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Experimental research on dryout point of flow boiling in narrow annular channels

Nuclear Science and Techniques 2006年第4期17卷 252-256页

作者： WU Ge-Ping QIU Sui-Zheng SU Guang-Hui JIA Dou-Nan LU Dong-Hua State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China Reactor Engineering Research Division Nuclear Power Institute of China Chengdu 610041 China

An experimental research on the dryout point of flow boiling in narrow annular channels under low mass flux with 1.55 mm and 1.05 mm annular gap, respectively, is conducted. Distilled water is used as working fluid and the range of pressure is limited within 2.04.0 MPa and that of mass flux is 26.069.0 kg·m(?2)·s(?1). The relation of critical heat flux (CHF) and critical qualities with mass flux and pressure are revealed. It is found that the critical qualities decrease with the increasing mass flux and increase with the increasing inlet qualities in externally heated annuli. Under the same conditions, critical qualities in the outer tube are always larger than those in the inner tube. The appearance of dryout point in bilaterally heated narrow annuli can be judged according to the ratio of qo/qi. key words: Narrow annular channel; flow boiling; Dryout point

关键词：临界热通量流动沸腾干燥核沸腾狭窄环形通道

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Numerical Stability and Accuracy of Contact Angle Schemes in Pseudopotential Lattice Boltzmann Model for Simulating Static Wetting and Dynamic Wetting

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Computer Modeling in engineering & Sciences 2023年第10期137卷 299-318页

作者： Dongmin Wang Gaoshuai Lin Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai200093China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application Suzhou University of Science and TechnologySuzhou215009China

There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity scheme(IVD scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the fluid layer density above the wall(MPB-C scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the weighted average density of surrounding fluid nodes(MPB-W scheme)and the geometric formulation scheme(GF scheme).But the numerical stability and accuracy of the schemes for wetting simulation remain unclear in the *** this paper,the numerical stability and accuracy of these schemes are clarified for the first time,by applying the five widely used contact angle schemes to simulate a two-dimensional(2D)sessile droplet on wall and capillary imbibition in a 2D channel as the examples of static wetting and dynamic wetting simulations respectively.(i)It is shown that the simulated contact angles by the GF scheme are consistent at different density ratios for the same prescribed contact angle,but the simulated contact angles by the PB scheme,IVD scheme,MPB-C scheme and MPB-W scheme change with density ratios for the same fluid-solid interaction *** PB scheme is found to be the most unstable scheme for simulating static wetting at increased density ratios.(ii)Although the spurious velocity increases with the increased liquid/vapor density ratio for all the contact angle schemes,the magnitude of the spurious velocity in the PB scheme,IVD scheme and GF scheme are smaller than that in the MPB-C scheme and MPB-W scheme.(iii)The fluid density variation near the wall in the PB scheme is the most significant,and the variation can be diminished in the IVD scheme,MPB-C scheme *** variation totally disappeared in the GF scheme.(iv)For the simulation of capillary imbibition,the MPB-C scheme,MPB-Wschem

关键词： Pseudopotential lattice Boltzmann model contact angle scheme static wetting dynamic wetting capillary imbibition

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Synergistic effect of oxygen species and vacancy for enhanced electrochemical CO_(2) conversion to formate on indium oxide

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eScience 2024年第3期4卷 134-141页

作者： Tengfei Ma Zihao Jiao Haoran Qiu Feng Wang Ya Liu Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

Indium-based oxides are promising electrocatalysts for producing formate via CO_(2) reduction reaction,in which*OCHO is considered the key ***,we identified that the*COOH pathway could be preferential to produce formate on In_(2)O_(3)of In/In_(2)O_(3) heterojunction due to the synergistic effect of oxygen species and ***,*CO_(2) and *COOH were observed on In_(2)O_(3) and related to formate production by in situ Raman *** theoretical calculations further demonstrated that the energy barrier of the*COOH formation on In_(2)O_(3) was decreased in the presence of oxygen vacancy,similar to or lower than that of the*OCHO formation on the In *** a result,a formate selectivity of over 90%was obtained on prepared In/In_(2)O_(3) heterojunction with 343±7mAcm^(-2) partial current ***,when using a Si-based photovoltaic as an energy supplier,10.11%solar-to-fuel energy efficiency was achieved.

关键词： Electrocatalytic CO_(2)reduction Formate In_(2)O_(3) Oxygen species Oxygen vacancy

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An investigation on heat transfer to supercritical water in inclined upward smooth tubes

An investigation on heat transfer to supercritical water in ...

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作者： Yin, Fei Chen, Ting-Kuan Li, Hui-Xiong National Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China National Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Within the range of pressures from 23 to 30 MPa, mass velocities from 600 to 1200 kg/(m 2 s), and heat fluxes from 200 to 600 kW/m 2 , experiments have been performed for an investigation on heat transfer to supercritical water in inclined upward smooth tubes with an inner diameter of 26 mm and an inclined angle of 20° from the horizon. The results indicated that heat transfer characteristics of supercritical water are not uniform along the circumference of the inclined tube. An increase in the mass velocity of the working fluid can decrease and even eliminate the non-uniformity. Properties of supercritical fluid acutely vary with the temperature near the pseudocritical point. While the ratio of the mass velocity to the heat flux exceeded 2.16 kg/(kWs), heat transfer enhancement occurred near the pseudocritical point;conversely, heat transfer deterioration occurred while the ratio of the mass velocity to the heat flux was lower than 2.16 kg/(kWs). As the pressure increased far from the critical pressure, the amount of deterioration decreased. Correlations of heat transfer coefficients of the forced-convection heat transfer on the top and bottom of the tube have been provided, and can be used to predict heat transfer coefficient of spirally water wall in supercritical boilers.

关键词： Pipe flow

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Comments on Three-point explicit compact difference scheme with arbitrary order of accuracy and its application in CFD

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Applied Mathematics and Mechanics(English Edition) 2009年第5期30卷 669-676页

作者：张红娜宇波王艺魏进家李凤臣 Beijing Key Laboratory of Urban Oil and Gas Distribution Technology China University of Petroleum School of Energy Science and Engineering Harbin Institute of Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The explicit compact difference scheme, proposed in Three-point explicit compact difference scheme with arbitrary order of accuracy and its application in CFD by Lin et al., published in Applied Mathematics and Mechanics （English Edition）, 2007, 28（7）, 943-953, has the same performance as the conventional finite difference schemes. It is just another expression of the conventional finite difference schemes. The proposed expression does not have the advantages of a compact difference scheme. Nonetheless, we can more easily obtain and implement compared with the conventional expression in which the coefficients can only be obtained by solving equations, especially for higher accurate schemes.

关键词： explicit compact difference scheme conventional finite difference scheme central difference scheme upwind difference scheme

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The Molecular Dynamics Simulation of Thermal Properties of R290 for Auto-cascade Refrigeration System

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Recent Patents on Mechanical engineering 2023年第5期16卷 345-358页

作者： Feng, Haocheng Liu, Zhenzhen Wang, Zilong Zhang, Hua School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

Background: Hydrocarbons are increasingly being considered as potential fourth-generation refrigerants due to their environmentally-friendly properties. However, accurate prediction and calculation of their thermal properties are essential for their industrial application. Objective: In this study, molecular dynamics simulations were performed to calculate the density, self-diffusion coefficient, viscosity and thermal conductivity of R290 at various operating temperatures of 200-240 K and pressures of 0.15 and 0.20 MPa, and 270-390 K and pressures of 1.5 and 2.0 MPa to veri-fy the feasibility of the methods. Methods: The equilibrium molecular dynamics simulation (EMD) approach was utilised. The soundness of the model and force field were verified by calculating the density of the system during the relaxation phase. In the output stage, the self-diffusion coefficient was calculated using the Einstein relation, while the viscosity and thermal conductivity were calculated using the Green-Kubo method. The simulation results were compared with the NIST data values, and the errors were analysed. Results: The density simulation results for R290 in the relaxation phase yielded an overall average absolute relative deviation (AARD) value of 3.97%. In the output stage, the simulation results for the transport coefficients of R290 showed AARD values of 7.68%, 6.60% and 11.04% for the self-diffusion coeffi-cient, viscosity, and thermal conductivity, respectively, compared to the NIST data values. Conclusion: These results indicate the feasibility of using molecular dynamics simulations to study the transport properties of hydrocarbon refrigerants. The findings also provide a foundation for future research on hydrocarbon refrigerant mixtures. Patent: The research presented in this work could serve as a valuable reference for future patent applications and technological innovations related to hydrocarbon refrigerants, particularly R290. This includes, but is not limited to, delive

关键词： Viscosity

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Numerical simulation on the frosting and heat transfer characteristics of plate-fin heat exchanger considering confinement effect

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Energy Storage and Saving 2022年第3期1卷 136-147页

作者： Xiaoling Yang Xue Liu Xiaojun Dong Yang Meng Yu Hou Tianwei Lai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

In refrigerating industry,frost commonly deposits on the confined cold surfaces of heat exchangers,which affects the heat transfer *** the confined flow path of the heat exchanger,the frosting at downstream is affected by the parameters from the *** this study,a numerical model considering the confinement effect has been proposed to predict frosting characteristics in plate-fin heat ***-diffusion equations for humid air and empirical correlations for local frost density are employed in the numerical *** behavior and heat transfer in the confined channel are investigated with different humid air parameters and cold surface *** results indicate that frost thickness in the confined channel is thicker than that in open space under the same inlet *** frost layer is thicker and fluffier along the confined *** addition,the air temperature difference between inlet and outlet of the confined channel enlarges with *** the same average temperature of upper and lower surfaces,the heat and mass transfer of frosting are enhanced with diminishing temperature difference of upper and lower *** such condition,frosting is mainly influenced by the cold surface with the lower temperature.

关键词： Heat exchanger Frosting Confined channel Numerical simulation Heat transfer

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Exergy Analysis of a Novel Chemical Looping Hydrogen Generation System Integrated with SOFC

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Journal of Thermal Science 2021年第1期30卷 313-323页

作者： ZHANG Xiaosong CHEN Zhewen CHEN Zhenbin LI Jinsong Mechanical and Electrical Engineering College Hainan UniversityHaikou 570228China Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing 102206China

In this paper,a novel system integrating chemical-looping hydrogen generation(CLH)system and solid oxide fuel cell(SOFC)has been *** new methane-fuelled energy system was investigated with energy balance and exergy *** produces the hydrogen as the fuel of the SOFC,and the Fe O and Fe3O4 are selected as the looping *** heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of *** to the cascade utilization of the fuel between the CLH and SOFC,the net efficiency of this novel system can achieve 62.8%considering CO_(2)separation,more than 10 percentage points higher than a methane reforming fuelled SOFC ***,by using the CLH to produce the hydrogen,the CO_(2)can be recovered without an energy *** the analysis of the graphical exergy,the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high *** novel system also has the advantage of CO_(2)capture without energy penalty,so this combined system is an advantaged method to accomplish the efficient utilization of methane.

关键词： chemical looping fuel cell exergy analysis

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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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Numerical prediction of spatio-temporal frosting patterns of curved surface considering varying working parameters

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Energy Storage and Saving 2023年第1期2卷 348-358页

作者： Xue Liu Xiaojun Dong Shaohang Yan Yu Hou Tianwei Lai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting *** this study,a numerical model is developed to predict the spatio-temporal frosting habits on curved surfaces in combination with the correlations of frost density and thermal *** the model,frost melting is *** verification,the frosting and heat transfer characteristics along the flow path are investigated under various structural and operating *** thickness along the path is mainly affected by the cooling surface temperature,while the heat and mass transfer rates are strongly correlated with the humidity *** proportions of latent heat and sensible heat are distributed more unevenly in parallel flow case than in counter flow *** deposition is facilitated by a smaller radius of curvature of the cooling *** uniform frosting characteristics along the path and smaller heat transfer obstruction are presented with a smaller length-to-height ratio of the flow path.

关键词： Frosting Numerical prediction Heat transfer Curved surface Varying parameter

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