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Thick exchange layer evaporation model with natural convection effect and evaporation experimental study for multicomponent droplet

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Chinese Journal of Aeronautics 2020年第7期33卷 1903-1918页

作者： Fang WANG Xiang GAO Yangchun XIAO Zhaoyang WU Jie JIN Aero-Engine Numerical Simulation Research Center School of Energy and Power EngineeringBeihang UniversityBeijing 100083China

In order to investigate the high-temperature evaporation characteristics of multicomponent liquid fuel,three kinds of blended fuel:n-heptane/n-decane/RP-3 aviation kerosene-ethanol were experimentally studied with and without forced ***,based on zerodiffusion and infinite diffusion concept,this study expanded Thick Exchange Layer evaporation model with natural convection effect(NC-TEL)to multicomponent liquid *** experimental results show that the droplet evaporation rate increases significantly with the increase of ambient *** temperature leads to more significant relationships between the composition ratio and the evaporation *** effect of forced convection is not obviously under the circumstance in this ***,the evaporation models were validated by experimental *** general,the new NC-TEL model behaves better than the Ranz-Marshall(R-M)model,and the prediction accuracy at high temperature is improved by 8%to 35%.In lower temperature conditions,the prediction of zero-diffusion NC-TEL model is better than the infinite diffusion NC-TEL *** high-temperature conditions,for n-heptane-ethanol droplet,the predictions of NC-TEL model are accurate,but for n-decane/RP-3 aviation kerosene-ethanol,the predictions are lower than experimental *** may be caused by the micro-explosion phenomenon and the Marangoni phenomenon.

关键词： Droplet Evaporation rate Multicomponent fuel evaporation model natural convection Suspended droplet experiment Thick exchange layer model

Lattice Boltzmann simulation of natural convection in open end cavity with inclined hot wall

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Applied Mathematics and Mechanics(English Edition) 2015年第4期36卷 523-540页

作者： M.NAZARI H.SHOKRI A.A.MOHAMAD Department of Mechanical Engineering Shahrood University of Technology Department of Mechanical Engineering Schulich School of EngineeringCentre for Environmental Engineering for Research and EducationUniversity of Calgary

natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method （LBM）. The physics of flow and energy transfer in open end cavities are addressed when the hot wall is inclined. The combination of the two topics （open cavity and inclined walls） is the main novelty of the present study. The effects of the angle of the hot inclined wall on the flow field and heat transfer are thoroughly investigated. The Prandtl number is fixed to 0.71 （air）. The Rayleigh number and the angle of the hot inclined wall are varied in the range of 10^4 to 10^6 and 60° to 85°, respectively. The results are presented for two different aspect ratios, i.e., A = 1 and 2. The results obtained with the LBM are also compared with those of the finite volume method （FVM）. The predicted results of the LBM conform to those of the FVM. The results show that by increasing the angle of the hot inclined wall and the aspect ratio of the cavity, the average Nusselt number decreases. The trend of the local Nusselt number on the inclined wall is also discussed.

关键词： lattice Boltzmann method (LBM) natural convection open end cavity,inclined wall

Numerical Analysis of Unsteady natural convection Flow and Heat Transfer in the Existence of Lorentz Force in Suddenly Expanded Cavity Using OpenFOAM

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Journal of Thermal Science 2020年第6期29卷 1513-1530页

作者： SINGH Ranjit J. GOHIL Trushar B. Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India

The present study reveals the significance of the magnetic field or Lorentz force on the unsteady natural convection flow and heat transfer in the suddenly expanded *** Lorentz force based magnetohydrodynamics(MHD)solver using electric potential formulation coupled with the energy equation by the means of Boussinesq approximation is developed in the open-source CFD tool *** unsteady flow is generated by the buoyancy force keeping the Rayleigh number(Ra)at 109,at the fixed Prandtl number(Pr)of *** effects of the magnetic field on the flow and heat transfer are explained for various orientations of magnetic field(Bx,B45,and By)in terms of Hartmann number(Ha=0,50,100,300 and 500).The increase in the magnetic field increases the strength of the Lorentz force,which regulates the flow pattern and suppresses down the unsteady nature of flow and heat transfer into the *** is perceived that the average Nusselt number decreases as the intensity of Bx and B45 magnetic field ***,for By magnetic field the average Nusselt number increases up to Ha of 100 as compared to the non-MHD case(Ha=0).The distribution of Lorentz force in the domain plays a significant role in the governing of the fluid flow and heat transfer.

关键词： OpenFOAM Lorentz force Boussinesq approximation natural convection

Simulation of natural convection under high magnetic field by means of the thermal lattice Boltzmann method

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Chinese Physics B 2009年第10期18卷 4083-4093页

作者：钟诚文解建飞卓从山熊生伟尹大川 National Key Laboratory of Aerodynamic Design and Research Northwestern Polytechnical University Faculty of Life Science Key Laboratory for Space Bioscience and Biotechnology Northwestern Polytechnical University

The thermal lattice Boltzmann method （TLBM）, which was proposed by J. G. M. Eggels and J. A. Somers previously, has been improved in this paper. The improved method has introduced a new equilibrium solution for the temperature distribution function on the assumption that flow is incompressible, and it can correct the effect of compressibility on the macroscopic temperature computed. Compared to the previous method, where the half- way bounce back boundary condition was used for non-slip velocity and temperature, a non-equilibrium extrapolation scheme has been adopted for both velocity and temperature boundary conditions in this paper. Its second-order accuracy coincides with the ensemble accuracy of lattice Boltzmann method. In order to validate the improved thermal scheme, the natural convection of air in a square cavity is simulated by using this method. The results obtained in the simulation agree very well with the data of other numerical methods and benchmark data. It is indicated that the improved TLBM is also successful for the simulations of non-isothermal flows. Moreover, this thermal scheme can be applied to simulate the natural convection in a non-uniform high magnetic field. The simulation has been completed in a square cavity filled with the aqueous solutions of KC1 （llwt%）, which is considered as a diamagnetic fluid with electrically low-conducting, with Grashof number Gr=4.64~104 and Prandtl number Pr----7.0. And three cases, with different cavity locations in the magnetic field, have been studied. In the presence of a high magnetic field, the natural convection is quenched by the body forces exerted on the electrically low-conducting fluids, such as the magnetization force and the Lorentz force. From the results obtained, it can be seen that the quenching efficiencies decrease with the variation of location from left, symmetrical line, to the right. These phenomena originate from the different distributions of the magnetic field strengths in the zone

关键词： thermal lattice Boltzmann method natural convection magnetization force Lorentzforce

Effect of induced magnetic field on natural convection in vertical concentric annuli

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Acta Mechanica Sinica 2012年第2期28卷 315-323页

作者： R.K.Singh A.K.Singh Department of Mathematics Central University of BiharPatnaIndia Department of Mathematics Banaras Hindu UniversityVaranasiIndia

In the present paper, we have considered the steady fully developed laminar natural convective flow in open ended vertical concentric annuli in the presence of a ra- dial magnetic field. The induced magnetic field produced by the motion of an electrically conducting fluid is taken into account. The transport equations concerned with the con- sidered model are first recast in the non-dimensional form and then unified analytical solutions for the velocity, induced magnetic field and temperature field are obtained for the cases of isothermal and constant heat flux on the inner cylin- der of concentric annuli. The effects of the various phys- ical parameters appearing into the model are demonstrated through graphs and tables. It is found that the magnitude of maximum value of the fluid velocity as well as induced magnetic field is greater in the case of isothermal condition compared with the constant heat flux case when the gap be- tween the cylinders is less or equal to 1.70 times the radius of inner cylinder, while reverse trend occurs when the gap between the cylinders is greater than 1.71 times the radius of inner cylinder. These fields are almost the same when the gap between the cylinders is equal to 1.71 times the radius of inner cylinder for both the cases. It is also found that as the Hartmann number increases, there is a flattening ten- dency for both the velocity and the induced magnetic field. The influence of the induced magnetic field is to increase the velocity profiles.

关键词： natural convection Isothermal Heat flux Skin-friction Induced magnetic field Magnetohydrody- namics

Characterization of size effect of natural convection in melting process of phase change material in square cavity

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Chinese Physics B 2021年第10期30卷 400-409页

作者： Shi-Hao Cao Hui Wang College of Civil Engineering Henan University of TechnologyZhengzhou 450001China School of Civil Engineering and Architecture Hainan UniversityHaikou 570228China

The accelerating effect of natural convection on the melting of phase change material(PCM)has been extensively ***,such an influence is directly dependent on the size and shape of domain in which phase change happens,and how to quantitatively describe such an influence is still *** the other hand,the simulation of natural convection process is considerably difficult,involving complex fluid flow in a region changing with time,and is typically not operable in *** overcome these obstacles,the present study aims to quantitatively investigate the size effect of natural convection in the melting process of PCM paraffin filled in a square latent heat storage system through experiment and simulation,and ultimately a correlation equation to represent its contribution is ***,the paraffin melting experiment is conducted to validate the two-dimensional finite element model based on the enthalpy ***,a comprehensive investigation is performed numerically for various domain *** results show that the melting behavior of paraffin is dominated by the thermal *** the melting time exceeds 50 s,a whirlpoor flow caused by natural convection appears in the upper liquid phase region close to the heating wall,and then its influencing range gradually increases to accelerate the melting of ***,its intensity gradually decreases as the distance between the melting front and the heating wall ***,it is found that the correlation between the total melting time and the domain size approximately exhibits a power *** the domain size is less than 2 mm,the accelerating effect of natural convection becomes very weak and can be ignored in ***,in order to simplify the complex calculation of natural convection,the equivalent thermal conductivity concept is proposed to include the contribution of natural convection to the total melting time,and an empirical correlation is given fo

关键词： phase change material natural convection size effect equivalent thermal conductivity

Simulation of inclined dendrites under natural convection by KKS phase field model based on CUDA

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中国铸造:英文版 2023年第5期20卷 432-442页

作者： Chang-sheng Zhu Tian-yu Li Bo-rui Zhao Cang-long Wang Zi-hao Gao College of Computer and Communication Lanzhou University of TechnologyLanzhou 730050China State Key Laboratory of Gansu Advanced Processing and Recycling of Non-Ferrous Metal Lanzhou University of TechnologyLanzhou 730050China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China Advanced Energy Science and Technology Guangdong Laboratory Huizhou 516000GuangdongChina

In this work,Al-4.5wt.%Cu was selected as the research object,and a phase field-lattice Boltzmann method(PF-LBM)model based on compute unified device architecture(CUDA)was established to solve the problem of low serial computing efficiency of a traditional CPU and achieve significant *** model was used to explore the evolution of dendrite growth under natural *** the study of the tip velocities,it is found that the growth of the dendrite arms at the bottom is inhibited while the growth of the dendrite arms at the top is promoted by natural *** addition,research on the inclined dendrite under natural convection was *** is observed that there is a deviation between the actual growth direction and the preferred angle of the inclined *** the increase of the preferred angle of the seed,the difference between the actual growth direction and the initial preferred angle of the inclined dendrite shows a trend of increasing at first and then *** the simulation area,the relative deflection directions of the primary dendrite arms in the top right corner and the bottom left corner of the same dendrite are almost counterclockwise,while the relative deflection directions of the other two primary dendrite arms are clockwise.

关键词： PF-LBM natural convection inclined dendrites CUDA

The efect of the couple stress parameter and Prandtl number on the transient natural convection flow over a vertical cylinder

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Acta Mechanica Sinica 2013年第5期29卷 649-656页

作者： H.P.Rani G.Janardhana Reddy Chang Nyung Kim Department of Mathematics National Institute of TechnologyWarangal-506004 AP India Department of Mechanical Engineering College of Advanced Technology (Industrial Liaison Research Institute)Kyung Hee UniversityGyeonggi-do 446-701 Korea

An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coupled governing equations is carried out with the aid of an unconditionally stable Crank-Nicolson type of numerical scheme. Numerical results for the steady-state velocity, temperature as well as the time histories of the skin-friction coefficient and Nus- selt number are presented graphically and discussed. It is seen that for all flow variables as the couple stress control parameter, Co, is amplified, the time required for reaching the temporal maximum increases but the steady-state decreases.

关键词： Couple stress fluid natural convection Vertical cylinder Finite difference method

Thermo-fluidic characteristics of natural convection in honeycombs:The role of chimney enhancement

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Science China(Technological Sciences) 2015年第8期58卷 1318-1327页

作者： YANG XiaoHu YAN HongBin WANG WenBin JIN LiWen LU TianJian ICHIMIYA Koichi Department of Building Environment and Energy Engineering School of Human Settlements and Civil EngineeringXi'an Jiaotong University MOE Key Laboratory for Multifunctional Materials and Structures Xi'an Jiaotong University School of Energy and Power Engineering Xi'an Jiaotong University State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi'an Jiaotong University Department of Mechanical Engineering University of Yamanashi

The natural convective heat transfer performance and thermo-fluidic characteristics of honeycombs with/without chimney extensions are numerically *** present numerical simulations are validated by the purposely-designed experimental measurements on honeycombs with/without *** agreement between numerical simulation and experimental measurement is *** influences of inclination angle and geometric parameters such as cell shape,streamwise and spanwise length are also numerically *** the increment in inclination angle,the overall heat transfer rate decreases for the honeycombs with/without *** honeycombs with the same void volume fraction but different cell shapes,there is little difference on the overall heat transfer *** enhance the natural convective heat transfer of honeycombs,these techniques including increasing the length of honeycomb in the streamwise/spanwise direction,increasing the thermal conductivity of hon-eycomb structure or adding a chimney extension may be helpful.

关键词： natural convection honeycomb adiabatic chimney inclination angle