The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid

2019 ◽  
Vol 29 (10) ◽  
pp. 3685-3706
Author(s):  
Zafar Namazian ◽  
S.A.M. Mehryan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Content Type ◽  
Viscosity Parameter ◽  
Micropolar Nanofluid ◽  
Free Convection Heat

Purpose The purpose of this study is to numerically study the heat transfer of free convection of a magnetizable micropolar nanofluid inside a semicircular enclosure. Design/methodology/approach The flow domain is under simultaneous influences of two non-uniform magnetic fields generated by current carrying wires. The directions of the currents are the same. Although the geometry is symmetric, it is physically asymmetric. The impacts of key parameters, including Rayleigh number Ra = 103-106, Hartman number Ha = 0-50, vortex viscosity parameter Δ = 0-4, nanoparticles volume fraction φ = 0-0.04 and magnetic number Mnf = 0-1000, on the macro- and micro-scales flows, temperature and heat transfer rate are studied. Finding The outcomes show that dispersing of the nanoparticles in the host fluid increases the strength of macro- and micro-scale flows. When Mnf = 0, the increment of the vortex viscosity parameter increases the strength of the particles micro-rotations, while this characteristic is decreased by growing Δ for Mnf ≠ 0. The increment of Δ and Ha decreases the rate of heat transfer. The increment of Ha decreases the enhancement percentage of heat transfer rate because of dispersing nanoparticles, known as En parameter. In addition, the value of Δ has no effect on En. Moreover, the average Nusselt number Nuavg and En remain constant by increasing the magnetic number Mnf for different volume fraction values. Originality/value The authors believe that all of the results, both numerical and asymptotic, are original and have not been published elsewhere yet.

Effects of Corona Discharge on Free-Convection Heat Transfer Inside a Vertical Hollow Cylinder

1984 ◽  
Vol 106 (2) ◽  
pp. 346-351 ◽  
Author(s):  
M. E. Franke ◽  
K. E. Hutson
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Corona Discharge ◽  
Heat Transfer Rate ◽  
Hollow Cylinder ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Inside Surface ◽  
Convection Heat ◽  
Free Convection Heat

Vortex rolls induced inside a vertical hollow cylinder are found to increase the free-convection heat transfer rate from the inside surface. The vortex rolls are induced by the corona wind generated between 0.05-mm-dia wire electrodes placed vertically on the inside surface of the vertical hollow cylinder. The increase in heat transfer rate is determined experimentally and is based on the heat input required to maintain the inside surface of the cylinder at constant temperature. The experimental results without corona discharge are compared with an analytical heat balance. A Mach-Zehnder interferometer is used for boundary layer visualization.

Numerical analysis of mixed convection of different nanofluids in concentric annulus

2019 ◽  
Vol 29 (4) ◽  
pp. 1506-1525 ◽  
Author(s):  
Ahad Abedini ◽  
Saeed Emadoddin ◽  
Taher Armaghani
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Flow Pattern ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Simple Algorithm ◽  
Content Type ◽  
Volume Method

Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

Manninen’s mixture model for conjugate conduction and mixed convection heat transfer of a nanofluid in a rotational/stationary circular enclosure

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faraz Hoseininejad ◽  
Saeed Dinarvand ◽  
Mohammad Eftekhari Yazdi
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Content Type ◽  
Mixed Convection Heat Transfer ◽  
Conjugate Conduction

Purpose This study aims to investigate numerically the problem of conjugate conduction and mixed convection heat transfer of a nanofluid in a rotational/stationary circular enclosure using a two-phase mixture model. Design/methodology/approach Hot and cold surfaces on the wall or inside the enclosure (heater and cooler) are maintained at constant temperature of Th and Tc, respectively, whereas other parts are thermally insulated. To examine the effects of various parameters such as Richardson number (0.01 = Ri =100), thermal conductivity ratio of solid to base fluid (1 = Kr = 100), volume fraction of nanoparticle (0 = φ = 0.05), insertion of conductive covers (C.Cs) around the heater in a different shape (triangular, circular or square), segmentation and arrangement of the conductive blocks (C.Bs) and rotation direction of the enclosure on the flow structure and heat transfer rate, two-dimensional equations of mass, momentum and energy conservation, as well as volume fraction, are solved using finite volume method and Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm. Findings The results show that inserting C.C around heater can increase or decrease heat transfer rate, and it depends on thermal conductivity ratio of solid to pure fluid. Also, it is found that by the division of C.B and location of its portions in a horizontal configuration, heat transfer rate reduces. Moreover, it is observed that external heating and cooling of the enclosure causes enhancement of heat transfer relative to that of internal heating and cooling. Finally, results illustrate that under the condition that cylinders rotate in the same direction, the heat transfer rate increases as compared to those that rotate in the opposite direction. Hence rotation direction of cylinders can be used as a desired parameter for controlling heat transfer rate. Originality/value A comprehensive report of results for the problem of conjugate conduction and mixed convection heat transfer in a circular cylinder containing different shapes of C.C, conducting obstacle and heater and cooler has been presented. An efficient numerical technique has been developed to solve this problem. The achievements of this paper are purely original, and the numerical results were never published by any researcher.

3D optimization of baffle arrangement in a multi-phase nanofluid natural convection based on numerical simulation

2019 ◽  
Vol 30 (5) ◽  
pp. 2583-2605 ◽  
Author(s):  
Mohammad Mohsen Peiravi ◽  
Javad Alinejad ◽  
D.D. Ganji ◽  
Soroush Maddah
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Target Function ◽  
Optimal Arrangement ◽  
Content Type ◽  
Multi Phase

Purpose The purpose of this study is investigating the effect of using multi-phase nanofluids, Rayleigh number and baffle arrangement simultaneously on the heat transfer rate and Predict the optimal arrangement type of baffles in the differentiation of Rayleigh number in a 3D enclosure. Design/methodology/approach Simulations were performed on the base of the L25 Taguchi orthogonal array, and each test was conducted under different height and baffle arrangement. The multi-phase thermal lattice Boltzmann based on the D3Q19 method was used for modeling fluid flow and temperature fields. Findings Streamlines, isotherms, nanofluid volume fraction distribution and Nusselt number along the wall surface for 104 < Ra < 108 have been demonstrated. Signal-to-noise ratios have been analyzed to predict optimal conditions of maximize and minimize the heat transfer rate. The results show that by choosing the appropriate height and arrangement of the baffles, the average Nusselt number can be changed by more than 57 per cent. Originality/value The value of this paper is surveying three-dimensional and two-phase simulation for nanofluid. Also using the Taguchi method for Predicting the optimal arrangement type of baffles in a multi-part enclosure. Finally statistical analysis of the results by using of two maximum and minimum target Function heat transfer rates.

scholarly journals Numerical Study of Natural Convection Heat Transfer in a Porous Annulus Filled with a Cu-Nanofluid

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 990
Author(s):  
Lingyun Zhang ◽  
Yupeng Hu ◽  
Minghai Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Radius Ratio ◽  
Natural Convection Heat Transfer ◽  
Nanoparticle Volume Fraction ◽  
Convection Heat

Natural convection heat transfer in a porous annulus filled with a Cu nanofluid has been investigated numerically. The Darcy–Brinkman and the energy transport equations are employed to describe the nanofluid motion and the heat transfer in the porous medium. Numerical results including the isotherms, streamlines, and heat transfer rate are obtained under the following parameters: Brownian motion, Rayleigh number (103–105), Darcy number (10−4–10−2), nanoparticle volume fraction (0.01–0.09), nanoparticle diameter (10–90 nm), porosity (0.1–0.9), and radius ratio (1.1–10). Results show that Brownian motion should be considered. The nanoparticle volume fraction has a positive effect on the heat transfer rate, especially with high Rayleigh number and Darcy number, while the nanoparticle diameter has an inverse influence. The heat transfer rate is enhanced with the increase of porosity. The radius ratio has a significant influence on the isotherms, streamlines, and heat transfer rate, and the rate is greatly enhanced with the increase of radius ratio.

3D natural convection on a horizontal and vertical thermally active plate in a closed cubical cavity

2016 ◽  
Vol 26 (8) ◽  
pp. 2528-2542 ◽  
Author(s):  
Abimanyu Purusothaman ◽  
Abderrahmane Baïri ◽  
Nagarajan Nithyadevi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Numerical Code ◽  
Heated Plate ◽  
Algebraic Equations ◽  
Content Type ◽  
Cubical Cavity

Purpose The purpose of this paper is to examine numerically the natural convection heat transfer in a cubical cavity induced by a thermally active plate. Effects of the plate size and its orientation with respect to the gravity vector on the convective heat transfer and the flow structures inside the cavity are studied and highlighted. Design/methodology/approach The numerical code is based on the finite volume method with semi-implicit method for pressure-linked equation algorithm. The convective and diffusive terms in momentum equations are handled by adopting the power law scheme. Finally, the discretized sets of algebraic equations are solved by the line-by-line tri-diagonal matrix algorithm. Findings The results show that plate orientation and size plays a significant role on heat transfer. Also, the heat transfer rate is an increasing function of Rayleigh number for both orientations of the heated plate. Depending on the thermal management of the plate and its application (as in electronics), the heat transfer rate is maximized or minimized by selecting appropriate parameters. Research limitations/implications The flow is assumed to be 3D, time-dependent, laminar and incompressible with negligible viscous dissipation and radiation. The fluid properties are assumed to be constant, except for the density in the buoyancy term that follows the Boussinesq approximation. Originality/value The present work will give some additional knowledge in designing sealed cavities encountered in some engineering applications as in aeronautics, automobile, metallurgy or electronics.

MHD hybrid nanofluid flow with convective heat transfer over a permeable stretching/shrinking surface with radiation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nur Syahirah Wahid ◽  
Norihan Md Arifin ◽  
Najiyah Safwa Khashi'ie ◽  
Ioan Pop ◽  
Norfifah Bachok ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Hybrid Nanofluid ◽  
Convective Boundary Conditions ◽  
Nanofluid Flow ◽  
Convective Boundary ◽  
Content Type ◽  
Shrinking Surface

Purpose The purpose of this paper is to numerically investigate the hybrid nanofluid flow with the imposition of magnetohydrodynamic (MHD) and radiation effects alongside the convective boundary conditions over a permeable stretching/shrinking surface. Design/methodology/approach The mathematical model is formulated in the form of partial differential equations (PDEs) and are then transformed into the form of ordinary differential equations (ODEs) by using the similarity variables. The deriving ODEs are solved numerically by using the bvp4c solver in MATLAB software. Stability analysis also has been performed to determine the stable solution among the dual solutions obtain. For method validation purposes, a comparison of numerical results has been made with the previous studies. Findings The flow and the heat transfer of the fluid at the boundary layer are described through the plot of the velocity profile, temperature profile, skin friction coefficient and local Nusselt number that are presented graphically. Dual solutions are obtained, but only the first solution is stable. For the realizable solution at the shrinking surface, the proliferation of nanoparticle volume fraction (copper) and magnetic (magnetohydrodynamics) parameters can impede the boundary layer separation. Also, Biot number could enhance the temperature profile and the heat transfer rate at the shrinking surface region. The incrementation of 0.1% of Biot number has enhanced the heat transfer rate by approximately 0.1% and the incrementation of 0.5% volume fraction for copper has reduced the heat transfer rate by approximately 0.17%. Originality/value The presented model and numerical results are original and new. It can be used as a future reference for further investigation and related practical application. The main contribution of this investigation includes giving the initial prediction and providing the numerical data for the other researchers for their future reference regarding the impacts of nanoparticles volumetric concentration towards the main physical quantities of interest in the presence of magnetic and radiation parameters with the convective boundary conditions.

Effect of replacing nanofluid instead of water on heat transfer in a channel with extended surfaces under a magnetic field

2019 ◽  
Vol 29 (4) ◽  
pp. 1249-1271 ◽  
Author(s):  
Saeed Aghakhani ◽  
Behzad Ghasemi ◽  
Ahmad Hajatzadeh Pordanjani ◽  
Somchai Wongwises ◽  
Masoud Afrand
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Lower Wall ◽  
Parallel Plates ◽  
Content Type ◽  
Extended Surfaces

PurposeThe purpose of this study is to conduct a numerical analysis of flow and heat transfer of water–aluminum oxide nanofluid in a channel with extended surfaces in the presence of a constant magnetic field. The channel consists of two parallel plates and five obstacles of constant temperature on the lower wall of the channel. The upper wall and the inlet and outlet lengths of the lower wall are insulated. A uniform magnetic field of the magnitude B0 is located beneath the obstacles. The nanofluid enters the channel with a uniform velocity and temperature, and a fully developed flow leaves the channel.Design/methodology/approachThe control volume-based finite difference and the SIMPLE algorithm were used for numerical solution. In addition to examining the effect of the Reynolds number, the effects of Hartman number, the volume fraction of nanoparticles, the height of obstacles, the length of obstacles and the distance between the obstacles were investigated.FindingsAccording to the results, the heat transfer rate increases with an increasing Reynolds number. As the Hartmann number increases, the heat transfer rate increases. The heat transfer rate also increases with an increase in the volume fraction of nanoparticles. The mean Nusselt number is reduced by an increasing height of obstacles. An increase in the distance between the obstacles in the presence of a magnetic field does not have a significant impact on the heat transfer rate. However, the heat transfer rate increases in the absence of a magnetic field, as the distance between the obstacles increases.Originality/valueThis paper is original and unpublished and is not being considered for publication elsewhere.

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