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Numerical Heat Transfer, Part A: Applications
An International Journal of Computation and Methodology
Volume 69, 2016 - Issue 10
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Original articles

Flow and convective heat transfer of a ferro-nanofluid in a double-sided lid-driven cavity with a wavy wall in the presence of a variable magnetic field

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Pages 1186-1200 | Received 10 May 2015, Accepted 01 Jul 2015, Published online: 22 Mar 2016
 

ABSTRACT

In this work, the effect of a variable spatial magnetic field on ferro-nanofluid flow and heat transfer in a double-sided lid-driven enclosure with a sinusoidal hot wall is investigated. The working fluid is a mixture of iron oxide (Fe3O4) nanoparticles and water and is referred to as a ferro-nanofluid. The control volume-based finite element method (CVFEM) is used to solve the governing equations in the stream function–vorticity formulation. In deriving the governing equations for this investigation, the effect of both ferro-hydrodynamics and magneto-hydrodynamics is taken into account. The numerical calculations are performed for different governing parameters namely; the Reynolds number, nanoparticle volume fraction, magnetic number (arising from Ferrohydrodynamics (FHD) consideration), and the Hartmann number (arising from Magnetohydrodynamics (MHD) consideration). The results show that an enhancement in heat transfer has a direct relationship with the Reynolds number and the Hartmann number, but it has an inverse relationship with the magnetic number. Also, it can be concluded that the Nusselt number increases with the increase of the nanoparticle volume fraction, magnetic number, and the Reynolds number while the opposite trend is observed for the Hartmann number.

Nomenclature

a=

dimensionless amplitude of the sinusoidal wall

B=

magnetic induction (= μ0H)

Cp=

specific heat at constant pressure

Ec=

Eckert number

En=

heat transfer enhancement

Hx, Hy=

components of the magnetic field intensity

H=

the magnetic field strength

Ha=

Hartmann number

k=

thermal conductivity

K=

constant parameter

L=

gap between inner and outer boundaries of the enclosure L = rout − rin

MnF=

magnetic number arising from FHD

M=

magnetization

Nu=

Nusselt number

Pr=

Prandtl number (= υf/αf)

Re=

Reynolds number (= ρfL ULid/μf)

T=

fluid temperature

=

Curie temperature

u, v=

velocity components in the x-direction and y-direction

U, V=

dimensionless velocity components in the x-direction and y-direction

x, y=

space coordinates

X, Y=

dimensionless space coordinates

α=

thermal diffusivity

ϕ=

volume fraction

γ=

magnetic field strength at the source

ϵ1=

temperature number (= T1T)

ϵ2=

Curie temperature number

σ=

electrical conductivity

μ=

dynamic viscosity

μ0=

magnetic permeability of vacuum

υ=

kinematic viscosity

=

stream function and dimensionless stream function

Θ=

dimensionless temperature

ρ=

fluid density

ω, Ω=

vorticity and dimensionless vorticity

Subscripts=
c=

cold

h=

hot

ave=

average

loc=

local

nf=

nanofluid

f=

base fluid

s=

solid particles

in=

inner

out=

outer

Nomenclature

a=

dimensionless amplitude of the sinusoidal wall

B=

magnetic induction (= μ0H)

Cp=

specific heat at constant pressure

Ec=

Eckert number

En=

heat transfer enhancement

Hx, Hy=

components of the magnetic field intensity

H=

the magnetic field strength

Ha=

Hartmann number

k=

thermal conductivity

K=

constant parameter

L=

gap between inner and outer boundaries of the enclosure L = rout − rin

MnF=

magnetic number arising from FHD

M=

magnetization

Nu=

Nusselt number

Pr=

Prandtl number (= υf/αf)

Re=

Reynolds number (= ρfL ULid/μf)

T=

fluid temperature

=

Curie temperature

u, v=

velocity components in the x-direction and y-direction

U, V=

dimensionless velocity components in the x-direction and y-direction

x, y=

space coordinates

X, Y=

dimensionless space coordinates

α=

thermal diffusivity

ϕ=

volume fraction

γ=

magnetic field strength at the source

ϵ1=

temperature number (= T1T)

ϵ2=

Curie temperature number

σ=

electrical conductivity

μ=

dynamic viscosity

μ0=

magnetic permeability of vacuum

υ=

kinematic viscosity

=

stream function and dimensionless stream function

Θ=

dimensionless temperature

ρ=

fluid density

ω, Ω=

vorticity and dimensionless vorticity

Subscripts=
c=

cold

h=

hot

ave=

average

loc=

local

nf=

nanofluid

f=

base fluid

s=

solid particles

in=

inner

out=

outer

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