scholarly journals A revised model of "Steady laminar natural convection of nanofluid under the impact of magnetic field on 2-D cavity with radiation" [AIP advances 9, 065008 (2019); https://doi.org/10.1063/1.5109192]

2020 ◽  
Vol 24 (1 Part A) ◽  
pp. 421-425
Author(s):  
Hossam Nabwey
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Natural Convection ◽  
Darcy Number ◽  
Porous Media Flow ◽  
Governing Equations ◽  
Laminar Natural Convection ◽  
The Impact ◽  
Published Paper ◽  
Steady Laminar

This discussion exhibits the major scientific errors on the recent published paper, entitled "Steady Laminar Natural Convection of Nanofluid Under the Impact of Magnetic Field on 2-D Cavity with Radiation" and their corrections indifferently. In Saleem et al. [1], the authors stated in both of abstract and problem assumptions that the non-Darcy model is used for the porous medium, while the porous terms are incompatible with this assumption. In addition, the authors used a non-inclined geometry in their investigation, but the governing equations are conflicting with this hypothesis. Further, the used range of the Darcy number is between 10?2-102 and this range is very large and did not represent the porous media flow. All of these observations make the mathematical formulations and the obtained results of Saleem et al. [1] are wrong. In the following sections, these scientific errors and their corrections will be presented minutely.

scholarly journals Steady laminar natural convection of nanofluid under the impact of magnetic field on two-dimensional cavity with radiation

AIP Advances ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 065008 ◽  
Author(s):  
S. Saleem ◽  
Trung Nguyen-Thoi ◽  
Ahmad Shafee ◽  
Zhixiong Li ◽  
Ebenezer Bonyah ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Natural Convection ◽  
Two Dimensional ◽  
Laminar Natural Convection ◽  
The Impact ◽  
Steady Laminar

scholarly journals Chemical Entropy Generation and MHD Effects on the Unsteady Heat and Fluid Flow through a Porous Medium

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Gamal M. Abdel-Rahman Rashed
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Fluid Flow ◽  
Entropy Generation ◽  
Lewis Number ◽  
Heat Transfer Fluid ◽  
Governing Equations ◽  
Flow Through ◽  
Heat And Fluid Flow ◽  
Chemical Reaction Parameter

Chemical entropy generation and magnetohydrodynamic effects on the unsteady heat and fluid flow through a porous medium have been numerically investigated. The entropy generation due to the use of a magnetic field and porous medium effects on heat transfer, fluid friction, and mass transfer have been analyzed numerically. Using a similarity transformation, the governing equations of continuity, momentum, and energy and concentration equations, of nonlinear system, were reduced to a set of ordinary differential equations and solved numerically. The effects of unsteadiness parameter, magnetic field parameter, porosity parameter, heat generation/absorption parameter, Lewis number, chemical reaction parameter, and Brinkman number parameter on the velocity, the temperature, the concentration, and the entropy generation rates profiles were investigated and the results were presented graphically.

Natural Convection Inside a Bidisperse Porous Medium Enclosure

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Arunn Narasimhan ◽  
B. V. K. Reddy
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Volume Fraction ◽  
Solid Phase ◽  
Darcy Number ◽  
The Core ◽  
Side Walls ◽  
Porous Blocks ◽  
Rayleigh Numbers

Bidisperse porous medium (BDPM) consists of a macroporous medium whose solid phase is replaced with a microporous medium. This study investigates using numerical simulations, steady natural convection inside a square BDPM enclosure made from uniformly spaced, disconnected square porous blocks that form the microporous medium. The side walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The bidispersion effect is generated by varying the number of blocks (N2), macropore volume fraction (ϕE), and internal Darcy number (DaI) for several enclosure Rayleigh numbers (Ra). Their effect on the BDPM heat transfer (Nu) is investigated. When Ra is fixed, the Nu increases with an increase in both DaI and DaE. At low Ra values, Nu is strongly affected by both DaI and ϕE. When N2 is fixed, at high Ra values, the porous blocks in the core region have negligible effect on the Nu. A correlation is proposed to evaluate the heat transfer from the BDPM enclosure, Nu, as a function of Raϕ, DaE, DaI, and N2. It predicts the numerical results of Nu within ±15% and ±9% in two successive ranges of modified Rayleigh number, RaϕDaE.

Elliptic cavity filled with hybrid nanomaterial under consideration of magnetic field

2020 ◽  
Vol 31 (06) ◽  
pp. 2050080 ◽  
Author(s):  
Ahmad Shafee ◽  
Amin Firouzi ◽  
Nguyen Dang Nam ◽  
Houman Babazadeh
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Hybrid Material ◽  
Homogeneous Model ◽  
Governing Equations ◽  
Hybrid Nanomaterial ◽  
Elliptic Cavity ◽  
Favorable Influence ◽  
New Formula ◽  
The Impact

CVFEM usage for modeling of nanomaterial flow style in a permeable elliptical tank including Lorentz effect was scrutinized in the current research. Hybrid material with use of homogeneous model was applied and radiation term has been involved in governing equations. Outputs have been depicted in contours and plots. In addition, a new formula for Nu was reported. Augment of Nu by considering greater permeability can be explained by stronger temperature gradient in cases with higher Da. Nanomaterial flow becomes suppressed with augment of Ha which results in lower Nu. As Ha was augmented from 0 to 20, 18% reduction was reported in Nu. Permeability has favorable influence on nanomaterial flow and the impact of Ha is the opposite of permeability.

scholarly journals Free convection heat transfer of MgO-MWCNTs/EG hybrid nanofluid in a porous complex shaped cavity with MHD and thermal radiation effects

2019 ◽  
Vol 29 (11) ◽  
pp. 4349-4376 ◽  
Author(s):  
Mohammad Ghalambaz ◽  
Mahmoud Sabour ◽  
Ioan Pop ◽  
Dongsheng Wen
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Porous Medium ◽  
Complex Shape ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Convection Heat ◽  
Governing Equations ◽  
Content Type ◽  
Hybrid Nanofluids

Purpose The present study aims to address the flow and heat transfer of MgO-MWCNTs/EG hybrid nanofluid in a complex shape enclosure filled with a porous medium. The enclosure is subject to a uniform inclined magnetic field and radiation effects. The effect of the presence of a variable magnetic field on the natural convection heat transfer of hybrid nanofluids in a complex shape cavity is studied for the first time. The geometry of the cavity is an annular space with an isothermal wavy outer cold wall. Two types of the porous medium, glass ball and aluminum metal foam, are adopted for the porous space. The governing equations for mass, momentum and heat transfer of the hybrid nanofluid are introduced and transformed into non-dimensional form. The actual available thermal conductivity and dynamic viscosity data for the hybrid nanofluid are directly used for thermophysical properties of the hybrid nanofluid. Design/methodology/approach The governing equations for mass, momentum and heat transfer of hybrid nanofluid are introduced and transformed into non-dimensional form. The thermal conductivity and dynamic viscosity of the nanofluid are directly used from the experimental results available in the literature. The finite element method is used to solve the governing equations. Grid check procedure and validations were performed. Findings The effect of Hartmann number, Rayleigh number, Darcy number, the shape of the cavity and the type of porous medium on the thermal performance of the cavity are studied. The outcomes show that using the composite nanoparticles boosts the convective heat transfer. However, the rise of the volume fraction of nanoparticles would reduce the overall enhancement. Considering a convective dominant regime of natural convection flow with Rayleigh number of 107, the maximum enhancement ratio (Nusselt number ratio compared to the pure fluid) for the case of glass ball is about 1.17 and for the case of aluminum metal foam is about 1.15 when the volume fraction of hybrid nanoparticles is minimum as 0.2 per cent. Originality/value The effect of the presence of a variable magnetic field on the natural convection heat transfer of a new type of hybrid nanofluids, MgO-MWCNTs/EG, in a complex shape cavity is studied for the first time. The results of this paper are new and original with many practical applications of hybrid nanofluids in the modern industry.

A nonlinear stability analysis in a double-diffusive magnetized ferrofluid with magnetic-field-dependent viscosity saturating a porous medium

2009 ◽  
Vol 87 (6) ◽  
pp. 659-673 ◽  
Author(s):  
Sunil ◽  
Amit Mahajan
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Nonlinear Stability ◽  
Stability Result ◽  
Darcy Number ◽  
Linear Instability ◽  
Nonlinear Stability Analysis ◽  
Field Dependent ◽  
Magnetized Ferrofluid ◽  
Mfd Viscosity

A rigorous nonlinear stability result is derived by introducing a suitable generalized energy functional for a magnetized ferrofluid layer heated and soluted from below with magnetic-field-dependent (MFD) viscosity saturating a porous medium, in the stress-free boundary case. The mathematical emphasis is on how to control the nonlinear terms caused by the magnetic-body and inertia forces. For ferrofluids, we find that there is possibility of existence of subcritical instabilities, however, it is noted that, in case of a non-ferrofluid, the global nonlinear stability Rayleigh number is exactly the same as that for linear instability. For lower values of magnetic parameters, this coincidence is immediately lost. The effect of the magnetic parameter, M3; solute gradient, Sf; Darcy number, Da; and MFD viscosity parameter, δ; on the subcritical instability region has also been analyzed.

Numerical Investigation of Natural Convection in an Enclosure Filled with Porous Medium Under Magnetic Field

2007 ◽  
Vol 52 (10) ◽  
pp. 959-971 ◽  
Author(s):  
Min Zeng ◽  
Qiu-Wang Wang ◽  
Zi-Peng Huang ◽  
Gang Wang ◽  
Hiroyuki Ozoe
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Natural Convection ◽  
Numerical Investigation
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