Begell House Inc.
Journal of Porous Media
JPM
1091-028X
21
4
2018
EFFECT OF THE METALLIC FOAM HEAT SINK SHAPE ON THE MIXED CONVECTION JET IMPINGEMENT COOLING OF A HORIZONTAL SURFACE
295-309
10.1615/JPorMedia.v21.i4.10
Nawaf H.
Saeid
Flow Modeling and Simulation Research Cluster, Universiti Teknologi Brunei, Tungku Link,
Gadong, BE 1410, Brunei Darussalam
Nurul
Hasan
Flow Modeling and Simulation Research Cluster, Universiti Teknologi Brunei, Tungku Link,
Gadong, BE 1410, Brunei Darussalam
Mohamed Hairol Bin Hj Mohd.
Ali
Flow Modeling and Simulation Research Cluster, Universiti Teknologi Brunei, Tungku Link,
Gadong, BE 1410, Brunei Darussalam
mixed convection
jet impingement cooling
porous media
numerical study
The effects of six different shapes of aluminum foam heat sinks attached to a horizontal heated surface are investigated numerically under the slot-jet impingement cooling. Various aluminum foam heat sink shapes are considered for easy manufacturing, such as rectangle, elliptic, trapezoidal, opposite trapezoidal, triangle, and opposite triangle. The jet inlet flow is in the vertical direction from the top, which leads to the opposing mixed convection mode condition. The air flow through the aluminum foam heat sinks is modeled using the porous media model. The results are presented for two different types of aluminum foams. The governing parameters are grouped into Reynolds number, Grashof number, and the metallic foam heat sink shape and properties (inertial resistance factor, permeability, and porosity). The results show that the cooling process enhancement can be achieved by attaching any one of the shapes and both types of the aluminum foam heat sinks considered. It is found that the most effective heat sink shape depends on the flow conditions (Re, Gr, and foam shape and properties). The results presented show the effects of the shape of the metal foam on the heat dissipation for different flow conditions. The results also show the superiority of the convex-shape heat sinks under the forced convection mode conditions. On the other hand, the results show that the concave-shape heat sinks are more effective than the convex ones under the mixed convection mode conditions.
NUMERICAL AND EXPERIMENTAL STUDY OF COMPRESSIBLE GAS FLOW THROUGH A POROUS/FLUID–COUPLED AREA
311-328
10.1615/JPorMedia.v21.i4.20
Xiwen
Zhang
Department of Engineering Mechanics, School of Aerospace, Tsinghua University, Beijing 100084, China
Zhaohui
Yao
Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, P.R. China
Pengfei
Hao
Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, P.R. China
porous/fluid-coupled area
compressible gas flow
non-Darcy flow
Numerical simulations and theoretical investigations of fluid flow and heat transfer in porous/fluid-coupled areas have increased greatly in recent years. Scant research has concentrated on compressible gas flow in porous/fluid-coupled areas. First, an effective experiment method is proposed that can be used to accurately measure the permeability and inertial coefficient of porous media when gas flows at a high speed and high differential pressure. Using the method, the parameters of the non-Darcy flow through polyvinyl formal porous materials were tested in an actual experiment. Additionally, modified governing equations were used to solve the non-Darcy flow in porous media and turbulent flow in compressible air–coupled regimes. A method to determine the source terms for flow in porous media is presented. A robust numerical scheme was used to discretize the equations, and time-dependent boundary conditions were used to treat the boundary conditions. A detailed numerical and experimental investigation of compressible gas flow in a straight, round pipe with porous/fluid-coupled areas and backward- and forward-facing steps is given. The computational results were in strong agreement with the experimental data.
REPRESENTING PORE SHAPES BY APPROPRIATE POLYGONS IN PORE NETWORK MODELS
329-341
10.1615/JPorMedia.v21.i4.30
Jian
Hou
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao,
Shandong 266580, China; School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China
Bei
Wei
School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580,
China
Kang
Zhou
School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580,
China
Qingjun
Du
School of Geosciences, China University of Petroleum, Qingdao, Shandong 266580, China
pore network model
cross section
shape factor
nonunique polygon
Three new shape characterization techniques for the pore network model are developed so that capillary behavior can
be predicted more accurately. Given a shape factor and inscribed radius, the C-T-Q (circles, arbitrary triangles, and quadrangles) characterization is proposed based on the C-T-S (circles, arbitrary triangles, and squares) characterization. Instead of squares, irregular quadrangles are used to represent pore shapes. The nonunique convex polygon characterization technique uses a pore's area and perimeter to create a mathematical model. The area and perimeter are kept exactly the same as those of the actual shape. Finally, given the inscribed radius, area, and perimeter, the polygon's shape characterization is improved by treating concave cross sections specifically. Compared with the traditional method, the new methods can describe capillary behavior more accurately and can be used to make the structure of a pore network model more realistic.
DOUBLE-DIFFUSIVE MIXED CONVECTION IN A COMPOSITE POROUS ENCLOSURE WITH ARC-SHAPED MOVING WALL: TORTUOSITY EFFECT
343-362
10.1615/JPorMedia.v21.i4.40
Muneer A.
Ismael
Mechanical Engineering Department, Engineering College, University of Basrah, Basrah
61004, Iraq
double-diffusion
porous layer
tortuosity
lid-driven
irregular boundary
A double-diffusive mixed convection in a lid-driven partially layered porous enclosure is addressed numerically in this paper. The mass diffusivity coefficient of the porous medium is determined based on the tortuosity and porosity model. The left wall is kept at constant hot temperature and high concentration. The right wall is arc shaped, being driven, and kept at constant cold temperature and low concentration. The horizontal walls are thermally insulated. The studied pertinent parameters are the Lewis number (0.5 ≤ Le ≤ 5), buoyancy ratio (–7 ≤ N ≤ 7), arc-shaped wall speed (–100 ≤ ω ≤ 100), and thermal Rayleigh number (103 ≤ Ra ≤ 106). The other fixed parameters are the Prandtl number, Pr = 0.71 (air), Darcy number, Da = 10-3, and porous layer thickness Xp = 0.5. The results show that for Ra ≥ 105, there is a significant effect of considering the real coefficient of mass diffusivity on both heat and mass transfer. Interesting competitions among the buoyancy ratio, direction of the arc-shaped wall speed, and Lewis number are recorded and discussed in detail.
NONSIMILAR SOLUTION OF UNSTEADY MIXED CONVECTION FLOW NEAR THE STAGNATION POINT OF A HEATED VERTICAL PLATE IN A POROUS MEDIUM SATURATED WITH A NANOFLUID
363-388
10.1615/JPorMedia.v21.i4.50
Abdullah A.
Abdullah
Department of Mathematical Sciences, Umm Al-Qura University, Makkah 24382, Saudi
Arabia
Fouad S.
Ibrahim
Department of Mathematics, University College, Umm Al-Qura University, Makkah, Saudi
Arabia; Department of Mathematics, Faculty of Science, Assiut University, Assiut, Egypt
Ali J.
Chamkha
Mechanical Engineering Department, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, P.O. Box
10021, Ras Al Khaimah, United Arab Emirates
boundary layer
unsteady mixed convection
nanofluids
stagnation region
impulsive motion
non-Darcian porous media
local nonsimilar solution
This article studies the effects of Brownian motion and thermophoresis on unsteady mixed convection flow near the
stagnation-point region of a heated vertical plate embedded in a porous medium saturated by a nanofluid. The plate
is maintained at a variable wall temperature and nanoparticle volume fraction. The presence of a solid matrix, which exerts first and second resistance parameters, is considered in this study. A suitable coordinate transformation is introduced and the resulting governing equations are transformed and then solved numerically using the local nonsimilarity method and the Runge-Kutta shooting quadrature. The effects of various governing parameters on the flow and heat and mass transfer on the dimensionless velocity, temperature, and nanoparticle volume fraction profiles as well as the skin-friction coefficient, Nusselt number, and the Sherwood number are displayed graphically and discussed to illustrate interesting features of the solutions. The results indicate that as the values of the thermophoresis and Brownian motion parameters increase, the local skin-friction coefficient increases whereas the Nusselt number decreases. Moreover, the Sherwood number increases as the thermophoresis parameter increases, and decreases as the Brownian motion parameter increases. On the other hand, the unsteadiness parameter and the resistance parameters enhance the local skin-friction coefficient, local Nusselt number, and the local Sherwood number.