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1.
The effect of the presence of an isotropic solid matrix on the forced convection heat transfer rate from a flat plate to power-law non- Newtonian fluid-saturated porous medium, has been investigated. Numerical results are presented for the distribution of velocity and temperature profiles within the boundary layer. The effects of the flow index, first-order and second-order resistance on the velocity, and temperature profiles are discussed. The missing wall values of the velocity and thermal functions are tabulated. 相似文献
2.
M. F. El-Amin S. Sun M. A. El-Ameen Y. A. Jaha Rama Subba Reddy Gorla 《Transport in Porous Media》2011,86(3):965-972
A boundary layer analysis was presented to study the non-Darcy-free convection of a power-law fluid over a non-isothermal
two-dimensional body embedded in a porous medium. The Ostwald-de Waele power-law model was used to characterize the non-Newtonian
fluid behavior. Similarity solutions were obtained with variations in surface temperature or surface heat flux. In view of
the fact that most of the non-Newtonian fluids have large Prandtl numbers, this study was directed toward such fluids. The
effects of the porous medium parameters, k
1 and k
2, body shape parameter, m, and surface thermal variations parameter, p, as well as the power-law index, n, were examined. 相似文献
3.
In this study, laminar boundary layer flow over a flat plate embedded in a fluid-saturated porous medium in the presence of
viscous dissipation, inertia effect and suction/injection is analyzed using the Keller box finite difference method. The flat
plate is assumed to be held at constant temperature. The non-Darcian effects of convection, boundary and inertia are considered.
Results for the local heat transfer parameter and the local skin friction parameter as well as the velocity and temperature
profiles are presented for various values of the governing parameters. The non-Darcian effects are shown to decrease the velocity
and to increase the temperature. It is also shown that the local heat transfer parameter and the local skin friction parameter
increase due to suction of fluid while injection reverses this trend. It is disclosed that the effect of the viscous dissipation
for negative values of Ec (T
w
< T
∞) is to enhance the heat transfer coefficient while the opposite is true for positive values of Ec (T
w
> T
∞). The results are compared with those available in the existing literature and an excellent agreement is obtained. 相似文献
4.
5.
In this note, we reply to the comments by Rees and Magyari (2007) on our article (Aydin and Kaya 2007). They mainly stated
that the thermal boundary conditions we defined at the edge of the boundary layer were incompatible with the energy equation.
This is questionable and therefore we will discuss it below. They disclosed that our results were in error. However, this
is quite misleading. Scientifically, they cannot reach such a conclusion without comparing our results with what they thought
to be correct. In fact, this misleading and unproven statement will be shown not to be correct in the following. 相似文献
6.
A boundary layer analysis has been presented for the interaction of mixed convection with thermal radiation in laminar boundary flow from a vertical wedge in a porous medium saturated with a power-law type non-Newtonian fluid. The fluid considered is a gray medium, and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The transformed conservation laws are solved numerically for the case of variable surface temperature conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented. 相似文献
7.
The problem of melting from a vertical flat plate embedded in a porous medium is studied. The main focus is to determine the effect of mixed convection flow in the liquid phase on the melting phenomenon. Both aiding and opposing flows are considered. The conservation equations that govern the problem are reduced to a system of nonlinear ordinary differential equations. The governing equations are solved numerically. Numerical results are obtained for the temperature and flow fields in the melting region. The melting phenomenon decreases the local Nusselt number at the solid–liquid interface. 相似文献
8.
This article considers the problem of mixed convection stagnation-point flow towards a vertical plate embedded in a porous
medium with prescribed surface heat flux. It is assumed that the free stream velocity and the surface heat flux vary linearly
from the stagnation point. Using a similarity transformation, the governing system of partial differential equations is transformed
into a system of ordinary differential equations, before being solved numerically by a finite-difference method. The features
of the flow and the heat transfer characteristics are analyzed and discussed. It is found that dual solutions exist for both
buoyancy assisting and opposing flows. 相似文献
9.
The problem of unsteady free convection heat transfer from a one-dimensional (parallel) flow along an infinite vertical flat
plate embedded in a thermally stratified fluid-saturated porous medium is considered. Flows are induced by a sudden change
in the arbitrary temporal plate temperature. By a formal reduction of the corresponding boundary value problems to well-known
Fourier heat conduction problems, analytical solutions of the Darcy and energy equations are obtained. Several special cases
are discussed in detail. 相似文献
10.
The problem of the free convection boundary-layer flow over a semi-infinite vertical flat surface in a porous medium is considered,
in which the surface temperature has a constant value T1 at the leading edge, where T1 is above the ambient temperature, and takes a value T2 at a given distance L along the surface, varying linearly between these two values and remaining constant afterwards. Numerical solutions of the
boundary-layer equations are obtained as well as solutions valid for both small and large distance along the surface. Results
are presented for the three cases, when the temperature T2 is greater, equal or less than the ambient temperature T∞. In the first case, T2 > T∞, a boundary-layer flow develops along the surface starting with a flow associated with the temperature difference T1 − T∞ at the leading edge and approaching a flow associated with the temperature difference T2 − T∞ at large distances. In the second case, T2 = T∞, the convective flow set up on the initial part of the surface drives a wall jet in the region where the surface temperature
is the same as ambient. In the final case, T2 < T∞, a singularity develops in the numerical solution at the point where the surface temperature becomes T∞. The nature of this singularity is discussed. 相似文献
11.
Fethi Kamışlı 《Transport in Porous Media》2009,80(2):345-371
The flow of an incompressible Newtonian fluid confined in a planar geometry with different wall temperatures filled with a
homogenous and isotropic porous medium is analyzed in terms of determining the unsteady state and steady state velocities,
the temperature and the entropy generation rate as function of the pressure drop, the Darcy number, and the Brinkman number.
The one-dimensional approximate equation in the rectangular Cartesian coordinates governing the flow of a Newtonian fluid
through porous medium is derived by accounting for the order of magnitude of terms as well as accompanying approximations
to the full-blown three-dimensional equations by using scaling arguments. The one-dimensional approximate energy and the entropy
equations with the viscous dissipation consisting of the velocity gradient and the square of velocity are derived by following
the same procedure used in the derivation of velocity expressions. The one-dimensional approximate equations for the velocity,
the temperature, and the entropy generation rate are analytically solved to determine the velocity, the temperature, and the
entropy distributions in the saturated porous medium as functions of the effective process parameters. It is found that the
pressure drop, the Darcy number, and the Brinkman number affect the temperature distribution in the similar way, and besides
the above parameters, the irreversibility distribution ratio also affects the entropy generation rate in the similar way. 相似文献
12.
In this investigation, we intend to present the influence of the prominent Soret effect on double-diffusive free convection heat and mass transfer in the boundary layer region of a semi-infinite inclined flat plate in a nanofluid saturated non-Darcy porous medium. The transformed boundary layer ordinary differential equations are solved numerically using the shooting and matching technique. Consideration of the nanofluid and the coupled convective process enhanced the number of non-dimensional parameters considerably thereby increasing the complexity of the present problem. A wide range of parameter values are chosen to bring out the effect of Soret parameter on the free convection process with varying angle of inclinations making the wall geometry from vertical to horizontal plate. The effects of angle of inclination and Soret parameter on the flow, heat and mass transfer coefficients are analyzed. The numerical results obtained for the velocity, temperature, volume fraction, and concentration profiles, local wall temperature, local nanoparticle concentration, and local wall concentration reveal interesting phenomenon, and some of these qualitative results are presented through the plots. 相似文献
13.
Transport in Porous Media - 相似文献
14.
The steady laminar incompressible free convective flow of a nanofluid over a permeable upward facing horizontal plate located
in porous medium taking into account the thermal convective boundary condition is studied numerically. The nanofluid model
used involves the effect of Brownian motion and the thermophoresis. Using similarity transformations the continuity, the momentum,
the energy, and the nanoparticle volume fraction equations are transformed into a set of coupled similarity equations, before
being solved numerically, by an implicit finite difference numerical method. Our analysis reveals that for a true similarity
solution, the convective heat transfer coefficient related with the hot fluid and the mass transfer velocity must be proportional
to x
−2/3, where x is the horizontal distance along the plate from the origin. Effects of the various parameters on the dimensionless longitudinal
velocity, the temperature, the nanoparticle volume fraction, as well as on the rate of heat transfer and the rate of nanoparticle
volume fraction have been presented graphically and discussed. It is found that Lewis number, the Brownian motion, and the
convective heat transfer parameters increase the heat transfer rate whilst the thermophoresis decreases the heat transfer
rate. It is also found that Lewis number and the convective heat transfer parameter enhance the nanoparticle volume fraction
rate whilst the thermophoresis parameter decreases nanoparticle volume fraction rate. A very good agreement is found between
numerical results of the present article for special case and published results. This close agreement supports the validity
of our analysis and the accuracy of the numerical computations. 相似文献
15.
Numerical analysis is performed to examine laminar free convective of a nanofluid along a vertical wavy surface saturated
porous medium. In this pioneering study, we have considered the simplest possible boundary conditions, namely those in which
both the temperature and the nanoparticle fraction are constant along the wall. Non-similar transformations are presented
for the governing equations and the obtained PDE are then solved numerically employing a fourth order Runge–Kutta method with
shooting technique. A detailed parametric study (nanofluid parameters) is performed to access the influence of the various
physical parameters on the local Nusselt number and the local Sherwood number. The results of the problem are presented in
graphical forms and discussed. 相似文献
16.
The method of non-similarity solution is used to study the influence of thermal dispersion on combined convection from vertical surfaces in a porous medium saturated with a power-law type non-Newtonian fluid. The coefficient of thermal diffusivity has been assumed to be the sum of molecular diffusivity and the dispersion thermal diffusivity due to mechanical dispersion. The transformed conservation laws are solved numerically for the case of variable surface heat flux conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented. 相似文献
17.
Effects of Temperature-Dependent Viscosity on Forced Convection Inside a Porous Medium 总被引:1,自引:0,他引:1
Considering the exponential viscosity–temperature relation, effect of temperature-dependent viscosity on forced convection
of a liquid through a porous medium, bounded by isoflux parallel plates, is investigated numerically based on the general
model of momentum transfer. Local effects of viscosity variation on the distribution of velocity and temperature are analyzed.
Moreover, global aspects of the problem are investigated where corrections are proposed for total pressure drop and the fully
developed Nusselt number, in the form of out/in viscosity ratio. Results are obtained over a wide range of permeabilities
from clear (of solid material) fluid to very low permeability, where for constant properties one expects a nearly slug flow. 相似文献
18.
Adopting a two-temperature and two-velocity model, appropriate to a bidisperse porous medium (BDPM) proposed by Nield and
Kuznetsov (2008), the classical steady, mixed convection boundary layer flow about a horizontal, isothermal circular cylinder
embedded in a porous medium has been theoretically studied in this article. It is shown that the boundary layer analysis leads
to expressions for the flow and heat transfer characteristics in terms of an inter-phase momentum parameter, a thermal diffusivity
ratio, a thermal conductivity ratio, a permeability ratio, a modified thermal capacity ratio, and a buoyancy or mixed convection
parameter. The transformed partial differential equations governing the flow and heat transfer in the f-phase (the macro-pores)
and the p-phase (the remainder of the structure) are solved numerically using a very efficient implicit finite-difference
technique known as Keller-box method. A good agreement is observed between the present results and those known from the open
literature in the special case of a traditional Darcy formulation (monodisperse system). 相似文献
19.
Heat and Mass Transfer in MHD Micropolar Flow Over a Vertical Moving Porous Plate in a Porous Medium
Youn J. Kim 《Transport in Porous Media》2004,56(1):17-37
An analysis is presented for the problem of free convection with mass transfer flow for a micropolar fluid via a porous medium bounded by a semi-infinite vertical porous plate in the presence of a transverse magnetic field. The plate moves with constant velocity in the longitudinal direction, and the free stream velocity follows an exponentially small perturbation law. A uniform magnetic field acts perpendicularly to the porous surface in which absorbs the micropolar fluid with a suction velocity varying with time. Numerical results of velocity distribution of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. Also, the results of the skin-friction coefficient, the couple stress coefficient, the rate of the heat and mass transfers at the wall are prepared with various values of fluid properties and flow conditions. 相似文献
20.
The optimization of heat transfer for forced convection in a composite porous channel was studied. We investigated the question where should one place, in the core or in the sheath, the material with high permeability and high-thermal conductivity and where should one place the material with low permeability and low-thermal conductivity, to maximize heat transfer from the walls. We also investigated the optimal heat transfer situation when one has the freedom to vary the relative volumes of the core and the sheath. 相似文献