Convective Heat Transfer Utilizing Magnetic Nanoparticles in the Presence of a Sloping Magnetic Field Inside a Square Enclosure

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Latifa M. Al-Balushi ◽  
M. M. Rahman
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Magnetic Nanoparticles ◽  
Shear Rate ◽  
Average Nusselt Number ◽  
Hartmann Number ◽  
The Other ◽  
Square Enclosure ◽  
Thermal Boundary Conditions

Unsteady natural convection flow and heat transfer utilizing magnetic nanoparticles in the presence of a sloping magnetic field inside a square enclosure are simulated numerically following nonhomogeneous dynamic model. Four different thermal boundary conditions: constant, parabolic in space, sinusoidally in space, and time for the bottom hot wall are considered. The top wall of the enclosure is cold while the vertical walls are thermally insulated. Galerkin weighted residual finite element method is used to solve the governing nondimensional partial differential equations. For simulations, 12 types of nanofluids consisting magnetite (Fe3O4), cobalt ferrite (CoFe2O4), Mn–Zn ferrite (Mn–ZnFe2O4), and silicon dioxide (SiO2) nanoparticles along with water, engine oil, and kerosene as base fluids are used. The effects of the important model parameters such as Hartmann number, magnetic field sloping angle, and thermal Rayleigh number on the flow fields are investigated. The results show that the average Nusselt number, shear rate, as well as the nanofluid velocity decreases as the Hartmann number intensifies. Moreover, the rate of heat transfer in nanofluid exaggerates with the increase of the thermal Rayleigh number and the magnetic field sloping angle. Sinusoidally varied in space thermal boundary condition at the bottom wall provides the highest average Nusselt number and the shear rate compared to the other types of thermal boundary conditions studied here. For this case, the highest average Nusselt number is obtained for the Mn–ZnFe2O4–Ke nanofluid. On the other hand, Fe3O4–H2O nanofluid delivers the highest shear rate compared to the other premeditated nanofluids.

Influence of Partition Length on Natural Convection in Partially Divided Square Enclosure

2007 ◽  
Vol 129 (11) ◽  
pp. 1592-1599 ◽  
Author(s):  
C. D. Sankhavara ◽  
H. J. Shukla
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Square Enclosure ◽  
Thermal Boundary Conditions ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Good Agreement

Numerical investigation is carried out for natural convection in square enclosures consisting of partitions protruding from the end walls with different thermal boundary conditions at the end walls and partitions. The vertical walls were maintained isothermal at different temperatures. The Rayleigh number varies from 104 to 106 and the Prandtl number is 0.71. The thickness of the partition is fixed and is equal to one-tenth of the width of the enclosure. Their nondimensional length (l∕H) varies from 0 (a nonpartitioned enclosure) to 0.5 (two separate enclosures). A good agreement was found between the results in the present study and those published previously. The partitions were found to significantly influence the convective heat transfer. The average Nusselt number is less in the presence of partitions, and it decreases with increasing partition length (l∕H) from 0 to 0.5.

Effect of magnetic field-dependent thermal conductivity on natural convection of magnetic nanofluid inside a square enclosure

2019 ◽  
Vol 29 (4) ◽  
pp. 1466-1489 ◽  
Author(s):  
Mohammadhossein Hajiyan ◽  
Shohel Mahmud ◽  
Mohammad Biglarbegian ◽  
Hussein A. Abdullah ◽  
A. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Magnetic Nanofluid ◽  
Content Type ◽  
Square Enclosure ◽  
Field Dependent

Purpose The purpose of this paper is to investigate the convective heat transfer of magnetic nanofluid (MNF) inside a square enclosure under uniform magnetic fields considering nonlinearity of magnetic field-dependent thermal conductivity. Design/methodology/approach The properties of the MNF (Fe3O4+kerosene) were described by polynomial functions of magnetic field-dependent thermal conductivity. The effect of the transverse magnetic field (0 < H < 105), Hartmann Number (0 < Ha < 60), Rayleigh number (10 <Ra <105) and the solid volume fraction (0 < φ < 4.7%) on the heat transfer performance inside the enclosed space was examined. Continuity, momentum and energy equations were solved using the finite element method. Findings The results show that the Nusselt number increases when the Rayleigh number increases. In contrast, the convective heat transfer rate decreases when the Hartmann number increases due to the strong magnetic field which suppresses the buoyancy force. Also, a significant improvement in the heat transfer rate is observed when the magnetic field is applied and φ = 4.7% (I = 11.90%, I = 16.73%, I = 10.07% and I = 12.70%). Research limitations/implications The present numerical study was carried out for a steady, laminar and two-dimensional flow inside the square enclosure. Also, properties of the MNF are assumed to be constant (except thermal conductivity) under magnetic field. Practical implications The results can be used in thermal storage and cooling of electronic devices such as lithium-ion batteries during charging and discharging processes. Originality/value The accuracy of results and heat transfer enhancement having magnetic field-field-dependent thermal conductivity are noticeable. The results can be used for different applications to improve the heat transfer rate and enhance the efficiency of a system.

scholarly journals Natural convection in a differentially heated enclosure with triangular roof

1970 ◽  
Vol 39 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sumon Saha ◽  
Noman Hasan ◽  
Chowdhury Md Feroz
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Natural Convection ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Element Analysis ◽  
Left Wall ◽  
Square Enclosure

A numerical study has been carried out for laminar natural convection heat transfer within a two-dimensional modified square enclosure having a triangular roof. The vertical sidewalls are differentially heated considering a constant flux heat source strip is flush mounted with the left wall. The opposite wall is considered isothermal having a temperature of the surrounding fluid. The rest of the walls are adiabatic. Air is considered as the fluid inside the enclosure. The solution has been carried out on the basis of finite element analysis by a non-linear parametric solver to examine the heat transfer and fluid flow characteristics. Different heights of the triangular roof have been considered for the present analysis. Fluid flow fields and isotherm patterns and the average Nusselt number are presented for the Rayleigh numbers ranging from 103 to 106 in order to show the effects of these governing parameters. The average Nusselt number computed for the case of isoflux heating is also compared with the case of isothermal heating as available in the literature. The outcome of the present investigation shows that the convective phenomenon is greatly influenced by the inclined roof height. Keywords: Natural convection, triangular roof, Rayleigh number, isoflux heating. Doi:10.3329/jme.v39i1.1826 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 1-7

Numerical Thermal Analysis of a Hot Non-circular Rotating Cylinder in the Presence of a Magnetic Field

2021 ◽  
Author(s):  
Hojjat Khozeymeh-Nezhad ◽  
Yaser Basati ◽  
Hamid Niazmand
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Transfer Rate ◽  
Elliptic Cylinder ◽  
Optimal Location ◽  
Elliptical Cylinder ◽  
Square Enclosure ◽  
Cylinder Rotation

Abstract In the present paper for the first time, a Lattice Boltzmann Simulation is performed to analyze the simultaneous effects of a hot rotating elliptic cylinder and the magnetic field on the mixed convection flow in a square enclosure. Complicated flow patterns and isotherms plots are found and analyzed in the concentric annulus between the internal elliptic cylinder and the outer square enclosure. Results indicate that increasing the Reynolds number, instantaneous averaged Nusselt number of the enclosure and its oscillation amplitude increase, while decrease with increasing the Hartmann number especially at its lower values. Furthermore, response surface method is adopted to find the optimal location of the elliptic cylinder. Response surface optimization results reveal that the average Nusselt number shows a decreasing-increasing trend with increasing both non-dimensional parameters of cylinder center (Xc,Yc) Finally, the optimal location of the elliptic cylinder for the maximum heat transfer rate is obtained as Xc=0.65 and Yc=0.35. Moreover, a comparative study is performed to evaluate the heat transfer effects of the elliptical cylinder rotation as compared to circular cylinder. It was found that the elliptical cylinder rotation has a significant effect on the heat transfer enhancement, especially at high values of Re and Ha. As an example, the heat transfer rate for the elliptical cylinder at Re=200 is increased by 13 % and 34% as compared to the circular cylinder at Ha=50 and 100, respectively.

scholarly journals Effects of a Rotating Cone on the Mixed Convection in a Double Lid-Driven 3D Porous Trapezoidal Nanofluid Filled Cavity under the Impact of Magnetic Field

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 449 ◽  
Author(s):  
Ali J. Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Rotational Velocity ◽  
Rotating Cone ◽  
The Impact

Effects of a rotating cone in 3D mixed convection of CNT-water nanofluid in a double lid-driven porous trapezoidal cavity is numerically studied considering magnetic field effects. The numerical simulations are performed by using the finite element method. Impacts of Richardson number (between 0.05 and 50), angular rotational velocity of the cone (between −300 and 300), Hartmann number (between 0 and 50), Darcy number (between 10 − 4 and 5 × 10 − 2 ), aspect ratio of the cone (between 0.25 and 2.5), horizontal location of the cone (between 0.35 H and 0.65 H) and solid particle volume fraction (between 0 and 0.004) on the convective heat transfer performance was studied. It was observed that the average Nusselt number rises with higher Richardson numbers for stationary cone while the effect is reverse for when the cone is rotating in clockwise direction at the highest supped. Higher discrepancies between the average Nusselt number is obtained for 2D cylinder and 3D cylinder configuration which is 28.5% at the highest rotational speed. Even though there are very slight variations between the average Nu values for 3D cylinder and 3D cone case, there are significant variations in the local variation of the average Nusselt number. Higher enhancements in the average Nusselt number are achieved with CNT particles even though the magnetic field reduced the convection and the value is 84.3% at the highest strength of magnetic field. Increasing the permeability resulted in higher local and average heat transfer rates for the 3D porous cavity. In this study, the aspect ratio of the cone was found to be an excellent tool for heat transfer enhancement while 95% enhancements in the average Nusselt number were obtained. The horizontal location of the cone was found to have slight effects on the Nusselt number variations.

Investigation of heat transfer of MHD Al2O3/water nanofluid in an enclosure with a semicircular wall and a heating obstacle

2019 ◽  
Vol 30 (12) ◽  
pp. 1950105 ◽  
Author(s):  
Yuan Ma ◽  
Zhigang Yang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Flow Pattern ◽  
Average Nusselt Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Nanoparticle Volume Fraction ◽  
Number Formula

Lattice Boltzmann method (LBM) was used to simulate two-dimensional MHD Al2O3/water nanofluid flow and heat transfer in an enclosure with a semicircular wall and a triangular heating obstacle. The effects of nanoparticle volume fraction ([Formula: see text]), Rayleigh number [Formula: see text], Hartmann number [Formula: see text] and heating obstacle position (Cases 1–7) on flow pattern, temperature distribution and rate of heat transfer were investigated. The results show that with the enhancing Rayleigh number, the increasing nanoparticle volume fraction and the reducing Hartmann number, an enhancement in the average Nusselt number and the heat transfer appeared. The effect of Ha on the average Nu increases by increasing the Ra. It can also be found that the action of changing the heating obstacle position on the convection heat transfer is more important than that on the conduction heat transfer. The higher obstacle position in Cases 6 and 7 leads to the small value of the average Nusselt number. Moreover, the effect of Ha on average Nu in Case 1 at [Formula: see text] is more significant than other cases because the flow pattern in Case 1 is changed as increasing Ha.

scholarly journals CONVECTIVE HEAT TRANSFER ON STENOSED BLOOD FLOW THROUGH PERMEABLE MICROCIRCULATION IN THE PRESENCE OF A MAGNETIC FIELD

2020 ◽  
Author(s):  
Alana Sankar ◽  
Sreedhara Rao Gunakala ◽  
Donna Comissiong
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Blood Flow ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Hartmann Number ◽  
Darcy Number ◽  
Flow Through

Blood flow through permeable microcirculation in the presence of a composite stenosis, an external magnetic field and convective heat transfer was examined. A two-layered model for the blood consisting of a fluid-particle suspension in the core region with a peripheral cell-free plasma layer was used. The proposed system of equations was solved and plots were generated. In the presence of permeable walls, an external magnetic field and convective heat transfer, the temperature of the blood, friction-factor Reynolds number and Nusselt number were investigated. The temperature of the blood increased when the Hartmann number increased, Darcy number increased, haematocrit level increased or the peripheral layer thinned. The friction-factor Reynolds number product increased as the haematocrit, Hartmann number, stenosis height or Darcy number increased. The Nusselt number decreased as the Hartmann number, haematocrit, stenosis height or Darcy number increased. These results were interpreted in terms of the physical situation. This study aids in understanding the effects of wall permeability, a magnetic field and the presence of heat transfer on different diseased arterial systems in the future.

Numerical Study of Magnetic Field Effects on Buoyancy Driven Convection in a Non-Isothermally Heated Square Enclosure

2011 ◽  
Vol 312-315 ◽  
pp. 536-541
Author(s):  
Ghanbar Ali Sheikhzadeh ◽  
Mohsen Pirmohammadi ◽  
A. Fattahi ◽  
M.A. Mehrabian
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Hartmann Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Magnetic Field Effects ◽  
Left Wall ◽  
Square Enclosure ◽  
The Right ◽  
Sinusoidal Function

Numerical simulation of natural convection heat transfer in the presence of a magnetic field is analyzed in a non-isothermally heated square enclosure. The left wall is heated and cooled with a sinusoidal heat source and the right wall is cooled isothermally. The horizontal walls of the enclosure are adiabatic. The effects of Rayleigh number (Ra = 104, 105 and 106), Hartmann number (Ha = 0, 25, 50 and 100) and amplitude of sinusoidal function (n = 0.25, 0.5 and 1) on temperature and flow fields are analyzed. It is observed that the rate of heat transfer is decreased with increasing the Hartmann number; it is also decreased when decreasing the amplitude of sinusoidal function.

scholarly journals Pulsating Flow of CNT–Water Nanofluid Mixed Convection in a Vented Trapezoidal Cavity with an Inner Conductive T-Shaped Object and Magnetic Field Effects

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 848 ◽  
Author(s):  
Ali J. Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Steady Flow ◽  
Average Nusselt Number ◽  
Pulsating Flow ◽  
Cavity Wall ◽  
Magnetic Field Effects ◽  
Field Effects

Mixed convection of carbon-nanotube/water nanofluid in a vented cavity with an inner conductive T-shaped object was examined under pulsating flow conditions under magnetic field effects with finite element method. Effects of different parameters such as Richardson number (between 0.05 and 50), Hartmann number (between 0 and 30), cavity wall inclination (between 0 ∘ and 10 ∘ ), size (between 0.1 H and 0.4 H) and orientation (between −90 ∘ and 90 ∘ ) of the T-shaped object, and amplitude (between 0.5 and 0.9) and frequency (Strouhal number between 0.25 and 5) of pulsating flow on the convective flow features were studied. It was observed that the average Nusselt number enhanced with the rise of strength of magnetic field, solid nanoparticle volume fraction, and amplitude of the pulsation, while the effect was opposite for higher values of Ri number and cavity wall inclination angle. The presence of the T-shaped object and adjusting its size and orientation had significant impact on the main flow stream from inlet to outlet and recirculations around the T-shaped object and in the vicinity of hot wall of the cavity along with the magnetic field strength. Pulsating flow resulted in heat transfer enhancement as compared to steady flow case for all configurations. However, the amount of increment was different depending on the variation of the parameters of interest. Heat transfer enhancements were 41.85% and 20.81% when the size of the T-shaped object was increased from 0.1 H to 0.4 H. The T-shaped object can be utilized in the vented cavity as an excellent tool for convective heat transfer control. As highly conductive CNT particles were used in water, significant enhancements in the average Nusselt number between 97% and 108% were obtained both in steady flow and in pulsating flow cases when magnetic field was absent or present.

Magnetic field impact on nanofluid convective flow in a vented trapezoidal cavity using Buongiorno's mathematical model

2019 ◽  
Vol 88 (1) ◽  
pp. 11101 ◽  
Author(s):  
Mahdi Benzema ◽  
Youb Khaled Benkahla ◽  
Ahlem Boudiaf ◽  
Sief-Eddine Ouyahia ◽  
Mohammed El Ganaoui
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Behavior ◽  
Brownian Diffusion ◽  
High Concentration ◽  
Wide Range

Numerical study for the effect of an external magnetic field on the mixed convection of Al2O3–water Newtonian nanofluid in a right-angle vented trapezoidal cavity was performed using the finite volume method. The non-homogeneous Buongiorno model is applied for numerical description of the dynamic phenomena inside the cavity. The nanofluid, with low temperature and high concentration, enters the cavity through the upper open border, and is evacuated through opening placed at the right end of the bottom wall. The cavity is heated from the inclined wall, while the remainder walls are adiabatic and impermeable to both the base fluid and nanoparticles. After validation of the model, the analysis was carried out for a wide range of Hartmann number (0 ≼ Ha ≼ 100) and nanoparticles volume fraction (0 ≼ ϕ0 ≼ 0.06). The flow behavior as well as the temperature and nanoparticles distribution shows a particular sensitivity to the variations of both the Hartmann number and the nanofluid concentration. The domination of conduction mechanism at high Hartmann numbers reflects the significant effect of Brownian diffusion which tends to uniform the distribution of nanoparticles in the domain. The average Nusselt number which increases with the nanoparticles addition, depends strongly on the Hartmann number. Finally, a correlation predicting the average Nusselt number within such geometry as a function of the considered parameters is proposed.

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