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1.
The problem of steady, laminar, simultaneous heat and mass transfer by natural convection flow over a vertical permeable plate embedded in a uniform porous medium in the presence of inertia and thermal dispersion effects is investigated for the case of linear variations of both the wall temperature and concentration with the distance along the plate. Appropriate transformations are employed to transform the governing differential equations to a non-similar form. The transformed equations are solved numerically by an efficient implicit, iterative, finite-difference scheme. The obtained results are checked against previously published work on special cases of the problem and are found to be in good agreement. A parametric study illustrating the influence of the porous medium effects, heat generation or absorption, wall suction or injection, concentration to thermal buoyancy ratio, thermal dispersion parameter, and the Schmidt number on the fluid velocity, temperature and concentration as well as the skin-friction coefficient and the Nusselt and Sherwood numbers is conducted. The results of this parametric study are shown graphically and the physical aspects of the problem are highlighted and discussed. 相似文献
2.
This work is focused on the numerical modeling of steady, laminar, heat and mass transfer by MHD mixed convection from a semi-infinite,
isothermal, vertical and permeable surface immersed in a uniform porous medium in the presence of thermal radiation and Dufour
and Soret effects. A mixed convection parameter for the entire range of free-forced-mixed convection is employed and the governing
equations are transformed into non-similar equations. These equations are solved numerically by an efficient, implicit, iterative,
finite-difference scheme. The obtained results are checked against previously published work on special cases of the problem
and are found to be in excellent agreement. A parametric study illustrating the influence of the thermal radiation coefficient,
magnetic field, porous medium inertia parameter, concentration to thermal buoyancy ratio, and the Dufour and Soret numbers
on the fluid velocity, temperature and concentration as well as the local Nusselt and the Sherwood numbers is conducted. The
obtained results are shown graphically and the physical aspects of the problem are discussed. 相似文献
3.
The problem of combined heat and mass transfer by natural convection over a permeable cone embedded in a uniform porous medium
in the presence of an external magnetic field and internal heat generation or absorption effects is formulated. The cone surface
is maintained at either constant temperature and constant concentration or uniform heat and mass fluxes. In addition, the
cone surface is assumed permeable in order to allow for possible fluid wall suction or blowing. The resulting governing equations
are non-dimensionalized and transformed into a non-similar form and then solved numerically by an implicit, iterative, finite-difference
method. Comparisons with previously published work are performed and excellent agreement between the results is obtained.
A parametric study of the physical parameters is conducted and a representative set of numerical results for the temperature
and concentration profiles as well as the local Nusselt number and the Sherwood number is illustrated graphically to show
special trends of the solutions.
Received on 5 June 2000 / Published online: 29 November 2001 相似文献
4.
Irfan Anjum Badruddin N. J. Salman Ahmed Abdullah A. A. A. Al-Rashed Jeevan Kanesan Sarfaraz Kamangar H. M. T. Khaleed 《Transport in Porous Media》2012,91(2):697-715
The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous
medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing
partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium
is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near
the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding
and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number,
aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented. 相似文献
5.
Ibrahim A. Abbas M.F. El-Amin Amgad Salama 《International Journal of Heat and Fluid Flow》2009,30(2):229-236
The present article considers a numerical study of thermal dispersion effect on the non-Darcy natural convection over a vertical flat plate in a fluid saturated porous medium. Forchheimer extension is considered in the flow equations. 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 non-dimensional governing equations are solved by the finite element method (FEM) with a Newton–Raphson solver. Numerical results for the details of the stream function, velocity and temperature contours and profiles as well as heat transfer rates in terms of Nusselt number are obtained. The study shows that the increase in thermal dispersion coefficient of the porous medium results in more heat energy to disperse away in the normal direction to the wall. This induces more fluid to flow along the wall, enhancing the heat transfer coefficient particularly near the wall. 相似文献
6.
The effects of Joule-heating, chemical reaction and thermal radiation on unsteady MHD natural convection from a heated vertical
porous plate in a micropolar fluid are analyzed. The partial differential equations governing the flow and heat and mass transfer
have been solved numerically using an implicit finite-difference scheme. The case corresponding to vanishing of the anti-symmetric
part of the stress tensor that represents weak concentrations is considered. The numerical results are validated by favorable
comparisons with previously published results. A parametric study of the governing parameters, namely the magnetic field parameter,
suction/injection parameter, radiation parameter, chemical reaction parameter, vortex viscosity parameter and the Eckert number
on the linear velocity, angular velocity, temperature and the concentration profiles as well as the skin friction coefficient,
wall couple stress coefficient, Nusselt number and the Sherwood number is conducted. A selected set of numerical results is
presented graphically and discussed. 相似文献
7.
The present paper is concerned with the study of radiation effects on the combined (forced-free) convection flow of an optically
dense viscous incompressible fluid over a vertical surface embedded in a fluid saturated porous medium of variable porosity
with heat generation or absorption. The effects of radiation heat transfer from a porous wall on convection flow are very
important in high temperature processes. The inclusion of radiation effects in the energy equation leads to a highly non-linear
partial differential equations which are transformed to a system of ordinary differential equations using non-similarity transformation.
These equations are then solved numerically using implicit finite-difference method subject to appropriate boundary and matching
conditions. A parametric study of the physical parameters such as the particle diameter-based Reynolds number, the flow based
Reynolds number, the Grashof number, the heat generation or absorption co-efficient and radiation parameter is conducted on
temperature distribution. The effects of radiation and other physical parameters on the local skin friction and on local Nusselt
number are shown graphically. It is interesting to observe that the momentum and thermal boundary layer thickness increases
with the radiation and decrease with increase in the Prandtl number. 相似文献
8.
A theoretical study is performed on heat and fluid flow in partially porous medium filled parallel plate channel. A uniform symmetrical heat flux is imposed onto the boundaries of the channel partially filled with porous medium. The dimensional forms of the governing equations are solved numerically for different permeability and effective thermal conductivity ratios. Then, the governing equations are made dimensionless and solved analytically. The results of two approaches are compared and an excellent agreement is observed, indicating correctness of the both solutions. An overall Nusselt number is defined based on overall thermal conductivity and difference between the average temperature of walls and mean temperature to compare heat transfer in different channels with different porous layer thickness, Darcy number, and thermal conductivity ratio. Moreover, individual Nusselt numbers for upper and lower walls are also defined and obtained. The obtained results show that the maximum overall Nusselt number is achieved for thermal conductivity ratio of 1. At specific values of Darcy number and thermal conductivity ratio, individual Nusselt numbers approach to infinity since the value of wall temperatures approaches to mean temperature. 相似文献
9.
Amgad Salama M. F. El-Amin Ibrahim Abbas Shuyu Sun 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(12):1865-1876
The problem of viscous dissipation and thermal dispersion in saturated porous medium is numerically investigated for the case
of non-Darcy flow regime. The fluid is induced to flow upward by natural convection as a result of a semi-infinite vertical
wall that is immersed in the porous medium and is kept at constant higher temperature. The boundary layer approximations were
used to simplify the set of the governing, nonlinear partial differential equations, which were then non-dimensionalized and
solved using the finite elements method. The results for the details of the governing parameters are presented and investigated.
It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity
of the moving fluid (i.e., viscous dissipation) resulted in insignificant generation of heat for the range of parameters considered
in this study. On the other hand, thermal dispersion has shown to disperse heat energy normal to the wall more effectively
compared with the normal diffusion mechanism. 相似文献
10.
The steady natural convection flow on a horizontal cone embedded in a saturated porous medium with non-uniform wall temperature/concentration
or heat/mass flux and suction/injection has been investigated. Non-similar solutions have been obtained. The nonlinear coupled
differential equations under boundary layer approximations governing the flow have been numerically solved. The Nusselt and
Sherwood numbers are found to depend on the buoyancy forces, suction/injection rates, variation of wall temperature/concentration
or heat/mass flux, Lewis number and the non-Darcy parameter. 相似文献
11.
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
12.
Faiza A.Salama 《Acta Mechanica Sinica》2011,27(4):531-540
A boundary layer analysis is presented to investigate numerically the effects of radiation,thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a flat surface in a porous medium.The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and they are solved numerically by using the fourth order Runge-Kutta method with shooting technique for some values of physical parameters.Comparisons with previously published work are performed and the results are found to be in very good agreement.Many results are obtained and a representative set is displayed graphically to illustrate the influence of the various parameters on the dimensionless velocity,temperature and concentration profiles as well as the local skin-friction coefficient,wall heat transfer,particle deposition rate and wall thermophoretic deposition velocity.The results show that the magnetic field induces acceleration of the flow,rather than deceleration(as in classical magnetohydrodynamics(MHD) boundary layer flow) but to reduce temperature and increase concentration of particles in boundary layer.Also,there is a strong dependency of the concentration in the boundary layer on both the Schmidt number and mass transfer parameter. 相似文献
13.
This paper reports a detailed numerical investigation on mixed convection flow of a polar fluid through a porous medium due
to the combined effects of thermal and mass diffusion. The energy equation accounts for heat generation or absorption, while
the nth order homogeneous chemical reaction between the fluid and the diffusing species is included in the mass diffusion equation.
The governing equations of the linear momentum, angular momentum, energy and concentration are obtained in a non-similar form
by introducing a suitable group of transformations. The final set of non-similar coupled non-linear partial differential equations
is solved using an implicit finite-difference scheme in combination with quasi-linearization technique. The effects of various
parameters on the velocity, angular velocity, temperature and concentration fields are investigated. Numerical results for
the skin friction coefficient, wall stress of angular velocity, Nusselt number and Sherwood number are also presented. 相似文献
14.
An analysis is presented to investigate the effects of thermophoresis and variable viscosity on MHD mixed convective heat
and mass transfer of a viscous, incompressible and electrically conducting fluid past a porous wedge in the presence of chemical
reaction. The wall of the wedge is embedded in a uniform porous medium in order to allow for possible fluid wall suction or
injection. The governing boundary layer equations are written into a dimensionless form by similarity transformations. The
transformed coupled nonlinear ordinary differential equations are solved numerically by using the R.K. Gill and shooting methods.
Favorable comparison with previously published work is performed. Numerical results for the dimensionless velocity, temperature
and concentration profiles as well as for the skin friction, heat and mass transfer and deposition rate are obtained and displayed
graphically for pertinent parameters to show interesting aspects of the solution. 相似文献
15.
《International Journal of Heat and Fluid Flow》1987,8(2):93-101
A theoretical study of conjugate natural convection and film condensation in porous media is reported. The natural convection phenomenon takes place along one side of a vertical impermeable wall and the condensation phenomenon along the other side. This wall constitutes the interface between two spaces filled with fluid-saturated porous media. The flow in both porous spaces is modelled on the basis of the Brinkman-modified Darcy momentum equation which satisfies the condition of zero velocity on a solid boundary. The temperature and flow fields in the porous medium are completely determined in the natural convection side as well as in the condensation side of the wall. In addition, the dependence of the wall heat flux and temperature distributions on height and on a number of dimensionless groups relevant to the problem is thoroughly documented. Important results pertinent to the impact of the problem parameters on the overall heat leak from the condensation space to the natural convection space are also reported. These results are presented with the help of the Nusselt number. Finally, the effect of the wall thermal resistance on the heat and fluid flow characteristics of the system is determined. 相似文献
16.
This work presents a similarity solution for boundary layer flow through a porous medium over a stretching porous wall. Two
considered wall boundary conditions are power-law distribution of either wall temperature or heat flux which are general enough
to cover the isothermal and isoflux cases. In addition to momentum, both first and second laws of thermodynamics analyses
of the problem are investigated. Independent numerical simulations are also performed for verification of the proposed analytical
solution. The results, from the two independent approaches, are found to be in complete agreement. A comprehensive parametric
study is presented and it is shown that heat transfer and entropy generation rates increase with Reynolds number, Prandtl
number, and suction to the surface. 相似文献
17.
Thermal radiation, thermal diffusion, and diffusion-thermo effects on heat and mass transfer by mixed convection of non-Newtonian power-law fluids over a vertical permeable surface embedded in a saturated porous medium are investigated. The governing equations describing the problem are non-dimensionalized and transformed into a non-similar form. The transformed equations are solved by using the local non-similarity method combined with the shooting technique. The effects of the physical parameters of the problem on the fluid temperature and concentration are illustrated graphically and analyzed. Also, the effects of the pertinent parameters on the local Nusselt number and the local Sherwood number are presented. 相似文献
18.
This paper studies mixed convection, double dispersion and chemical reaction effects on heat and mass transfer in a non-Darcy non-Newtonian fluid over a vertical surface in a porous medium under the constant temperature and concentration. The governing boundary layer equations, namely, momentum, energy and concentration, are converted to ordinary differential equations by introducing similarity variables and then are solved numerically by means of fourth-order Runge-Kutta method coupled with double-shooting technique. The velocity, temperature concentration, heat and mass transfer profiles are presented graphically for various values of the parameters, and the influence of viscosity index n, thermal and solute dispersion, chemical reaction parameter χ are observed. 相似文献
19.
The present study is devoted to investigate the influences of mass transfer on buoyancy induced flow over vertical flat plate
embedded in a non-Newtonian fluid saturated porous medium. The Ostwald–de Waele power-law model is used to characterize the
non-Newtonian fluid behavior. Similarity solution for the transformed governing equations is obtained with prescribed variable
surface heat flux. Numerical results for the details of the velocity, temperature and concentration profiles are shown on
graphs. Excess surface temperature as well as concentration gradient at the wall associated with heat flux distributions,
which are entered in tables, have been presented for different values of the power-law index n, buoyancy ration B and the exponent λ as well as Lewis number Le.
Received on 26 April 2000 相似文献
20.
Analytical and numerical analyses have been performed for fully developed forced convection in a fluid-saturated porous medium channel bounded by two parallel plates. The channel walls are assumed to be finite in thickness. Conduction heat transfer inside the channel wall is also accounted and the full problem is treated as a conjugate heat transfer problem. The flow in the porous material is described by the Darcy–Brinkman momentum equation. The outer surfaces of the solid walls are treated as isothermal. A temperature dependent volumetric heat generation is considered inside the solid wall only. Analytical expressions for velocity, temperature, and Nusselt number are obtained after simplifying and solving the governing differential equations with reasonable approximations. Subsequent results obtained by numerical calculations show an excellent agreement with the analytical results. 相似文献