M.A. Mansour, Sameh Elsayed Ahmed and Ali J. Chamkha
This paper aims to investigate the entropy generation due to magnetohydrodynamic natural convection flow and heat transfer in a porous enclosure filled with Cu-water nanofluid in…
Abstract
Purpose
This paper aims to investigate the entropy generation due to magnetohydrodynamic natural convection flow and heat transfer in a porous enclosure filled with Cu-water nanofluid in the presence of viscous dissipation effect. The left and right walls of the cavity are thermally insulated. There are heated and cold parts, and these are placed on the bottom and top wall, respectively, whereas the remaining parts are thermally insulated.
Design/methodology/approach
The finite volume method is used to solve the dimensionless partial differential equations governing the problem. A comparison with previously published woks is presented and is found to be in an excellent agreement.
Findings
The minimization of entropy generation and local heat transfer according to different values of the governing parameters are presented in details. It is found that the presence of magnetic field has negative effects on the local entropy generation because of heat transfer and the local total entropy generation. Also, the increase in the heated part length leads to a decrease in the local Nusselt number.
Originality/value
This problem is original, as it has not been considered previously.
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Abdelraheem M. Aly, Sameh Elsayed Ahmed and Zehba Raizah
The purpose of this paper is to study the unsteady ferrofluid flow with a hot source helix inside a cavity under the impacts of a variable magnetic field by using the…
Abstract
Purpose
The purpose of this paper is to study the unsteady ferrofluid flow with a hot source helix inside a cavity under the impacts of a variable magnetic field by using the incompressible smoothed particle hydrodynamics method.
Design/methodology/approach
The governing equations are formulated by considering the basics of the magnetohydrodynamic and ferrohydrodynamics. Different locations of a variable magnetic source outside the geometry are investigated. The helical coils are extensively applied in the cooling and heating of air conditioners and heat pumps. Computations were carried out for different lengths of the heated helix (0.2 ≤ Lh ≤ 0.8), different locations of the magnetic source, (a = 0.5, b = −0.01), (a = 0.5, b = 1.01), (a = 1.01, b = 0.5), (a = −0.01, b = 0.5), different numbers of the inner helix (one helix, two helixes and three helixes) and different values of the nanoparticles volume fraction (0% ≤ ϕ ≤ 10%).
Findings
The outcomes of the investigations revealed that an increase in the lengths of a helix by 0.4 results in a reduction of the stream function by 25.60%. In addition, when the magnetic wire is located near the center of the right wall, the maximum values of the average Nusselt number are obtained while the smallest values of the average Nusselt number are given when the magnetic source is located near center of the top wall.
Originality/value
The novelty of this paper is investigating the natural convection flow from two different models of an inner hot helix inside a cavity with considering different locations of variable magnetic sources.
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The Galerkin finite element method (FEM) based on the characteristic-based split (CBS) scheme is applied to simulate the nanofluid flow and thermal fields inside an inclined…
Abstract
Purpose
The Galerkin finite element method (FEM) based on the characteristic-based split (CBS) scheme is applied to simulate the nanofluid flow and thermal fields inside an inclined geometry filled by a heat-generating hydrodynamically and thermally anisotropic non-Darcy porous medium using the local thermal non-equilibrium model (LTNEM). Property of the hydrodynamic anisotropy is taken in both the Forchheimer coefficient and permeability and these tools are considered as functions of inclination of the principal axes. Also, the thermal conductivity for the porous phase is assumed to be anisotropic.
Design/methodology/approach
The Galerkin FEM based on the CBS scheme is applied to solve the partial differential equations governing the flow and thermal fields.
Findings
It is noted that the net rate of the heat transfer between the nanofluid and solid phases are influenced by variations of the anisotropic properties. Also, the system is reached to the thermal equilibrium state at H > 100. Further, the maximum nanofluid temperature is reduced by 12.27% when the nanoparticles volume fraction is varied from 0% to 4%.
Originality/value
This paper aims to study the nanofluid flow and heat transfer characteristics inside an inclined enclosure filled with a heat-generating, hydrodynamically and thermally anisotropic porous medium using the CBS scheme. The LTNEM is considered between the nanofluid and porous phases while the local thermal equilibrium model (LTEM) between the base fluid (water) and the nanoparticles (alumina) is taken into account. The Galerkin FEM is introduced to discretize the governing system of equations. Also, examine influences of the anisotropic properties (permeability, Forchheimer terms and thermal conductivity of the porous medium), inclination angle and nanoparticles volume fraction on the net rate of the heat transfer between the nanofluid and porous phases and on the local thermal non-equilibrium state is one of the concerns of this paper.
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A.M. Rashad, Sameh Elsayed Ahmed and Mohamed Ahmed Mansour
The purpose of this numerical paper is to investigate the simulation of an unsteady double diffusive natural convection in square enclosure filled with a porous medium with…
Abstract
Purpose
The purpose of this numerical paper is to investigate the simulation of an unsteady double diffusive natural convection in square enclosure filled with a porous medium with various boundary conditions in the presence of thermal radiation and chemical reaction effects.
Design/methodology/approach
In this study, the governing dimensionless equations were written using the Brinkman Forchheimer extended Darcy model. They are numerically solved by using finite difference method by applying adiabatic boundary condition in top surface. The bottom surface is maintained at uniform temperature and concentration and left and right vertical walls are cooled.
Findings
Results are presented by streamlines, isotherms, temperature and concentration contours profiles as well as the local Nusselt number and Sherwood numbers for different values of the governing parameters such as Darcy number, buoyancy ratio, Rayleigh number, thermal radiation parameter and chemical reaction parameter. It is found that that both of the local Nusselt and Sherwood numbers increase as the Rayleigh number, buoyancy ratio and Darcy number increase. Moreover, increasing the thermal radiation effects leads to a pronounced increase in the local Nusselt number, while the opposite behavior is displayed by the local Sherwood number. Furthermore, the local Sherwood number increases and the local Nusselt number decrease when the chemical reaction parameter increase.
Originality/value
The originality of this study is the square cavity with various boundary conditions filled with a porous medium with thermal radiation and chemical reaction effects.