Effects of Mass Transfer and Free-Convection Currents on the Flow Near a Moving Vertical Plate With Ramped Wall Temperature

2009 ◽  
Author(s):  
M. Narahari ◽  
Binay K. Dutta
Keyword(s):  
Mass Transfer ◽  
Free Convection ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Buoyancy Force ◽  
Vertical Plate ◽  
Flow Temperature ◽  
Thermal Buoyancy ◽  
Laplace Transform Technique ◽  
Thermal Buoyancy Force

A theoretical analysis to the problem of free convection flow induced by an infinite moving vertical plate subject to a ramped surface temperature with simultaneous mass transfer to or from the surface is presented. The plate temperature increases linearly over a specified period of time until it reaches a constant value. Diffusional mass transfer occurs at the surface contributing to the density gradient in the boundary layer. An exact analytical solution to the governing equations for flow, temperature and concentration with coupled boundary conditions in the dimensionless form have been developed using the Laplace transform technique. Heat and mass transfer at the plate are assumed to be purely diffusive in nature. The cases of impulsive start and uniformly accelerating start of the plate are considered and solutions for the flow, temperature and concentration fields are derived. The effects of different system parameters have been studied in terms of relevant dimensionless groups such as Grashof number (Gr), Prandtl number (Pr), Schmidt number (Sc), time (t) and the mass to thermal buoyancy ratio (N). The possible cases of the last parameter, namely N = 0 (the buoyancy force is due to thermal diffusion only), N > 0 (the mass buoyancy force acts in the same direction of thermal buoyancy force) and N < 0 (the mass buoyancy force acts in the opposite direction of thermal buoyancy force) are investigated and their effects on the velocity field and skin-friction are explicitly determined. The ramped temperature boundary condition predictably has an enhancing effect on the skin friction. The mass flux to the plate influences the velocity and hence the skin friction. A critical analysis of the coupled heat and mass transfer phenomena is provided. The free convection near a ramped temperature plate has also been compared with the flow near a plate with constant temperature as a limiting case.

Combined Heat and Mass Transfer in Mixed Convection over a Horizontal Flat Plate

1980 ◽  
Vol 102 (3) ◽  
pp. 538-543 ◽  
Author(s):  
T. S. Chen ◽  
F. A. Strobel
Keyword(s):  
Mass Transfer ◽  
Flat Plate ◽  
Heat And Mass Transfer ◽  
Transfer Rate ◽  
Buoyancy Force ◽  
Schmidt Number ◽  
Thermal Buoyancy ◽  
Buoyancy Forces ◽  
Thermal Buoyancy Force ◽  
Species Diffusion

The combined effects of buoyancy forces from thermal and species diffusion on the heat and mass transfer characteristics are analyzed for laminar boundary layer flow over a horizontal flat plate. The analysis is restricted to processes with low concentration levels such that the interfacial velocities due to mass diffusion and the diffusion-thermo/thermo-diffusion effects can be neglected. Numerical results for friction factor, Nusselt number, and Sherwood number are presented for gases having a Prandtl number of 0.7, with Schmidt numbers ranging from 0.6 to 2.0. In general, it is found that, for the thermally assisting flow, the surface heat and mass transfer rates as well as the wall shear stress increase with increasing thermal buoyancy force. These quantities are further enhanced when the buoyancy force from species diffusion assists the thermal buoyancy force, but are reduced when the two buoyancy forces oppose each other. While a higher heat transfer rate is found to be associated with a lower Schmidt number, a higher mass transfer rate occurs at a higher Schmidt number.

Unsteady free convection flow past a periodically accelerated vertical plate with Newtonian heating

2016 ◽  
Vol 26 (7) ◽  
pp. 2119-2138 ◽  
Author(s):  
M.C. Raju ◽  
S.V.K. Varma ◽  
A.J. Chamkha
Keyword(s):  
Mass Transfer ◽  
Free Convection ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Convection Flow ◽  
Convection Boundary Layer ◽  
Physical Parameters ◽  
Content Type ◽  
Flow Past ◽  
Laplace Transform Technique

Purpose The purpose of this paper is to present an analytical study for a problem of unsteady free convection boundary layer flow past a periodically accelerated vertical plate with Newtonian heating (NH). Design/methodology/approach The equations governing the flow are studied in the closed form by using the Laplace transform technique. The effects of various physical parameters are studied through graphs and the expressions for skin friction, Nusselt number and Sherwood number are also derived and discussed numerically. Findings It is observed that velocity, concentration and skin friction decrease with the increasing values of Sc whereas temperature distribution decreases in the increase in Pr in the presence of NH. Research limitations/implications This study is limited to a Newtonian fluid. This can be extended for non-Newtonian fluids. Practical implications Heat and mass transfer frequently occurs in chemically processed industries, distribution of temperature and moisture over agricultural fields, dispersion of fog and environment pollution and polymer production. Social implications Free convection flow of coupled heat and mass transfer occurs due to the temperature and concentration differences in the fluid as a result of driving forces. For example, in atmospheric flows, thermal convection resulting from heating of the earth by sunlight is affected differences in water vapor concentration. Originality/value The authors have studied heat and mass transfer effects on unsteady free convection boundary layer flow past a periodically accelerated vertical surface with NH, where the heat transfer rate from the bounding surface with a finite heat capacity is proportional to the local surface temperature, and which is usually termed as conjugate convective flow. The equations governing the flow are studied in the closed form by using the Laplace transform technique. The effects of various physical parameters are studied through graphs and the expression for skin friction also derived and discussed.

Soret and Radiation Effects on Transient MHD Free Convection From an Impulsively Started Infinite Vertical Plate

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
N. Ahmed
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Free Convection ◽  
Thermal Radiation ◽  
Skin Friction ◽  
Vertical Plate ◽  
Soret Effect ◽  
Viscous Drag ◽  
Laplace Transform Technique ◽  
Infinite Vertical Plate

An exact solution to the problem of MHD transient free convection and mass transfer flow of a viscous, incompressible, and electrically conducting fluid past a suddenly started infinite vertical plate taking into account the thermal diffusion as well as the thermal radiation is presented. Assuming the medium to be nonscattered and the fluid to be nongray, emitting–absorbing, and optically thin radiation limit properties, the equations governing the flow and heat and mass transfer are solved by Laplace transform technique. The expressions for the velocity field, the concentration field, the skin friction at the plate in the direction of the flow, and the coefficient of heat transfer and mass transfer from the plate to the fluid have been obtained, and their numerical values for different values of the physical parameters involved in the problem have been demonstrated in graphs and tables, and these are physically interpreted. It is found that the thermal radiation retards the fluid flow whereas the Soret effect accelerates the flow. The viscous drag on the plate is increased under the Soret and magnetic field effects whereas the thermal radiation reduces the skin friction. Further, the rate of heat transfer at the plate increases under thermal radiation effect. Also, in the presence of radiation, the Soret effect results in a steady increase in the mass flux from the fluid to the plate.

Numerical Analysis of Interaction Between Inertial and Thermosolutal Buoyancy Forces on Convective Heat Transfer in a Lid-Driven Cavity

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
D. Senthil kumar ◽  
K. Murugesan ◽  
Akhilesh Gupta
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Buoyancy Force ◽  
Inertial Force ◽  
Driven Cavity ◽  
Thermal Buoyancy ◽  
Buoyancy Forces ◽  
Thermal Buoyancy Force

In this paper, results on double diffusive mixed convection in a lid-driven cavity are discussed in detail with a focus on the effect of interaction between fluid inertial force and thermosolutal buoyancy forces on convective heat and mass transfer. The governing equations for the mathematical model of the problem consist of vorticity transport equation, velocity Poisson equations, energy equation and solutal concentration equation. Numerical solution for the field variables are obtained by solving the governing equations using Galerkin’s weighted residual finite element method. The interaction effects on convective heat and mass transfer are analyzed by simultaneously varying the characteristic parameters, 0.1<Ri<5, 100<Re<1000, and buoyancy ratio (N), −10<N<10. In the presence of strong thermosolutal buoyancy forces, the increase in fluid inertial force does not make significant change in convective heat and mass transfer when the thermal buoyancy force is smaller than the fluid inertial force. The fluid inertial force enhances the heat and mass transfer only when the thermal buoyancy force is either of the same magnitude or greater than that of the fluid inertial force. The presence of aiding solutal buoyancy force enhances convective heat transfer only when Ri becomes greater than unity but at higher buoyancy ratios, the rate of increase in heat transfer decreases for Re=400 and increases for Re=800. No significant change in heat transfer is observed due to aiding solutal buoyancy force for Ri≤1 irrespective of the Reynolds number.

MHD Natural Convection Heat and Mass Transfer Flow Past a Time Dependent Moving Vertical Plate with Ramped Temperature in a Rotating Medium with Hall Effects, Radiation and Chemical Reaction

2014 ◽  
Vol 31 (1) ◽  
pp. 91-104 ◽  
Author(s):  
G. S. Seth ◽  
S. Sarkar
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Chemical Reaction ◽  
Vertical Plate ◽  
Convection Heat ◽  
Flow Past ◽  
Hall Effects ◽  
Transfer Flow

AbstractAn investigation of unsteady hydromagnetic natural convection heat and mass transfer flow of an electrically conducting, viscous, incompressible and optically thick radiating fluid past an impulsively moving infinite vertical plate embedded in a uniform porous medium in a rotating system with Hall effects in the presence of homogeneous first order chemical reaction is carried out when temperature of the plate has a temporarily ramped profile. Exact solution of the governing equations is obtained in closed form by Laplace transform technique. Expressions for skin friction due to primary and secondary flows and Nusselt number are derived for both ramped temperature and isothermal plates. Expression for Sherwood number is also derived. The numerical values of primary and secondary fluid velocities, fluid temperature and species concentration are displayed graphically whereas those of skin friction are presented in tabular form for various values of pertinent flow parameters. In order to highlight the influence of ramped temperature distribution within the plate on the flow-field, the fluid flow past a ramped temperature plate is compared with the one past an isothermal plate.

scholarly journals An Exact Analysis of Heat and Mass Transfer Past a Vertical Plate with Newtonian Heating

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Abid Hussanan ◽  
Ilyas Khan ◽  
Sharidan Shafie
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Nusselt Number ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Vertical Plate ◽  
Newtonian Heating ◽  
Governing Equations ◽  
Exact Analysis ◽  
Temperature Distributions

An exact analysis of heat and mass transfer past an oscillating vertical plate with Newtonian heating is presented. Equations are modelled and solved for velocity, temperature, and concentration using Laplace transforms. The obtained solutions satisfy governing equations and conditions. Expressions of skin friction, Nusselt number, and Sherwood number are obtained and presented in tabular forms. The results show that increasing the Newtonian heating parameter leads to increase velocity and temperature distributions whereas skin friction decreases and rate of heat transfer increases.

scholarly journals Heat and Mass Transfer of Unsteady Hydromagnetic Free Convection Flow Through Porous Medium Past a Vertical Plate with Uniform Surface Heat Flux

2017 ◽  
Vol 47 (3) ◽  
pp. 25-58 ◽  
Author(s):  
Mohamed Abd El-Aziz ◽  
Aishah S. Yahya
Keyword(s):  
Mass Transfer ◽  
Heat Flux ◽  
Porous Medium ◽  
Free Convection ◽  
Heat And Mass Transfer ◽  
Transport Model ◽  
Convection Flow ◽  
Physical Parameters ◽  
Free Convection Flow ◽  
Laplace Transform Technique

AbstractSimultaneous effects of thermal and concentration diffusions in unsteady magnetohydrodynamic free convection flow past a moving plate maintained at constant heat flux and embedded in a viscous fluid saturated porous medium is presented. The transport model employed includes the effects of thermal radiation, heat sink, Soret and chemical reaction. The fluid is considered as a gray absorbing-emitting but non-scattering medium and the Rosseland approximation in the energy equations is used to describe the radiative heat flux for optically thick fluid. The dimensionless coupled linear partial differential equations are solved by using Laplace transform technique. Numerical results for the velocity, temperature, concentration as well as the skin friction coefficient and the rates of heat and mass transfer are shown graphically for different values of physical parameters involved.

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