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natural convection of a Power-Law Nanofluid in a Square Cavity with a Vertical Fin

Fluid Dynamics & Materials Processing 2024年第9期20卷 2091-2108页

作者： Amira M’hadbi Mohammed El Ganaoui Haïkel Ben Hamed Amenallah Guizani Khalid Chtaibi LERMAB Department of Transition and Energy Efficiency ProfessionsIUT H Poincaréde LongwyUniversity of LorraineLongwy54400France LPT Center for Energy Research and Technologies(Borj Cedria2084)University of Tunis El ManarTunis1068Tunisia LTI Department of Mechanical Engineering and ProductionIUTUniversity of Picardie Jules-VerneAmiens80025France

The behavior of non-Newtonian power-law nanofluids under free convection heat transfer conditions in a cooled square enclosure equipped with a heated fin is investigated *** particular,the impact of nanofluids,composed of water and Al_(2)O_(3),TiO_(2),and Cu nanoparticles,on heat transfer enhancement is *** aim of this research is also to analyze the influence of different parameters,including the Rayleigh number(Ra=10^(4)-10^(6)),nanoparticle volume fraction(φ=0%-20%),non-Newtonian power-law indexes(n=0.6-1.4),and fin dimensions(Ar=0.3,0.5,and 0.7).Streamlines and isotherms are used to depict flow and related heat transfer *** indicate that thermal performance improves with increasing Rayleigh number,regardless of the nanoparticle type or nanofluid rheological *** suggests that the buoyancy force has a significant impact on heat transfer,particularly near the heat *** Nusselt number is more sensitive to variations in Cu nanoparticle volume fractions compared to Al₂O₃and TiO₂.Moreover,the average Nusselt numbers for power-law nanofluids with n1)are greater(smaller)than for Newtonian fluids due to the decrease(increase)in viscosity with increasing(decreasing)shear rate,at the same values of Rayleigh number Ra owing to the amplification(attenuation)of the convective ***,the most substantial enhancement is observed with Cu-water shear-thinning nanofluid,where the Nusselt number increases by 136%when changing from Newtonian to shear thinning behavior and by 154.9%when adding 16%nanoparticle volume ***,an even larger increase of 57%in the average Nusselt number is obtained on increasing the fin length from 0.3 to 0.7.

关键词： Heat transfer nanofluid non-Newtonian fluid natural convection

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Enhanced natural convection for Accelerating Melting of Phase Change Material in Cellular Structure through Inserting Fin

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Journal of Thermal Science 2024年第2期33卷 548-563页

作者： KONG Dekui ZHANG Yongcun LIU Shutian State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian116024China

The design of thermal conductivity enhancers(TCE) is quite critical to overcoming the disadvantage of the poor thermal conductivity of phase change materials(PCM).The main contribution of this study is firstly to discuss how to actively enhance natural convection of the melted PCM in cellular structure by the fin formed in the structure under the condition of the same metal mass,apart from simultaneously improving heat conduction,which can boost the heat transfer ***,a tailored hybrid fin-lattice structure(HFS) as TCE is designed and fabricated by additive manufacturing(AM).A two-equation numerical method is applied to study the heat transfer of the PCM,and its feasibility is validated with the experimental *** numerical results indicate that enhanced natural convection and improved heat conduction can be obtained simultaneously when a well-designed fin is embedded into a lattice *** enhanced natural convection results in the improved melting rate and the decreased wall temperature;e.g.,the complete melting time and the wall temperature are reduced by 11.6% and 19.7%,respectively,because of the fin for metal ***,the parameters of HFS including the porosity,pore density,and fin dimension have a great impact on the heat *** enhancement effect of the fin for HFS on the melting rate of the PCM increases as the thermal conductivity of the base material *** example,when the fin is introduced into the lattice structure,the complete melting time is reduced by 24.1% for metal *** summary,this study enables us to obtain a good understanding of the mechanism of the heat transfer and provides necessary experimental data for the structural design of HFS fabricated by AM.

关键词： natural convection heat transfer enhancement phase change material additive manufacturing hybrid fin-lattice structure

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Updated Lagrangian Particle Hydrodynamics (ULPH)Modeling of natural convection Problems

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Computer Modeling in Engineering & Sciences 2024年第10期141卷 151-169页

作者： Junsong Xiong Zhen Wang Shaofan Li Xin Lai Lisheng Liu Xiang Liu Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of TechnologyWuhan430070China Department of Engineering Structure and Mechanics Wuhan University of TechnologyWuhan430070China Department of Civil and Environmental Engineering The University of CaliforniaBerkeleyCA 94720USA

natural convection is a heat transfer mechanism driven by temperature or density differences,leading to fluid motion without external *** occurs in various natural and engineering phenomena,influencing heat transfer,climate,and fluid mixing in industrial *** work aims to use the Updated Lagrangian Particle Hydrodynamics(ULPH)theory to address natural convection *** Navier-Stokes equation is discretized using second-order nonlocal differential operators,allowing a direct solution of the Laplace operator for temperature in the energy *** numerical simulations,including cases such as natural convection in square cavities and two concentric cylinders,were conducted to validate the reliability of the *** results demonstrate that the proposed model exhibits excellent accuracy and performance,providing a promising and effective numerical approach for natural convection problems.

关键词： Updated Lagrangian particle hydrodynamics(ULPH) natural convection meshless methods higher order Laplacian model

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natural convection of an alumina-water nanofluid inside an inclined wavy-walled cavity with a non-uniform heating using Tiwari and Das' nanofluid model

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Applied Mathematics and Mechanics(English Edition) 2018年第10期39卷 1425-1436页

作者： M.A.SHEREMET R.TRIMBITAS T.GROSAN2 I.POP Laboratory on Convective Heat and Mass Transfer Tomsk State UniversityTomsk 634050Russia Department of Mathematics Babes-Bolyai UniversityCluj-Napoca 400084Romania

The present study is devoted to numerical analysis of natural convective heat transfer and fluid flow of alumina-water nanofluid in an inclined wavy-walled cavity under the effect of non-uniform heating. A single-phase nanofluid model with experimental correlations for the nanofluid viscosity and thermal conductivity has been included in the mathematical model. The considered governing equations formulated in dimensionless stream function, vorticity, and temperature have been solved by the finite difference method. The cavity inclination angle and irregular walls(wavy and undulation numbers)are very good control parameters for the heat transfer and fluid flow. Nowadays, optimal parameters are necessary for the heat transfer enhancement in different practical applications. The effects of the involved parameters on the streamlines and isotherms as well as on the average Nusselt number and nanofluid flow rate have been analyzed. It has been found that the heat transfer rate and fluid flow rate are non-monotonic functions of the cavity inclination angle and undulation number.

关键词： wavy cavity natural convection Al2O3-water nanofluid non-uniform heating numerical result

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natural convection heat transfer of molten salt in a single energy storage tank

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Science China(Technological Sciences) 2016年第8期59卷 1244-1251页

作者： LU YuanWei YU Qiang DU WenBin WU YuTing MA ChongFang Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of Education of China College of Environmental and Energy Engineering Beijing University of Technology Beijing 100124 China

Heat transfer in molten salt in a cylinder tank is studied via simulation and experiment to obtain its natural convection heat transfer in a single energy storage tank. Simulation and experimental results show that the natural convection heat transfer of water in a cylinder tank fits well with Garon＇s correlation. However, significant deviations occur when Garon＇s correlation is used to predict the natural convection heat transfer of molten salt because of its high viscosity and low thermal conductivity. However, the simulated data of the natural convection heat transfer of molten salt fit well with those of the experimental results Thus, a correlation that considers the effect of variable physical properties is proposed in this study to predict the natural con- vection heat transfer of molten salt. The deviation of the present data from the proposed correlation is less than ＋20%. The re- sults of this study can serve as a basis for the design of single energy storage tanks.

关键词： tank natural convection numerical methods experiment molten salt

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natural convection in a Horizontal Cylinder with Partial Heating: Energy Efficiency Analysis

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Journal of Thermal Science 2020年第6期29卷 1531-1550页

作者： MAZGAR Akram JARRAY Khouloud HAJJI Fadhila BEN NEJMA Faycal The Higher Institute of Applied Sciences and Technology of Sousse University of SousseTunisia-Ibn Khaldun StreetTaffala City4003 SousseTunisia The Preparatory Institute for Engineering Studies of Monastir University of MonastirTunisia-Rue Ibn El Jazzar5019 MonastirTunisia

The current study reports a numerical analysis of free convection of air in an isothermal horizontal cylinder,cooled and heated at different wall *** heater sizes are discussed in this *** first heated zone is spread across one-quarter of the sidewall;the second is uniformly distributed over the half of the wall and the third active wall covers three-quarters of the *** various locations are considered and examined for each active zone of the *** computation is carried out for Rayleigh number ranging from 102 to *** results characterizing heat transfer and flow features are achieved using an iterative model developed in COMSOL *** effect of Rayleigh number on heat transfer and fluid flow characteristics within the cavity are *** attention is paid to the influence of heater location and heater size on energy *** is found that the mean Nusselt number and dimensionless velocity increase when increasing the Rayleigh ***,the optimal level of energy efficiency is achieved if the heating zone is centered at the upper part of the cylinder,regardless of the heater *** is also shown that the optimal configuration providing higher energy efficiency is obtained when three-quarters of the sidewall are locally heated,and more precisely,if the active zone is centered at the top of the cylinder.

关键词： natural convection cylinder partial heating energy efficiency Rayleigh number

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natural convection effects on TNT solidification inside a shaped charge mold

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Defence Technology（防务技术） 2022年第9期18卷 1653-1661页

作者： Cigdem Susantez Aldelio B.Caldeira Bruna R.Loiola Trakya University Engineering FacultyMechanical Engineering DepartmentEdirne22030Turkey Management and Technological Innovation Agency Brazilian ArmyRio de Janeiro23020-470Brazil Military Institute of Engineering Mechanical Engineering DepartmentRio de Janeiro22290-270Brazil

High Explosive Anti-Tank(HEAT) warheads and ammunitions are frequently produced by explosive casting inside an axis-symmetric mold with an inverted conical geometry in the basis. In order to prevent manufacturing defects, the solidification process must be controlled. In this study, a dimensionless solidification model has been proposed to investigate the heat transfer considering the natural convection inside the liquid explosive and the numerical simulations were performed by using COMSOL Multiphysics and Modeling Software, employing trinitrotoluene(TNT) thermophysical properties. The effect of three different boundary conditions on the top of the mold have been evaluated: convection, adiabatic and isothermal. It has been observed that solidification process was faster for convection case and slower for isothermal case, while an intermediary total solidification time value was found for adiabatic ***, liquid explosive was completely surrounded by solid explosive during the solidification process for convection case and also for adiabatic case through the end of the process. Otherwise, it was not observed for isothermal case. The natural convection effects promoted a vortex inside the liquid explosive, accelerating the heat transfer process. It has been concluded that isothermal mold top boundary condition should be preferred to prevent manufacturing defects, avoiding high thermal stress.

关键词： Solidification natural convection Explosive Dimensionless model Anti-Tank ammunition

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natural convection of SiO_2-water nanofluid in square cavity with thermal square column

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 585-602页

作者： Xiaopeng XIONG Sheng CHEN Bo YANG State Key Laboratory of Coal Combustion Huazhong University of Science and Technology Institute for Modelling and Simulation in Fluodynamics Nanoscience and Industrial Mathematics "Gregorio Millan Barbany"Universidad Carlos III de Madrid Faculty of Engineering The University of NottinghamUniversity Park

A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nanofluids have not been revealed comprehensively, especially on entropy generation. To deepen insight into this important field, the natural convection of the SiO2-water nanofluid in a square cavity with a square thermal column is studied numerically in this study. The effects of the thermal column temperature （T = 0.0, 0.5, 1.0, 1.5）, the Rayleigh number （ranging from 103 to 106）, and the volume fraction of the nanoparticle （varying from 0.01 to 0.04） on the fluid flow, heat transfer, and entropy generation are investigated, respectively. It is found that, no matter at a low or high Rayleigh number, the volume fraction of the nanoparticle shows no considerable effects on the flow field and temperature field for all the temperatures of the thermal column. With an increase in the volume fraction, the mean Nusselt number increases slightly. At the same time, it is found that, with an increase in the temperature of the thermal column, the average Nusselt number gradually decreases at all values of the Rayleigh number. Meanwhile, it is found that, at a high Rayleigh number, the heat transfer mechanism is the main parameter affecting the increase in the total entropy generation rather than the volume fraction. In addition, no matter at a high or low Rayleigh number, when T = 0.5, the total entropy generation is the minimum.

关键词： natural convection SiO2-water nanofluid Rayleigh number volume fraction entropy generation

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natural convection of nanofluid over vertical plate embedded in porous medium: prescribed surface heat flux

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Applied Mathematics and Mechanics(English Edition) 2013年第6期34卷 669-686页

作者： A. NOGHREHABADI A. BEHSERESHT M. GHALAMBAZ Department of Mechanical Engineering Shahid Chamran University of Ahvaz

The aim of the present paper is to analyze the natural convection heat and mass transfer of nanofluids over a vertical plate embedded in a saturated Darcy porous medium subjected to surface heat and nanoparticle fluxes. To carry out the numerical solution, two steps are performed. The governing partial differential equations are firstly simplified into a set of highly coupled nonlinear ordinary differential equations by appropriate similarity variables, and then numerically solved by the finite difference method. The obtained similarity solution depends on four non-dimensional parameters, i.e., the Brownian motion parameter （Nb）, the buoyancy ratio （Nr）, the thermophoresis parameter （Nt）, and the Lewis number （Le）. The variations of the reduced Nusselt number and the reduced Sherwood number with Nb and Nt for various values of Le and Nr are discussed in detail. Simulation results depict that the increase in Nb, Nt, or Nr decreases the reduced Nusselt number. An increase in the Lewis number increases both of the reduced Nusselt number and the Sherwood number. The results also reveal that the nanoparticle concentration boundary layer thickness is much thinner than those of the thermal and hydrodynamic boundary layers.

关键词： natural convection porous medium nanofluid surface heat flux surfacenanoparticle flux

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natural convection in an H-Shaped Porous EnclosureFilled with a Nanofluid

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Computers, Materials & Continua 2021年第3期66卷 3233-3251页

作者： Zehba A.S.Raizah Abdelraheem M.Aly Department of Mathematics College of ScienceKing Khalid UniversityAbha62529Saudi Arabia Department of Mathematics South Valley UniversityQena83523Egypt

This study simulates natural convection flow resulting from heat partitions in an H-shaped enclosure filled with a nanofluid using an incompressible smoothed particle hydrodynamics(ISPH)*** right area of the H-shaped enclosure is saturated with non-Darcy porous *** center variable partitions of the H-shaped enclosure walls are kept at a high-temperature *** left and right walls of the H-shaped enclosure are positioned at a low temperature Tc and the other walls are *** ISPH method,the source term in pressure Poisson equation(PPE)is *** influences of the controlling parameters on the temperature distributions,the velocity field and average Nusselt number are *** performed simulations proofed that the length of the heated partitions augments the velocity field and temperature distributions in an H-shaped *** number rises the fluid velocity and heat transfer in an H-shaped *** porous layer on the right side of the H-shaped enclosure at a lower Darcy parameter causes a high resistance force for the fluid flow and heat transfer characteristic inside an H-shaped *** nanoparticles reduces the velocity field and enhances the heat transfer inside an H-shaped enclosure.

关键词： H-shaped enclosure ISPH natural convection nanofluid porous medium

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