffused reflectance infrared Fourier transform spectra(DRIFTS),and density functional theory(DFT)*** show that the total conversion of toluene can be achieved at 207℃ over PdCe2 with apparent activation energy as low as 62.6 kJ/*** strong synergistic effect between Pd and Ce remarkably boosts the catalytic activity of OMS-2,attributed to the abundant Mn^(3+)-O bands and active surface oxygen *** results reveal that oxygen vacancy can be formed over PdCe2 much easily than that of Pd/OMS-2 and Ce/OMS-2 with the oxygen vacancy formation energy of2.42,2.83 and 2.68 eV,*** increasing the Pd content cannot promote the catalytic activity although PdO is a critical active center in toluene *** vacancy attributed to the integrative effect of Pd,Ce and Mn species plays a promine nt role over prepared catalysts in toluene activation *** findings reported in this work showed new insights into the designing of highly efficient OMS-2catalysts for VOC deep oxidation by tuning oxygen vacancy concentration.

关键词： PdCe/OMS-2 Toluene Catalytic oxidation Oxygen vacancy Rare earths

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NUMERICAL SIMULATION OF SINGLE/TWO-PHASE flow IN A STRATIFIED POROUS BED 31

NUMERICAL SIMULATION OF SINGLE/TWO-PHASE FLOW IN A STRATIFIE...

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2024 31st International Conference on Nuclear Engineering, ICONE 2024

作者： Bouloudenine, Aimad Li, Liangxing Xiang, Zutao Shi, Shang Bakar, Muhammad Abu Xi’an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xianning West Road 28 Xi’an City710049 China

ISBN: (纸本)9780791888292

This study investigates the coolability of debris beds formed from Fuel-Coolant Interactions (FCI) within nuclear reactors, a critical safety concern when cooling systems fail, leading to significant core melting in light-water reactors. The research focuses on understanding the flow dynamics within two-layer stratified porous beds, which develop from the mixture of corium and coolant, particularly around the interface between layers. Using ANSYS Fluent software, numerical simulations were conducted to estimate velocity profiles and pressure drops across a stratified porous structure. The Euler-Euler two-fluid model was employed alongside the k-ω-based Shear Stress Transport (SST) turbulence model to separately model turbulence for each phase. The results reveal that lateral flow dynamics are significant as fluids traverse through the porous media, affecting pressure drops across layers with varying permeabilities. Specifically, the pressure drops across the lower-permeability layer decrease while that across the higher-permeability layer increases, highlighting the influence of lateral flows between layers of different particle sizes due to variations in porosity. This lateral flow is most likely formed during the initial stages of fluid movement through the bed. The study underscores the importance of understanding these flow characteristics for both single/two-phase flow to enhance the safety and design of nuclear reactors by improving debris bed coolability predictions. Copyright © 2024 by ASME.

关键词： Computational fluid dynamics

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Research and development of helium-xenon Brayton cycle technology:A review

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National Science Open 2024年第6期3卷 188-218页

作者： Weixiong Chen Meihui Song Yiran Qian Hongxing Yu Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Key Laboratory of Nuclear Reactor System Design Technology Nuclear Power Institute of ChinaChengdu 610200China

Helium-xenon Brayton cycle systems have significant potential as the energy conversion system for small-scale reactors in remote land,deep-sea,and space applications due to a range of advantages,including high cycle efficiency,compact system structures,and chemical *** objective of this review is to provide a comprehensive understanding of the helium-xenon Brayton cycle system based on the projects and ***,the basic information and development history are introduced,and a series of typical designs are ***,the system configurations,cycle parameter analysis and optimization are ***,the key components are classified,such as turbine,compressor,and heat ***,the dynamic processes and control strategies are introduced in different ***,the deficiency and prospect of current research are *** review covers the representative helium-xenon Brayton cycle systems,which could provide a reference for promoting the development of energy conversion systems.

关键词： helium-xenon Brayton cycle cycle analysis heat exchanger dynamic research

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