Begell House Inc.
Journal of Porous Media
JPM
1091-028X
19
2
2016
NUMERICAL ANALYSIS OF FORCED CONVECTION ENHANCEMENT INSIDE SINUSOIDAL WAVY CHANNELS FULLY FILLED WITH POROUS MEDIA
95-111
10.1615/JPorMedia.v19.i2.10
Fahad S.
Mansoor
University of Mosul
Amir S.
Dawood
Department of Mechanical Engineering, University of Mosul, Mosul, Iraq
porous media
wavy channels
elliptic grid generation
forced convection
non-Darcian flow
heat transfer enhancement
Forced convection heat transfer and fluid flow characteristics were numerically investigated inside wavy walled channels fully filled with homogeneous porous material. The effect of the amplitude and wavelength of the sinusoidal wavy surface was also studied for two models of wavy channels and compared to the flat-plate channel. The governing equations were solved on a nonorthogonal grid, which is generated by Poisson elliptic equations, based on the ADI method. The results showed that the surface waviness gives an increase in heat transfer compared to the flat surface, but not for all the cases of study. Hence, wavelength shortening reduces the rate of heat transferred especially for the small values of amplitude. Furthermore, the highest possible percentage of enhancement in heat transfer for the current study was about 18%.
LOCAL THERMAL NONEQUILIBRIUM EFFECTS ON NATURAL CONVECTION IN A POROUS CAVITY HEATED AND COOLED FROM THE SIDE IN A SPATIALLY SINUSOIDAL MANNER
113-129
10.1615/JPorMedia.v19.i2.20
Feng
Wu
School of Chemical Engineering, Northwest University, Taibai North Road 229, Xi'an 710069, China
Wenjing
Zhou
Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
local thermal nonequilibrium model
sinusoidal temperature profile
natural convection
porous medium
Steady non-Darcy natural convection in a rectangular cavity filled with a heat-generating porous medium is studied numerically by adopting the local thermal nonequilibrium (LTNE) model in this article. All of the walls of the enclosure are adiabatic except the left wall, which is partially heated and cooled with a sinusoidal temperature profile. The results show that, compared with the uniform boundary conditions, the sinusoidal boundary conditions enhance the heat transfer rate of porous cavity. Under the same boundary conditions, the LTNE and local thermal equilibrium models can lead to significant differences inflow patterns and temperature fields. When the periodicity parameter becomes large enough (N = 30), the uniform thermal boundary condition and sinusoidal thermal boundary condition have the same effects on heat transfer of the porous cavity. A high interphase heat transfer coefficient (H = 1000) can lead to faster reduction of the heat transfer of the porous cavity with the increase of periodicity parameter. A high thermal conductivity ratio (γ = 1) can slow down the reduction speed of convective heat transfer when the periodicity parameter (N) increases.
TRANSPIRATION COOLING WITH LOCAL THERMAL NONEQUILIBRIUM: MODEL COMPARISON IN MULTIPHASE FLOW IN POROUS MEDIA
131-153
10.1615/JPorMedia.v19.i2.30
Franz
Lindner
Department of Aerospace Engineering, Institute for Thermodynamics, University of the Federal Armed Forces Munich, 85577 Neubiberg, Germany
Philipp
Nuske
Department of Hydromechanics and Modelling of Hydrosystems, University of Stuttgart, 70569 Stuttgart, Germany
Kilian
Weishaupt
Department of Hydromechanics and Modelling of Hydrosystems, University of Stuttgart, 70569 Stuttgart, Germany
Rainer
Helmig
Department of Hydromechanics and Modelling of Hydrosystems, University of Stuttgart, 70569 Stuttgart, Germany
Christian
Mundt
Department of Aerospace Engineering, Institute for Thermodynamics, University of the Federal Armed Forces Munich, 85577 Neubiberg, Germany
Michael
Pfitzner
Department of Aerospace Engineering, Institute for Thermodynamics, University of the Federal Armed Forces Munich, 85577 Neubiberg, Germany
porous evaporator
transpiration cooling
multiphase flow
phase change
local thermal nonequilibrium
mixture model
fully coupled model
This article investigates the evaporation process in porous media during transpiration cooling. This means that a strong heat source fully evaporates a high liquid flux, leading to complex flow situations. This multiphase flow with phase change setting is simulated with two different models, implemented in MATLAB and DuMu, a free and open source simulator, respectively. These models use different mathematical and numerical schemes but are able to simulate local thermal nonequilibrium. For a sample 1D case, the models are tested against one another and compared to results from the literature. Considerable differences to the published results are found, but the two models in this work show almost the same behavior, without any calibration employed.
EFFECT OF INITIAL STRESS ON A THERMOELASTIC MEDIUM WITH VOIDS AND MICROTEMPERATURES
155-172
10.1615/JPorMedia.v19.i2.40
Mohamed I. A.
Othman
Department of Mathematics, Faculty of Science, P.O. Box 44519, Zagazig University, Zagazig, Egypt; Department of Mathematics, Faculty of Science, Taif University, Taif, Saudi Arabia
R. S.
Tantawi
Department of Mathematics, Faculty of Science, Zagazig University, Zagazig, Egypt
Elsayed M.
Abd-Elaziz
Department of Mathematics, Faculty of Science, Zagazig University, Zagazig, Egypt
microtemperature
normal mode method
initial stress
voids
thermoelasticity
The purpose of this article is to study the effect of initial stress on a thermoelastic half-space with voids and microtemperatures. Normal mode analysis has been used to solve the problem. The components of displacements, stresses, first heat flux moment tensor, and temperature change are computed numerically. Numerically stimulated results of the resulting quantities in the presence and absence of the initial stress and void parameters are shown graphically
A NOTE ON ENTROPY GENERATION IN MHD FLOW OVER A VERTICAL PLATE EMBEDDED IN A POROUS MEDIUM WITH ARBITRARY SHEAR STRESS AND RAMPED TEMPERATURE
175-187
10.1615/JPorMedia.v19.i2.50
Arshad
Khan
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia 81310, Skudai, Malaysia; Department of Computer Science/IT Sarhad University of Science & IT, Peshawar Khyber Pakhtunkhwa Pakistan
Ilyas
Khan
Ton Duc Thang University
Farhad
Ali
City University of Science and Information Technology, Peshawar
Sharidan
Shafie
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia
81310 UTM Johor Bahru, Johor, Malaysia
wall shear stress
ramped temperature
MHD
porous medium
entropy generation
Bejan number
This note provides an exact analysis of unsteady free convection flow of viscous fluid past a vertical plate with arbitrary shear stress and ramped wall temperature. The fluid is considered to be electrically conducting and passing through a porous medium. Equations governing the problem are first written in dimensionless form and then solved for the exact solutions using the Laplace transform method. The graphs of velocity, entropy generation, and Bejan number are plotted for various parameters of interest. It is found that velocity and entropy generation decrease with increasing wall shear stress in cases of both ramped and constant wall temperature. It is also observed that Bejan number increases with increasing wall shear stress.