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Numerical Study of Heat Transfer in a Differentially Heated Cavity

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Energy and Power Engineering 2023年第12期15卷 500-516页

作者： Amadou Konfe Adrien Sanebaye Alfred Bayala Sié Kam Laboratory of Thermal and Renewable Energies University Joseph Ki-Zerbo Ouagadougou Burkina Faso

Laminar natural convection is studied in a square cavity filled with air whose two vertical sides are subject to a temperature difference, while the other two horizontal sides are adiabatic. The hot and cold wall temperatures are kept constant. We have presented a dynamic and thermal study of pure natural convection for different values of the Rayleigh number. The numerical simulation was carried out for Rayleigh numbers ranging from 102, 103, …, 105 and the Prandtl number is Pr = 0.71. We used the COMSOL Multiphysic 5.1 software, which allows us to simultaneously solve the coupled physical phenomena in a square enclosure containing air under the Boussinesq approximation. For the coupling of natural convection with radiation from radiative surfaces, both horizontal faces are subjected to radiative flux, and the emissivity of the surfaces varies from ε = 0.1 to 0.8. We have seen that a circulation process is involved. The fluid that is subjected to a high temperature near the hot wall rises to the ceiling and the fluid near the cold wall sinks. This movement continues until the fluid reaches thermal equilibrium. In a natural convection-surface radiation coupling, simulation results indicate that radiative exchange decreases as a function of the Rayleigh number. Surface radiation reduces the flow in the cavity.

关键词： natural convection Square Cavity natural convection Radiation Coupling

Impacts of Heat Flux Distribution, Sloping Magnetic Field and Magnetic Nanoparticles on the natural Convective Flow Contained in a Square Cavity

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Fluid Dynamics & Materials Processing 2020年第3期16卷 441-463页

作者： Latifa M.Al-Balushi M.M.Rahman Department of Mathematics College of ScienceSultan Qaboos UniversityMuscatOman

In the present paper,the effect of the heat flux distribution on the natural convective flow inside a square cavity in the presence of a sloping magnetic field and magnetic nanoparticles is explored numerically.The nondimensional governing equations are solved in the framework of a finite element method implemented using the Galerkin approach.The role played by numerous model parameters in influencing the emerging thermal and concentration fields is examined;among them are:the location of the heat source and its lengthH,the magnitude of the thermal Rayleigh number,the nanoparticles shape and volume fraction,and the Hartmann number.It is found that the nanofluid velocity becomes higher when the thermal source length,the nanoparticles volume fraction and/or the thermal Rayleigh number are increased,while it decreases as the Hartmann number Ha grows and the position of the heat source moves toward the center of the lower wall of the cavity.Moreover,the temperature of the nanofluid grows with the extension of the thermal source and decreases slowly when the heat flux position moves toward the center of the lower wall.The outcomes of the research also indicate that the average Nusselt number becomes smaller on increasing Hartmann number Ha and heat source length H^(*).The addition of Fe_(3)O_(4) to engine oil leads to a higher rate of heat transfer with respect to the addition of SiO_(2) particles.Blade-shaped nanoparticles generate the highest value of the Nusselt number compared to all the other considered shapes.

关键词： Nanofluids magnetic nanoparticles heat source natural convection finite element method square enclosure

natural　CONVECTIVE　HEAT　AND　MASS　TRANSFER　BY　THE　COUPLING　OF　TEMPERATURE　CRADIENT　AND　CONCENTRATION　GRADIENT　IN　A　POROUS　MEDIUM

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Journal of Hydrodynamics 1995年第1期7卷 45-49页

作者： Chen BaO-Ming Fang Zhao-hong (Shandong Architectural and Civil Engineering Institute,Jinan 250014, P. R. China)Wang Bu-xuan(Tsinghua University,Beijing 100084, P. R. China) Shandong Architectural and Civil Engineering Inst Jinan China

The coupling of temperature gradient and concentration gradient and it's effects on heat and mass transfer are considered for natural convection in a porous enclosure. By use of the penalty finite element method, the distributions of flow, temperature and concentration fields are numerically simulated in four kinds of boundary condition. The profiles of heat and mass transfer coefficients along with the vertical wall are shown in the peper.

关键词： porous media natural convection heat and mass transfer.

Influence of Hartmann Number on Convective Flow of Maxwell Fluid between Two Hot Parallel Plates through Porous Medium Subject to Arbitrary Shear Stress at the Boundary

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Journal of Applied Mathematics and Physics 2022年第1期10卷 160-171页

作者： Adnan Ahmad Zaib Un Nisa Mudassar Nazar Muhammad Imran Asjad Mushtaq Ahmad Centre for Advanced Studies in Pure and Applied Mathematics Bahauddin Zakariya University Multan Pakistan Department of Mathematics University of Education Lahore Multan Campus Multan Pakistan School of Mathematical Sciences University of Science and Technology of China Hefei China Department of Mathematics University of Management and Technology Lahore Pakistan

natural convection flow of unsteady Maxwell fluid with the effects of constant magnetic force in the course of a porous media is investigated in this research work. Fluid motion between a channel of parallel plates is tempted by time dependent shear stress applied on one plate. The governing partial differential equations of a model under consideration are transformed into ordinary differential equations by Laplace transform method and then solved for temperature and velocity fields. The obtained results for temperature fields are expressed in terms of complementary error function. The influences of involved parameters likes Hartmann number, Grashf number, Prandlt number and porosity parameter, on temperature and velocity profiles are shown graphically. There is no such result regarding Maxwell fluid in the existing literature.

关键词： natural convection Maxwell Fluid Hot Parallel Plates MHD Porous Media Shear Stress

Three-Dimensional Lattice Kinetic Scheme and its Application to Simulate Incompressible Viscous Thermal Flows

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Communications in Computational Physics 2007年第2期2卷 239-254页

作者： Y.Peng C.Shu Y.T.Chew Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260.

In this paper,the three-dimensional lattice kinetic scheme is presented to simulate incompressible viscous thermal flows.As compared with the standard LBM,the present scheme has the following good features.It can save the computer memory since there is no need to store the density distributions.Like the conventional NS solvers,the implementation of boundary conditions is straightforward since the dependent variables are the macroscopic flow parameters.The easy implementation of boundary conditions is a good property for solving three-dimensional flow problems.The present scheme is validated by simulating the three-dimensional natural convection in an air-filled cubical enclosure,which is heated differentially at two vertical side walls.The obtained numerical results compare very well with available data in the literature.

关键词： Lattice kinetic scheme lattice Boltzmann method three-dimensional incompressible flow natural convection thermal flow.

Evaluation on Heat Transferring Performance of Fabric Heat Sink by Finite Element Modeling

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Journal of Donghua University(English Edition) 2016年第4期33卷 619-624页

作者：杨旭东张华帅胡吉永路玉环李毓陵 Engineering Research Center of Technical Textiles Ministry of EducationDonghua University Key Laboratory of Textile Science & Technology Ministry of EducationDonghua University

Considering the limitation in current manufacturing technology of commercial pin fin heat sinks,a new fabric heat sink has been designed. However,it is lack of an understanding of the heat transferring performance of this new kind of heat sink. In this study,the finite element method (FEM) was used to predict the heat transferring performance of fabric heat sink under the condition of natural convection and forced convection, and its heat transferring performance was compared with that of pin fin heat sink. The results showed that in the condition of natural convection the heat transferring performance of pin fin heat sink was better than that of fabric heat sink, and vice versa under the forced convection condition.

关键词： fabric heat sink pin fin heat sink natural convection forced convection heat transferring

THE EXPERIMENTAL STUDY FOR natural CONVECTIVE HEAT AND MASS TRANSFER IN POROUS MEDIA

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Journal of Hydrodynamics 1998年第4期10卷 90-99页

作者： Chen Bao-mingDept. of Thermal and Civil Engineering, Shandong Institute of Architectural and Civil Engineering, Jinan 250014 ,P. R. China

An electrochemical method is employed to study experimentally natural convection driven by combined thermal and solutal buoyant forces in a fluid-saturated porous enclosure. The horizontal temperature and concentration gradients are imposed in such a way that their effects on the flow are either opposing or augmenting. The inside temperature profiles and heat and mass transfer characteristics on the vertical walls are experimentally determined. The effects of dimensionless parameter Ra, Le, N on flow, heat and mass transfer are discussed in details.

关键词： electrochemical experimental study natural convection heat and mass transfer

Direct Observation of Thermoelectric Magnetic convection in Unidirectionally Solidified Al-Cu Alloys

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Journal of Iron and Steel Research(International) 2012年第S1期19卷 34-39页

作者： Hideyuki Yasuda Keisuke Inoue Yudai Minami Tomoya Nagira Masato Yoshiya Kentaro Uesugi Keiji Umetani Department of Adaptive Machine Systems Osaka UniversityOsaka 565-0871Japan Japan Synchrotron Research Institute/SPring-8 Hyogo 679-5198Japan

This study performed the time-resolved and in-situ observation of unidirectional solidification of A1-Cu and Sn-Bi alloys under a static magnetic field up to 0.45 T.Irt the case of Sn-Bi alloy,the static magnetic field reduced the local convection around the primary dendrite arms.No thermoelectric convection was detected.On the other hand,the thermoelectric convection was clearly observed in Al-Cu alloy.The observed convection was consistently explained by the thermoelectric magnetic convection.According to a simplified model,the thermoelectric magnetic convection can be induced if the difference in the thermoelectric power between the solid and the liquid phases is in the order of 1 μV/K and temperature gradient is several K/mm.

关键词： static magnetic field natural convection thermoelectric effect dendrite

Simulation of an Inductive Weld Pool Support for Deep Penetration Laser Beam Welding of Metal Parts

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Journal of Iron and Steel Research(International) 2012年第S1期19卷 114-117页

作者： BACHMANN Marcel AVILOV Vjaceslav GUMENYUK Andrey RETHMEIER Michael BAM Federal Institute for Materials Research and Testing Unter den Eichen 87Berlin 12205Germany

A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.

关键词： electromagnetic weld pool support laser beam welding Lorentz force Marangoni stresses natural convection