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1.
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
2.
In this paper we present a mathematical analysis of heat and mass transfer phenomena in a visco–elastic fluid flow over an
accelerating stretching sheet in the presence of heat source/sink, viscous dissipation and suction/blowing. Similarity transformations
are used to convert highly non-linear partial differential equations into ordinary differential equations. Several closed
form analytical solutions for non-dimensional temperature, concentration, heat flux, mass flux profiles are obtained in the
form of confluent hypergeometric (Kummer's) functions for two different cases of the boundary conditions, namely, (i) wall
with prescribed second order power law temperature and second order power law concentration (PST), and (ii) wall with prescribed
second order power law heat flux and second order power law mass flux (PHF). The effect of various physical parameters like
visco–elasticity, Eckert number, Prandtl number, heat source/sink, Schmidt number and suction/blowing parameter on temperature
and concentration profiles are analysed. The effects of all these parameters on wall temperature gradient and wall concentration
gradient are also discussed.
Received on 23 March 2000 / Published online: 29 November 2001 相似文献
3.
A two-dimensional numerical simulation of natural convection in a rectangular enclosure heated from below and cooled from
above has been conducted with non-Newtonian phase-change-material (PCM) microcapsulate slurry with latent heat capacities.
The formulation of the mathematical model in dimensionless co-ordinates and discretization of the governing equations have
been done using the finite volume method. Both natural convection and heat transfer characteristics are discussed about natural
convection with PCM microcapsulate slurry, which exhibits the pseudoplastic non-Newtonian fluid behavior and a peak value
in the specific heat capacity with latent heat. The viscosity of the present PCM microcapsulate slurry is assumed to follow
the Ostwald-de Waele power law fluid model with the power-law index n and the consistency coefficient K. The effects of phase-change material, the mass concentration, and the aspect ratio Ar on the natural convection heat transfer
are described, respectively. By comparing with the results of microcapsule slurry without phase change, the enhancement in
heat transfer is found in microcapsule slurry with phase change during the phase change temperature range. Numerical simulations
are performed in the following parametric ranges: the width–height aspect ratio of the enclosure Ar from 2 to 20, the mass
concentrations C
m of the slurry from 10 to 40%, power law index n of the slurry from 0.89 to 1.0 and Rayleigh numbers Ra ranges from 103 to 107. 相似文献
4.
Summary The effect of surface mass flux on the non-Darcy natural convection over a horizontal flat plate in a saturated porous medium
is studied using similarity solution technique. Forchheimer extension is considered in the flow equations. The suction/injection
velocity distribution has been assumed to have power function form Bx
l
, similar to that of the wall temperature distribution Ax
n
, where x is the distance from the leading edge. The thermal diffusivity coefficient has been assumed to be the sum of the molecular
diffusivity and the dynamic diffusivity due to mechanical dispersion. The dynamic diffusivity is assumed to vary linearly
with the velocity component in the x direction, i.e. along the hot wall. For the problem of constant heat flux from the surface (n=1/2), similarity solution is possible when the exponent l takes the value −1/2. Results indicate that the boundary layer thickness decreases whereas the heat transfer rate increases
as the mass flux parameter passes from the injection domain to the suction domain. The increase in the thermal dispersion
parameter is observed to favor the heat transfer by reducing the boundary layer thickness. The combined effect of thermal
dispersion and fluid suction/injection on the heat transfer rate is discussed.
Received 7 December 1995; accepted for publication 7 January 1997 相似文献
5.
P. Payvar 《Applied Scientific Research》1973,27(1):297-306
General expressions for fully developed temperature profiles and Nusselt numbers are obtained for heat transfer to non-Newtonian fluid flow between parallel plates and through circular pipes subjected to a uniform wall heat flux. The effect of viscous dissipation is taken into account since it may often be significant in the flow of non-Newtonian fluids. Asymptotic Nusselt numbers for three widely used models, i.e. the power law fluid, the Bingham plastic, and the Ellis fluid are obtained as specific results. 相似文献
6.
The method of similarity solution is used to study the influence of lateral mass flux and thermal dispersion on non-Darcy
natural convection over a vertical flat plate in a fluid saturated porous medium. Forchheimer extension is considered in the
flow equations and 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 suction/injection velocity distribution has been assumed
to have power function form Ax
l
, where x is the distance from the leading edge and the wall temperature distribution is assumed to be uniform. When l=−1/2, similarity solution is possible, and the results indicate that the boundary layer thickness decreases where as the
heat transfer rate increases as the mass flux parameter passes from injection domain to the suction domain. The increase in
the thermal dispersion parameter is observed to enhance the heat transfer. The combined effect of thermal dispersion and fluid
suction/injection on the heat transfer rate is discussed.
Received on 9 September 1996 相似文献
7.
This paper investigates the unsteady stagnation-point flow and heat transfer over a moving plate with mass transfer,which is also an exact solution to the unsteady Navier-Stokes(NS)equations.The boundary layer energy equation is solved with the closed form solutions for prescribed wall temperature and prescribed wall heat flux conditions.The wall temperature and heat flux have power dependence on both time and spatial distance.The solution domain,the velocity distribution,the flow field,and the temperature distribution in the fluids are studied for different controlling parameters.These parameters include the Prandtl number,the mass transfer parameter at the wall,the wall moving parameter,the time power index,and the spatial power index.It is found that two solution branches exist for certain combinations of the controlling parameters for the flow and heat transfer problems.The heat transfer solutions are given by the confluent hypergeometric function of the first kind,which can be simplified into the incomplete gamma functions for special conditions.The wall heat flux and temperature profiles show very complicated variation behaviors.The wall heat flux can have multiple poles under certain given controlling parameters,and the temperature can have significant oscillations with overshoot and negative values in the boundary layers.The relationship between the number of poles in the wall heat flux and the number of zero-crossing points is identified.The difference in the results of the prescribed wall temperature case and the prescribed wall heat flux case is analyzed.Results given in this paper provide a rare closed form analytical solution to the entire unsteady NS equations,which can be used as a benchmark problem for numerical code validation. 相似文献
8.
M. K. PARTHA 《应用数学和力学(英文版)》2010,31(5):565-574
In this paper, the natural convection in a non-Darcy porous medium is studied using a temperature-concentration-dependent density relation. The effect of the two parameters responsible for the nonlinear convection is analyzed for different values of the inertial parameter, dispersion parameters, Rayleigh number, Lewis number, Soret number, and Dufour number. In the aiding buoyancy, the tangential velocity increases steeply with an increase in the nonlinear temperature parameter and the nonlinear concentration parameter when the inertial effect is zero. However, when the inertial effect is non-zero, the effect of the nonlinear temperature parameter and the nonlinear concentration parameter on the tangential velocity is marginal. The concentration distribution varies appreciably and spreads in different ranges for different values of the double dispersion parameters, the inertial effect parameter, and also for the parameters which control the nonlinear temperature and the nonlinear concentration. Heat and mass transfer varies extensively with an increase in the nonlinear temperature parameter and the nonlinear concentration parameter depending on Dacry and non-Darcy porous media. The variation in heat and mass transfer when all the effects, i.e., the inertial effect, double dispersion ef- fects, and Soret and Dufour effects, are simultaneously zero and non-zero. The combined effects of the nonlinear temperature parameter, the nonlinear concentration parameter and buoyancy are analyzed. The effect of the nonlinear temperature parameter and the nonlinear concentration parameter and also the cross diffusion effects on heat and mass transfer are observed to be more in Darcy porous media compared with those in non- Darcy porous media. In the opposing buoyancy, the effect of the temperature parameter is to increase the heat and mass transfer rate, whereas that of the concentration parameter is to decrease. 相似文献
9.
Effects of Chemical Reaction and Double Dispersion on Non-Darcy Free Convection Heat and Mass Transfer 总被引:1,自引:0,他引:1
In this article, the effects of chemical reaction and double dispersion on non-Darcy free convection heat and mass transfer
from semi-infinite, impermeable vertical wall in a fluid saturated porous medium are investigated. The Forchheimer extension
(non-Darcy term) is considered in the flow equations, while the chemical reaction power–law term is considered in the concentration
equation. The first order chemical reaction (n = 1) was used as an example of calculations. The Darcy and non-Darcy flow, temperature and concentration fields in this study
are observed to be governed by complex interactions among dispersion and natural convection mechanisms. The governing set
of partial differential equations were non-dimensionalized and reduced to a set of ordinary differential equations for which
Runge–Kutta-based numerical technique were implemented. Numerical results for the detail of the velocity, temperature, and
concentration profiles as well as heat transfer rates (Nusselt number) and mass transfer rates (Sherwood number) are presented
in graphs. 相似文献
10.
The effect of chemical reaction on free convection heat and mass transfer for a non-Newtonian power law fluid over a vertical flat plate embedded in a fluid-saturated porous medium has been studied in the presence of the yield stress and the Soret effect. The governing boundary layer equations and boundary conditions are cast into a dimen- sionless form by similarity transformations, and the resulting system of equations is solved by a finite difference method. The results are preSented and discussed for concentration profiles, as well as the Nusselt number and the Sherwood number for various values of the parameters, which govern the problem. The results obtained show that the flow field is influenced appreciably by the presence of the chemical reaction parameter γ the order of.the chemical reaction parameter m, the Soret number St, the buoyancy ratio N, the Lewis number Le, and the dimensionless rheological parameter Ω. 相似文献
11.
Numerical analysis of the free convection coupled heat and mass transfer is presented for non-Newtonian power-law fluids with the yield stress flowing over a two-dimensional or axisymmetric body of an arbitrary shape in a fluid-saturated porous medium. The governing boundary layer equations and boundary conditions are cast into a dimensionless form by the similarity transformation. The resulting system of equations is solved by a finite difference method. The parameters studied are the rheological constants, the buoyancy ratio, and the Lewis number. Representative velocity, temperature, and concentration profiles are presented and discussed. It is found that the results depend strongly on the values of the yield stress parameter and the power-law index of the non-Newtonian fluid. 相似文献
12.
Numerical analysis of the free convection coupled heat and mass transfer is presented for non-Newtonian power-law fluids with
the yield stress flowing over a two-dimensional or axisymmetric body of an arbitrary shape in a fluid-saturated porous medium.
The governing boundary layer equations and boundary conditions are cast into a dimensionless form by the similarity transformation.
The resulting system of equations is solved by a finite difference method. The parameters studied are the rheological constants,
the buoyancy ratio, and the Lewis number. Representative velocity, temperature, and concentration profiles are presented and
discussed. It is found that the results depend strongly on the values of the yield stress parameter and the power-law index
of the non-Newtonian fluid. 相似文献
13.
The effect of lateral mass flux on mixed convection heat and mass transfer in a saturated porous medium adjacent to an inclined
permeable surface is analyzed. A similarity solution is obtained when surface temperature and concentration, free stream velocity
and injection/suction velocity of fluid are prescribed as power functions of distance from the leading edge. The cases when
the flow and buoyancy forces are in the same and opposite directions are discussed both for aiding and opposing buoyancy effects.
The governing parameters are the mixed convection parameter Gr, the Lewis number Le, the buoyancy ratio N, the lateral mass flux parameter f
w, representing the effects of injection or withdrawal of fluid at the wall, and λ which specifies three cases of the inclined
plate. The interactive effect of these parameters on heat and mass transfer rates are presented. It is observed that the diffusion
ratio (Le) has a more pronounced effect on concentration field than on flow and temperature fields. It is found that the rates
of heat and mass transfer increase with suction and decrease with injection of the fluid.
Received on 31 August 2000 / Published online: 29 November 2001 相似文献
14.
A. A. Mohammadein 《Meccanica》2010,45(1):89-96
An analysis of free convection heat transfer in electrically conducting power law non-Newtonian fluid over a thin axisymmetric
body of constant temperature is carried out. The uniform external magnetic field acts normally to the surface through the
induced boundary layer. In view of the fact that most of the non-Newtonian fluids have large Prandtl number, the momentum
equation is simplified. The equations of conservation of mass, momentum and energy which govern and describe the flow and
heat transfer are solved numerically. The effect of the magnetic field on the velocity, temperature, the coefficient of friction
and the Nusselt number are investigated. Numerical results are tabulated, presented graphically and discussed. 相似文献
15.
The problem of natural convective heat transfer for a non-Newtonian fluid from an impermeable vertical plate embedded in a fluid-saturated porous medium has been analyzed. Non-Darcian, radiative and thermal dispersion effects have been considered in the present analysis. The governing boundary layer equations and boundary conditions are cast into a dimensionless form and simplified by using a similarity transformation. The resulting system of equations is solved by using a double shooting Runge–Kutta method. The effect of viscosity index n, the conduction–radiation parameter R, the non-Darcy parameter Gr*, the thermal dispersion parameter Ds and the suction/injection parameter fw on the fluid velocities, temperatures and the local Nusselt number are discussed. 相似文献
16.
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
17.
Muhammet Yürüsoy Hüseyin Bayrakçeken Mehmet Kapucu Fatih Aksoy 《International Journal of Non》2008,43(7):588-599
The steady-state flow of a third grade fluid between concentric circular cylinders is considered and entropy generation due to fluid friction and heat transfer in the annular pipe is examined. Depending upon the fluid viscosity, entropy generation in the flow system varies. The third grade fluid is employed to account for the non-Newtonian effect while Vogel model is accommodated for temperature-dependent viscosity. The analysis is based on perturbation technique. The closed form solutions for velocity, temperature and entropy fields are presented. Entropy generation due to fluid friction and heat transfer in the flow system is formulated. The influence of viscosity parameters A and B on the entropy generation number is investigated. It is found that entropy generation number reduces with increasing viscosity parameter A, which is more pronounced in the region close to the annular pipe inner wall and opposite is true for increasing viscosity parameter B. 相似文献
18.
Heat transfer characteristics of a non-Newtonian fluid on a power-law stretched surface of variable temperature with suction
or injection were investigated. Similarity solutions of the laminar boundary layer equations describing heat transfer and
fluid flow in a quiescent fluid were obtained and solved numerically. Velocity and temperature profiles as well as the Nusselt
number, Nu, were studied for two thermal boundary conditions; uniform surface temperature and variable surface temperature,
for different parameters; Prandtl number Pr, temperature exponent b, velocity exponent m, injection parameter d and power-law index n. It was found that decreasing injection parameter d, and power-law index n and increasing Prandtl number Pr and surface temperature exponent b enhance the heat transfer coefficient.
Received on 27 April 2000 相似文献
19.
A periodic transient test technique based on the axial dispersion model is proposed for the determination of both heat transfer coefficients and axial dispersion coefficients in heat exchangers. The model uses a parameter called the axial dispersive Peclet number to account for the deviation of the flow pattern from ideal plug flow. It takes both axial dispersion in the fluid and axial heat conduction in the wall into account and is solved analytically by means of a complex Fourier transform. Experiments conducted on dented copper tubes show that axial dispersion has a significant effect on the dynamic temperature response of a heat exchanger. 相似文献
20.
M. K. Partha 《Heat and Mass Transfer》2008,44(8):969-977
Thermophoresis particle deposition in free convection on a vertical plate embedded in a fluid saturated non-Darcy porous medium
is studied using similarity solution technique. The effect of Soret and Dufour parameters on concentration distribution, wall
thermophoretic deposition velocity, heat transfer and mass transfer is discussed in detail for different values of dispersion
parameters (Ra
γ, Ra
ξ) inertial parameter F and Lewis number Le. The result indicates that the Soret effect is more influential in increasing the concentration distribution in both aiding
as well as opposing buoyancies. Also, the non-dimensional heat transfer coefficient and non-dimensional mass transfer coefficient
changes according to different values of thermophoretic coefficient k. 相似文献