International Journal of Heat and Mass Transfer 136 (2019) 146–156
Contents lists available at ScienceDirect
International Journal of Heat and Mass Transfer
journal homepage: www.elsevier.com/locate/ijhmt
Simulation of convection heat transfer of magnetic nanoparticles
including entropy generation using CVFEM
Tawfeeq Abdullah Alkanhal a, M. Sheikholeslami b, A. Arabkoohsar c, Rizwan-ul Haq d, Ahmad Shafee e,
Zhixiong Li f,g,⇑, I. Tlili h
a
Department of Mechatronics and System Engineering, College of Engineering, Majmaah University, Al-Majmaah 11952, Saudi Arabia
Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Islamic Republic of Iran
Department of Energy Technology, Aalborg University, Denmark
d
Department of Electrical Engineering, Bahria University Islamabad Campus, Islamabad, Pakistan
e
Public Authority of Applied Education & Training, College of Technological Studies, Applied Science Department, Shuwaikh, Kuwait
f
School of Engineering, Ocean University of China, Qingdao 266110, China
g
School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
h
Department of Mechanical and Industrial Engineering, College of Engineering, Majmaah University, Al-Majmaah 11952, Saudi Arabia
b
c
a r t i c l e
i n f o
Article history:
Received 16 December 2018
Received in revised form 23 February 2019
Accepted 26 February 2019
Keywords:
Numerical simulation
MHD
Convection
Nanomaterial
Entropy generation
CVFEM
a b s t r a c t
An investigation has been conducted to study Lorentz effect on nanomaterial behavior within a permeable space including innovative numerical technique namely CVFEM. Iron oxide has been mixed with H2O
and porous domain was filled with this nanomaterial. The impacts of the flow and geometric variables on
entropy generation along with the heat transfer have been examined. The simulations have been carried
out with wide ranges of the magnetic force, permeability and Rayleigh numbers. The outcomes indicate
that the Darcy term has inverse relationship with temperature of hot surface. Stronger convection mode
and lower exergy loss appear when buoyancy forces augment. Entropy generation goes up with growth of
Hartmann number.
Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction
Nanomaterials have the proficiency to augment heat efficiency
of carrier liquids. Base liquid have poor heat transport competence
and should be modified. Various shape and type of nanoparticles
can change the heat transfer rate. Nanomaterials have wide utilization in industrial and technological processes like power generator,
cooling of papers, micro-reactors, etc. Xu et al. [1] developed their
code for nanomaterial flow inside a duct. They considered microorganisms’ impact, too. Hybrid nanoparticles convection within an
annulus with two wires has been simulated by Sheikholeslami
et al. [2]. They employed COMSOL software. Triangular open cavity
has been investigated by Bondareva et al. [3] to find the impact of
Brownian diffusion. Roles of MHD on double diffusion micropolar
flow were analyzed by Mishra et al. [4]. Utilization of CVFEM for
second law analysis has been examined by Sheikholeslami [5].
⇑ Corresponding author at: School of Engineering, Ocean University of China,
Qingdao 266110, China.
E-mail address: zhixiongli@cumt.edu.cn (Z. Li).
https://doi.org/10.1016/j.ijheatmasstransfer.2019.02.095
0017-9310/Ó 2019 Elsevier Ltd. All rights reserved.
He assumed that domain is under the impact of magnetic forces.
Nanomaterial entropy generation due to MHD with including variable heating was modeled by Malik and Nayak [6]. They also utilized porous medium to augment convection. Khan et al. [7] tried
to present Dual solution for unsteady nanomaterial MHD flow.
Enclosure with different permeable block was investigated by
Gibanov et al. [8]. They employed MHD and examined entropy
generation. Rayleigh-Bénard problem with nanomaterial has been
solved by Yadav et al. [9]. They added magnetic force to eliminate
thermal plume. Astanina et al. [10] carried out numerical examination for MHD effect on entropy generation. Qi et al. [11] extended
their LBM code for two phase simulation of nanomaterial with
buoyancy effect. CNT nanoparticles behavior in appearance of
tilted magnetic field was demonstrated by Haq et al. [12]. They utilized two various carrier fluids along slip plate. These days, scientists try to discover new ways to augment thermal properties of
carrier fluid [13–36].
This article aims to study impacts of permeability, buoyancy
and Lorentz forces on the hydrothermal efficiency and entropy
generation of nanomaterial inside a porous tank. Homogeneous
147
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Nomenclature
Ha
Xd
V
B
Da
Nu
T
Be
Ra
Sgen
CVFEM
Hartmann number
exergy loss
vertical velocity
magnetic field
Darcy number
Nusselt number
temperature
Bejan number
Rayleigh number
entropy generation
control volume based finite element method
Greek symbols
dynamic viscosity
b
thermal expansion coefficient
h
temperature
X
vorticity
r
electrical conductivity
l
Subscripts
f
carrier fluid
M
due to Lorenz
th
thermal
nf
nanomaterial
nanomaterial in appearance of magnetic force was simulated via
CVFEM. Various cases have been reported. Based on the outcomes,
good correlations in terms of permeability, buoyancy and Lorentz
forces have been developed.
2. Explanation of geometry and formulation
Here entropy generation and natural convection through a permeable geometry which is demonstrated in Fig. 1, has been modeled. Ferrofluid with properties of Table 1 was considered as
carrier fluid. Viscosity of ferrofluid is function of B which is mentioned in below formulation [37]. Magnetic field is imposed in x
direction. Buoyancy forces are estimated by Boussinesq model.
Boundary condition for inner elliptic wall is uniform heat flux
and outer sinusoidal kept in cold temperature. To enforce the porous space terms in governing equations, non-Darcy model was
used. Considering two dimensional flow yields below formulation:
@ v @u
þ
¼0
@y @x
ð1Þ
Bx ; By ¼ Bo ðcosc; sincÞ;
h
¼ rnf By v Bx
qnf @u
v þ u @u
@y
@x
qnf
@v
@y
k
nf
qC p nf
v þ @@xv u
lnf
¼
K
v þ lnf
þBx uBy rnf
@2T @2T
þ
@x2 @y2
!
B2y rnf u
@P
@x
@2 v
@x2
@P
@y
lnf
K
uþ
2
þ @@yv2 þ qnf g ðT
B2x
@2 u
@y2
i
2
þ @@x2u lnf
ð2Þ
T c Þbnf
ð3Þ
v rnf ;
@T
@T
¼ u
þv
@x
@y
ð4Þ
Ferrofluid properties can be found by using below six formulas:
RR ¼ ks kf ;
þ2/RRþ2kf þks
kf
kn f ¼
/RRþ2k þks
ð5Þ
f
lnf ¼ 0:035B2 þ 3:1B 27886:4807/2 þ 4263:02/ þ 316:0629 e
qnf ¼ þqs / þ ð1 /Þqf
1þ
h
qC p
1
f
qC p
s
ð6Þ
ð7Þ
i
1
1 / ¼ qC p nf qC p f
rnf
3ð@ 1Þ/
¼
þ 1; rs =rf ¼ @
rf ð@ þ 2Þ þ ð1 @Þ/
ðqbÞnf ¼ /ðqbÞs þ ð1
0:01T
ð8Þ
ð9Þ
/ÞðqbÞf
ð10Þ
By using Eq. (11), we could remove pressure terms and Eq. (12)
help us to present equation in dimensionless forms:
v¼
Fig. 1. Porous enclosure under the influence of imposed B.
wx ; uy
1
v x ¼ x;
DT ¼ kf Lq00 ; ðT
ð11Þ
T Þc ¼ HDT; u ¼ af U=L;
ð12Þ
ðx; yÞ ¼ LðX; Y Þ; v ¼ af V=L;
Table 1
Details of Fe3O4 and H2O.
Cp (J/kg K)
b 105 (K 1)
r (Xm) 1
k (W/mK)
q (kg/m3)
u ¼ wy ;
Fe3O4
H2O
670
1.3
25,000
6
5200
4179
21
0.05
0.613
997.1
Table 2
Obtained Nuav e for mesh analysis when at / ¼ 0:04,Da ¼ 100; Ha ¼ 40; and Ra ¼ 104 .
151 51
1.6889
181 61
1.6971
211 71
1.7076
241 81
1.7085
271 91
1.7094
148
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Ra=104
0.0018
0.0016
0.0014
0.0012
0.001
0.0008
0.0006
0.0004
0.0002
0.0001
6E-05
5.94515E-05
1.5E-05
4.5E-06
2.5E-06
3
2.5
2
1.5
1
0.5
Sgen,f
0.5
0.4
0.3
0.2
0.1
0.01
0.00085
0.0008
0.00075
0.0007
0.00065
0.0006
0.00055
0.0005
0.00045
0.0004
0.00035
0.0003
0.00025
0.0002
0.00015
0.0001
5E-05
0.00038
0.00036
0.00034
0.00032
0.0003
0.00028
0.00026
0.00024
0.00022
0.0002
0.00018
0.00016
0.00014
0.00012
0.0001
8E-05
6E-05
4E-05
2E-05
0.04
0.038
0.036
0.034
0.032
0.03
0.028
0.026
0.024
0.022
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
Be
9.5E-06
9E-06
8.5E-06
8E-06
7.5E-06
7E-06
6.5E-06
6E-06
5.5E-06
5E-06
4.5E-06
4E-06
3.5E-06
3E-06
2.5E-06
2E-06
1.5E-06
1E-06
5E-07
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Sgen,th
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.7
0.65
0.6
0.5
0.45
0.4
0.3
0.2
0.1
0.05
0.01
Xd
Sgen,p
Sgen,M
Isotherms
Streamlines
Ra=103
0.999
0.998
0.997
0.996
0.995
0.994
0.993
0.992
0.991
0.99
0.989
0.988
0.987
0.986
0.985
0.984
0.983
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
Fig. 2. Effect of Ra on first and second law analysis at Ha ¼ 1; / ¼ 0:04; Da ¼ 0:01.
0.12
0.1
0.08
0.06
0.04
0.03
0.02
0.01
0.007
0.003
0.002
0.0008
0.0002
5.2E-05
1E-05
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.03
0.02
0.01
0.005
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.8
0.76
0.72
0.68
0.64
0.56
0.52
0.48
0.44
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
149
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Ra=103
Ra=104
0.06
0.05
0.04
0.03
0.02
0.01
0.7
0.6
0.5
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
1.3E-05
1.2E-05
1.1E-05
1E-05
9E-06
8E-06
7E-06
6E-06
5E-06
4E-06
3E-06
2E-06
1E-06
0.00115
0.00105
0.00095
0.00085
0.00075
0.0007
0.00065
0.0006
0.00055
0.0005
0.00045
0.0004
0.00035
0.0003
0.00025
0.0002
0.00015
0.0001
5E-05
Sgen,f
Be
0.00022
0.0002
0.00018
0.00016
0.00014
0.00012
0.0001
8E-05
6E-05
4E-05
2E-05
1E-05
1E-06
0.021
0.02
0.019
0.018
0.017
0.016
0.015
0.014
0.013
0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
Sgen,th
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.25
0.15
0.05
Xd
Sgen,p
Sgen,M
Isotherms
Streamlines
0.55
0.5
0.4
0.3
0.2
0.1
0.07
0.05
0.02
0.0001
9E-05
8E-05
7E-05
6E-05
5E-05
4E-05
3E-05
2.5E-05
2E-05
1.5E-05
1E-05
5E-06
9.5E-07
5.5E-07
2E-07
1.2E-07
3.5E-08
1.4E-08
0.75
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.25
0.15
0.1
0.05
0.025
0.9998
0.999737
0.9995
0.999
0.9985
0.998
0.9975
0.997
0.9965
200
190
180
160
140
120
110
100
80
60
40
20
10
Fig. 3. Effect of Ra on first and second law analysis at Ha ¼ 40; / ¼ 0:04; Da ¼ 0:01.
0.01
0.008
0.006
0.004
0.003
0.002
0.001
9E-05
4.5E-05
1.8E-05
1E-05
6E-06
3.5E-06
1.5E-06
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.02
0.999283
0.994379
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
0.76
0.72
0.68
0.64
0.6
200
190
180
170
150
130
120
110
90
70
60
50
40
30
10
150
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Sgen,p
0.000115
0.00011
0.000105
0.0001
9.5E-05
9E-05
8.5E-05
8E-05
7.5E-05
7E-05
6.5E-05
6E-05
5.5E-05
5E-05
4E-05
3E-05
2E-05
1.5E-05
1E-05
5E-06
1.05E-06
1E-06
9.5E-07
9E-07
8.5E-07
8E-07
7.5E-07
7E-07
6.5E-07
6E-07
5.5E-07
5E-07
4.5E-07
4E-07
3.5E-07
3E-07
2.5E-07
2E-07
1.5E-07
1E-07
5E-08
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.0025
0.0023
0.0021
0.0019
0.0015
0.0013
0.0011
0.001
0.0009
0.0008
0.0007
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
2.2E-05
2.1E-05
2E-05
1.9E-05
1.8E-05
1.7E-05
1.6E-05
1.5E-05
1.4E-05
1.3E-05
1.2E-05
1.1E-05
1E-05
9E-06
8E-06
7E-06
6E-06
5E-06
4E-06
3E-06
2E-06
1E-06
Sgen,th
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
7
6
5
4
3
2
1
Be
Sgen,M
Isotherms
Streamlines
2.2
2
1.5
1
0.5
0.1
Sgen,f
Ra=104
Xd
Ra=103
0.008
0.007
0.006
0.005
0.004
0.0035
0.003
0.0025
0.002
0.0015
0.001
0.0005
0.0003
0.0001
5.6E-05
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.03
0.995
0.99
0.985
0.98
0.975
0.97
0.965
0.96
0.955
0.95
0.945
0.94
0.935
0.93
0.925
0.92
0.915
0.91
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
Fig. 4. Effect of Ra on first and second law analysis at / ¼ 0:04; Ha ¼ 1; Da ¼ 100.
0.28
0.26
0.24
0.22
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0.006
0.0027
0.001
0.0004
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.01
0.005
0.003
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
151
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
0.00026
0.00024
0.00022
0.0002
0.00018
0.00016
0.00014
0.00012
0.0001
8E-05
6E-05
4E-05
2E-05
1.5E-09
1.4E-09
1.3E-09
1.2E-09
1.1E-09
1E-09
9E-10
8E-10
7E-10
6E-10
5E-10
4E-10
3E-10
2E-10
1E-10
0.7
0.55
0.45
0.35
0.25
0.2
0.15
0.1
0.05
0.023
0.021
0.019
0.017
0.015
0.013
0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
1.3E-07
1.2E-07
1.1E-07
1E-07
9E-08
8E-08
7.5E-08
6.5E-08
6E-08
5.5E-08
5E-08
4.5E-08
4E-08
3.5E-08
3E-08
2.5E-08
2E-08
1.5E-08
1E-08
5E-09
Sgen,th
0.7
0.65
0.6
0.55
0.5
0.45
0.35
0.25
0.15
0.05
0.6
0.5
0.4
0.3
0.2
0.1
0.05
Be
0.065
0.06
0.05
0.04
0.03
0.02
0.01
0.005
0.001
Sgen,f
Ra=104
Xd
Sgen,p
Sgen,M
Isotherms
Streamlines
Ra=103
0.00011
9E-05
7E-05
5E-05
4E-05
3E-05
2E-05
1E-05
1.1E-06
6E-07
2E-07
6E-08
3.2E-08
0.75
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.15
0.05
0.01
0.9998
0.9995
0.999
0.9985
0.998
0.9975
0.997
0.9965
0.996
0.9955
0.9945
0.9925
0.9915
200
180
160
140
130
120
110
100
90
80
70
60
50
40
30
20
10
Fig. 5. Effect of Ra on first and second law analysis at Ha ¼ 40; / ¼ 0:04; Da ¼ 100.
0.0115
0.0095
0.0075
0.0055
0.005
0.0045
0.004
0.0035
0.003
0.0025
0.002
0.0015
0.001
0.0005
0.0001
6E-05
3E-05
9E-06
0.7
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
0.78
0.76
0.74
0.72
0.68
0.64
0.6
0.56
200
190
180
170
160
150
140
130
120
110
100
90
80
70
50
30
10
152
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Fig. 6. Changes of Nuav e respect to Ha; Ra; Da at / ¼ 0:04.
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Fig. 7. Changes of Be respect to Ha; Ra; Da at / ¼ 0:04.
153
154
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Fig. 8. Changes of X d respect to Ha; Ra; Da at / ¼ 0:04.
155
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Therefore, last formulations are obtained as below:
V
@2H
@H
@H
þU
¼
@Y
@X
@Y
2
þ
!
@2H
@X
2
ð13Þ
WXX þ WYY ¼ X
ð14Þ
2
Pr A5 A2
þ @@XX2
X
Da A1 A4
h i
2
2
A
A
þHa2 Pr A61 A24
V Y ðsincÞðcoscÞ þ ðcoscÞU X ðsincÞ þ ðsincÞ U Y
V X ðcoscÞ
A A2
þRa Pr @@XH A3 A22 ¼ U @@XX þ @@YX V
Pr
4. Results and discussion
A5 A2
A1 A4
@2 X
@Y 2
1 4
ð15Þ
The above three equations, following parameters have been
employed:
Da ¼ LK2 ; Ra ¼ gbf q} L4 =ðkf tf af Þ;
qffiffiffiffiffiffiffiffiffiffiffiffiffi
ðq C Þ
A2 ¼ ðqCPP Þnf ; Ha ¼ LB0 rf =lf ;
f
ðqbÞnf
ðqbÞf
A1 ¼
qnf
qf
;
A4 ¼
knf
kf
; A6 ¼ rnf
f
A3 ¼
ð16Þ
l
; A5 ¼ lnf ; Pr ¼ tf =af ;
f
r
Based on Fig. 1, boundary conditions can be summarized as:
W ¼ 0:0
@H
@n
on every surfaces
¼ 1:0
on elliptic wall
H ¼ 0:0
ð17Þ
Nuav e ¼ 1:99 þ 0:14Da þ 0:25logðRaÞ
þ0:079Da logðRaÞ
on outer wall
Nuloc and Nuav e are determined from:
In current paper, we calculated entropy generation, Bejan number, Nusselt number and exergy loss:
Sgen;total
In current manuscript, insertions of permeable medium and
dispersing magnetic nanoparticles into carrier fluid have been
applied to help the convection in appearance of magnetic force.
Characteristics of nanomaterial were predicted with assumption
of single phase model and final equations were solved via new
numerical technique. Simulations based of CVFEM were conduct
to demonstrate the roles of permeability, Hartmann and buoyancy
forces. Not only the heat transfer but also entropy generation and
exergy drops are our goal factors in current paper.
Outputs of exergy drop, entropy generation, w and temperature
contours were reported in Figs. 2–5. As buoyancy force is augmented vertical velocity of nanomaterial enhances (jwmax j augments) and more heat is transmitted to upper side of domain.
Presence of thermal plume can prove this fact, too. Obtaining
greater heat transfer cause exergy loss to decline. Imposing magnetic field yields reduction in velocity. Therefore, entropy generation augments with growth of Ha. Sgen,p, Sgen,f and Sgen,M act as
same as each other while their behavior has inverse relationship
with Sgen,th. The contours show that when permeability has been
enhanced, although the convection augments, reduction of exergy
loss has been observed. Nuav e ; Be and X d as functions of the Da, Ra
and Ha were demonstrated in Figs. 6–8. Besides, below formulas
can make sense for relationship of variables and outputs.
"
2 #
2
2
@v
@u @ v
@u
¼þ 2 2
þ
þ2
þ
@y @x
@x
@y
T
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}
lnf
X d ¼ 45:62
0:14Da Ha
1:86Da
0:3Ha
ð22Þ
0:23logðRaÞHa
2:89logðRaÞ þ 4:3Ha
ð23Þ
0:65Da logðRaÞ þ 1:83Da Ha þ 2:73logðRaÞHa
Be ¼ 0:041 logðRaÞHa þ 0:94
7:8 10
3
logðRaÞDa
0:0581 logðRaÞ
3
0:01 Da þ 9:4 10 Da Ha þ 0:044Ha
ð24Þ
Sgen;f
2
1
B2
2 0
lnf
2
2
þ rnf v
þ
v þu
KT
T ffl} |fflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflffl}
|fflfflfflfflfflfflfflffl{zfflfflfflfflfflfflffl
Sgen;M
h
1
Sgen;th ¼ Be
Sgen;total
Nuav e ¼
1
S
Z
2 i
þ ðT x Þ þ T y knf T 2
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}
2
Sgen;th
s
Nuloc ds; Nuloc ¼
0
Sgen;P
ð18Þ
ð19Þ
1!
knf
4
1 knf
1 þ Rd
3
h kf
kf
X d ¼ T 0 Sgen;total
ð20Þ
ð21Þ
3. Method, validation and mesh
In recent eight years, Sheikholeslami [37] developed innovate
numerical technique (CVFEM) in which lower computational cost
needs for solving heat transfer problems. He employed this method
for various fields. He published his experiences as nice reference
book [37]. Each numerical code needs to be verified. In order to
do not write repeated text about validation, we refer the reader
to previous published article [38] which is done via current code.
Accordingly, developed code has high accuracy. Besides, to make
sure independence of outputs to mesh size, different configurations have been taken into account and one example exists in
Table 2.
Hot surface temperature declines with rise of permeability. So,
rate of heat transfer enhances and Bejan number declines with rise
of Da. An increase in Ha causes to decline in convection flow of
nanomaterial and help to augmentation of exergy drop. Thus, Be
is in direct relationship with Hartmann number. Greater Be has
been obtained in lower Ra when conduction is more pronounced.
5. Conclusions
In current article, results of thermal behavior, exergy drop and
entropy generation of nanomaterial within a porous domain have
been demonstrated. Domain is affected by horizontal magnetic
field and inner elliptic is hot source. Changing of Darcy, Hartmann
and Rayleigh numbers has been simulated via CVFEM. Outputs
were reported as contours and good correlations. Outcomes prove
that Be goes up with rise of Hartmann but it declines with augment
of Ra and Da.
Conflict of interest
The author declares that there is no conflict of interest.
Acknowledgment
Dr. Tawfeeq Abdullah Alkanhal would like to thank Deanship of
Scientific Research at Majmaah University for supporting this work
under the Project Number No. 1440-49.
156
T.A. Alkanhal et al. / International Journal of Heat and Mass Transfer 136 (2019) 146–156
Author Contributions
Dr. Tawfeeq Abdullah Alkanhal preside the actual team works
start and generate the idea from the beginning till publication,
he establish the mathematical formulation, modeled the problem.
After modeling with his team he checked the result and wrote the
related section. Other authors thoroughly checked the mathematical modeling and English corrections. All authors finalized the
manuscript after its internal evaluation.
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