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A Review on Thermal Design of Liquid Droplet Radiator System

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 state-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 *** state-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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Numerical simulation of local and global mixing/segregation characteristics in a gas–solid fluidized bed

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Chinese Journal of Chemical engineering 2022年第4期35卷 72-86页

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

Researches on solids mixing and segregation are of great significance for the operation and design of fluidized bed *** this paper,the local and global mixing and segregation characteristics of binary mixtures were investigated in a gas–solid fluidized bed by computational fluid dynamics-discrete element method(CFD-DEM)coupled approach.A methodology based on solids mixing entropy was developed to quantitatively calculate the mixing degree and time of the *** mixing curves of global mixing entropy were acquired,and the distribution maps of local mixing entropy and mixing time were also *** comparing different operating conditions,the effects of superficial gas velocity,particle density ratio and size ratio on mixing/segregation behavior were *** showed that for the partial mixing state,the fluidized bed can be divided into three parts along the bed height:complete segregation area,transition area and stable mixing *** areas showed different mixing/segregation *** gas velocity promoted the local and global mixing of binary *** increase in particle density ratio and size ratio enlarged the complete segregation area,reduced the mixing degree and increased the mixing time in the stable mixing area.

关键词： Discrete element method Solids mixing Binary mixtures Fluidized bed

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Semiempirical equations of state of H_(2)O/CO_(2) binary mixtures in graphite nanoslits

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 83-92页

作者： Haoxuan Li Bin Zhao Chengzhen Sun Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The existence of confining walls limits the prediction accuracy of nanoconfined fluids using macroscopic equations of state(EOSs);moreover,appropriate EOSs for multicomponent mixture fluids in nanoconfined spaces are ***,we derive the EOS of multicomponent mixture fluids confined in nanospaces at high temperatures and pressures,mainly considering the nanoconfinement effect and the competitive adsorption effect between different ***,the EOSs are validated through comparison with the molecular dynamics-simulated Pv T data of CO_(2)/H_(2)O mixtures in graphite *** consider the above effects,we derive two EOSs via two modeling methods:EOS I is obtained through modification of the actual component occupation volume in the Peng-Robinson equation of state(PR EOS)by fitting the binary component interaction coefficient and the number of adsorbed molecules according to a selectivity coefficient,while EOS II is obtained by considering the decreased pressure of the fluids in PR EOS by adding an attractive term between components and *** the simulation results as a benchmark,the two EOSs exhibited good prediction accuracies under low CO_(2) concentrations,and generally,EOS II was more accurate than EOS *** study fills the gap in the EOSs of nanoconfined mixture fluids,and the obtained equations can help to further describe the thermodynamic properties of confined mixture fluids.

关键词： confined fluid mixtures equation of state nanoconfined spaces molecular dynamics simulation

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Numerical investigation on characteristics of interfacial wave of liquid film in gas-liquid two-phase flow using OpenFOAM

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Chinese Journal of Aeronautics 2024年第2期37卷 233-248页

作者： Xiaoqi MA Yueshe WANG Jiaming TIAN State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Liquid film cooling as an advanced cooling technology is widely used in space *** operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket *** stability of liquid film is mainly determined by the characteristics of interfacial wave,which is rarely investigated right *** to improve the stability of thin film has become a hot *** view of this,an advanced model based on the conventional Volume of Fluid(VOF)model is adopted to investigate the characteristics of interfacial wave in gas-liquid flow by using OpenFOAM,and the mechanism of formation and development of wave is revealed intuitively through numerical *** effects from gas velocity,surface tension and dynamic viscosity of liquid(three factors)on the wave are studied *** can be found that the gas velocity is critical to the formation and development of wave,and four modes of droplets generation are illustrated in this ***,a gas vortex near the gas-liquid interface can induce formation of wave easily,so changing the gas vortex state can regulate formation and development of ***’s more,the change rules of three factors influencing on the interfacial wave are obtained,and the surface tension has a negative effect on the formation and development of wave only when the surface tension coefficient is above the critical value,whereas the dynamic viscosity has a positive effect in this ***,the maximum height and maximum slope angle of wave will level off as the gas velocity ***,the maximum slope angle of wave is usually no more than 38°,no matter what happens to the three factors.

关键词： Interfacial wave Gas-liquid Two-phase flow VOF model OpenFOAM

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Development of a fan-stirred constant volume combustion chamber and turbulence measurement with PIV

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Frontiers in Energy 2022年第6期16卷 973-987页

作者： Haoran ZHAO Jinhua WANG Xiao CAI Zhijian BIAN Hongchao DAI Zuohua HUANG State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

A fan-stirred combustion chamber is developed for spherically expanding flames,with P and T up to 10 bar and 473 K,*** characteristics are estimated using particle image velocimetry(PIV)at different initial pressures(P=0.5-5 bar),fan frequencies(ω=0-2000 r/min),and impeller diameters(D=100 and 114 mm).The flame propagation of methanol/air is investigated at different turbulence intensities(u′=0-1.77 m/s)and equivalence ratios(f=0.7-1.5).The results show that u′is independent of P and proportional toω,which can be up to 3.5 m/s at 2000 r/min.L_(T)is independent of P and performs a power regression withω*** turbulent field is homogeneous and isotropic in the central region of the chamber while the inertial subrange of spatial energy spectrum is more collapsed to-5/3 law at a high Re_(T).Compared to laminar expanding flames,the morphology of turbulent expanding flames is wrinkled and the wrinkles will be finer with the growth of turbulence intensity,consistent with the decline of the Taylor scale and the Kolmogorov *** determined S_(L)in the present study is in good agreement with that of previous *** S_(L)and S_(T)of methanol/air have a non-monotonic trend with f while peak S_(T)is shifted to the richer side compared to S_(L).This indicates that the newly built turbulent combustion chamber is reliable for further experimental study.

关键词： fan-stirred combustion chamber turbulence characteristics particle image velocimetry(PIV) methanol turbulent expanding flames

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A numerical investigation on heat transfer characteristics of a particle cluster in fluid with variable properties

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Particuology 2024年第11期94卷 327-344页

作者： Xiaoyu Li Huibo Wang Bowei Zhang Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710049China

This work investigates the heat transfer characteristics of particle clusters under the effects of the complex properties of supercritical water(SCW).It analyzes the heat transfer characteristics of sub-particles and the average heat transfer characteristics of particle *** results reveal a phenomenon of shifting positions of high specific heat *** led to variations in the dimensionless heat transfer coefficient ***,the results indicate that as the heat transfer process strengthens,the effects of variations in property distribution on heat transfer tends to *** on this conclusion,the effects of variations in property distribution on heat transfer are categorized into Stable Effects Region and Non-Stable Effects *** utilizing the principles of fluid flow-heat transfer coupling and similarity,a heat transfer prediction model for particle clusters in SCW is established.

关键词： Heat transfer Supercritical water Particle cluster Modeling

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Numerical Investigation on the Heat Transfer Characteristics of Supercritical Water in a Non-Uniformly Heated Tube for a Supercritical CFB Boiler

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Journal of Thermal Science 2023年第5期32卷 1807-1818页

作者： DU Xiaocheng SONG Yuanyuan XIANG Yuxuan ZHOU Yanjun WANG Aoyu YANG Dong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical *** Shear Stress Transport(SST)k-ωmodel was adopted for describing *** operating parameters are chosen according to a 660 MW ultra-supercritical CFB *** heat transfer performances under different operating parameters,such as boiler load,flow direction and heat flux distribution are *** temperature and heat flux on inner wall varies along the circumference and show symmetric *** overall heat transfer performances at each cross section are better than the local heat transfer performance of midpoint of heating *** direction has a great influence on heat transfer performance;it changes the radial distribution of axial velocity and then affects the turbulence ***,upward flow condition shows a better heat transfer *** heat flux improves both the overall and local heat transfer *** the heat flux area is not conducive to the overall heat transfer,but does not affect the local heat transfer at the midpoint of heating ***,a new correlation is fitted based on the simulated results of supercritical water heat transfer with circumferential non-uniform heat flux distributions.

关键词： supercritical CFB boiler circumferential non-uniform heat flux numerical simulation heat transfer correlation

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Optimization of cold-end system of thermal power plants based on entropy generation minimization

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Frontiers in Energy 2022年第6期16卷 956-972页

作者： Yue FU Yongliang ZHAO Ming LIU Jinshi WANG Junjie YAN State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Cold-end systems are heat sinks of thermal power cycles,which have an essential effect on the overall performance of thermal power *** enhance the efficiency of thermal power plants,multi-pressure condensers have been applied in some large-capacity thermal power ***,little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be ***,the design optimization methods of coldend systems with single-and multi-pressure condensers are developed based on the entropy generation rate,and the genetic algorithm(GA)is used to optimize multiple *** parameters,including heat transfer area of multi-pressure condensers,steam distribution in condensers,and cooling water mass flow rate,are optimized while considering detailed entropy generation rate of the cold-end *** results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is ***,the economic performance can be improved with the adoption of the multi-pressure cold-end *** compared with the single-pressure cold-end system,the excess revenues gained by using dual-and quadruplepressure cold-end systems are 575 and 580 k$/a,respectively.

关键词： cold-end system entropy generation minimization optimization economic analysis genetic algorithm(GA)

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Large Eddy Simulation Study on the Turbulence and Flame Characteristics under Analogical Integral Scale and Turbulence Intensity of Turbulent Premixed Flames

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Journal of Thermal Science 2023年第1期32卷 488-501页

作者： WEI Xutao WANG Jinhua ZHANG Meng HUANG Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Bunsen burner is a typical geometry for investigating the turbulence-flame *** most experimental studies,only turbulence intensity u′and integral scale l0 are used to characterize the turbulent flow field,regardless of the perforation geometry of perforated ***,since the geometry influences the developing process and vortex broken,the plate geometry has to be considered when discussing the flame-turbulence *** order to investigate conditions at the same l0 and u′using different geometries,large eddy simulation of CH_(4)/air flames with dynamic TF combustion model was *** model validation shows good agreement between Large Eddy Simulation(LES)and experimental *** the non-reacting flows,the Vortex Stretching of circular-perforated plate condition is always larger than that of slot-perforated plate condition,which comes from the stresses in the flow fields to stretch the vorticity *** reacting flows,at the root of the flame,the Vortex Stretching plays a major role,and the total vorticity here of circular-perforated plate condition is still larger(53.8%and 300%larger than that of the slot-perforated plate at x/D=0 and x/D=2.5,respectively).More small-scale vortex in circular-perforated plate condition can affect and wrinkle the flame front to increase the Probability Density Function(PDF)at large *** 3D curvature distributions of both cases bias to negative *** negative trend of curvatures at the instant flame front results from the Dilatation ***,the value of the Vortex Stretching and the Dilatation at the flame front of circular-perforated plate condition is obviously larger.

关键词： large eddy simulation integral scale turbulence intensity vorticity flame curvature

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Assisting effect of Al_(2)O_(3) on MnO_(x) for NO catalytic oxidation

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Green Energy & Environment 2021年第6期6卷 903-909页

作者： Denghui Wang Hui Li Qi Yao Shien Hui Yanqing Niu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an710049China

Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst *** performance of the catalysts was tested to study the effect of support on Mn-based catalyst *** of the catalysts followed as Mn_(0.4)/Al>Mn_(0.2)/Al>Mn_(0.4)/Ti>Mn_(0.2)/Ti>MnO_(x)>Al_(2)O_(3)on the whole,indicating the synergism of MnO_(x)and Al_(2)O_(3)for NO catalytic *** were analyzed according to characterization *** oxygen on catalyst rather than lattice oxygen was detected as the active oxidizer for NO *** catalyst support,Al_(2)O_(3)provided more sites to carry surface adsorbed oxygen than TiO_(2),resulting in the presence of more active oxygen on Mn O_(x)/Al_(2)O_(3)than on MnO_(x)/TiO_(2).Moreover,MnO_(x)/Al_(2)O_(3)possessed high surface area and pore volume,which greatly benefited the adsorption of NO on catalyst and further favored the oxidation of NO by active *** these advantages helped Mn_(0.4)/Al exhibited the best catalytic efficiency.

关键词： NO catalytic oxidation MnO_(x)/Al_(2)O_(3) NO_(2) Active oxygen

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