Steady MHD Heat Research Articles

Thermal radiation and viscous dissipation effects on steady MHD heat and mass transfer flow of a micropolar fluid over an inclined isothermal permeable surface in the presence of thermophoresis

Thermal radiation and viscous dissipation effects on steady MHD heat and mass transfer flow of a micropolar fluid over an inclined isothermal permeable surface in the presence of thermophoresis

Steady MHD Heat and Mass Transfer Flow Over a Permeable Stretching Surface with Velocity, Thermal, and Mass Slip Conditions

Steady MHD Heat and Mass Transfer Flow Over a Permeable Stretching Surface with Velocity, Thermal, and Mass Slip Conditions

Hall Effects on Steady MHD Heat and Mass Transfer Free Convection Flow along an Inclined Stretching Sheet with Suction and Heat Generation

The heat and mass transfer of a steady flow of an incompressible electrically conducting fluid over an inclined stretching plate under the influence of an applied uniform magnetic field with heat generation and suction and the effects of Hall current are investigated. Using suitable similarity transformations the governing boundary layer equations for momentum, thermal energy and concentration are reduced to a set of coupled ordinary differential equations which are then solved numerically by the shooting method along with Runge- Kutta fourth-fifth order integration scheme. The numerical results concerned with the velocity, secondary velocity, temperature and concentration profiles effects of various parameters on the flow fields are investigated and presented graphically. The results have possible technological applications in liquid-based systems involving stretchable materials. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i3.16903 J. Sci. Res. 6 (3), 457-466 (2014)

Comments on the paper “A study of induced magnetic field with chemically reacting and radiating fluid past a vertical permeable plate” by S. Ahmed

In the paper "A study of induced magnetic field with chemically reacting and radiating fluid past a vertical permeable plate" by S. Ahmed published in Journal of Engineering Physics and Thermophysics [1], the influence of thermal radiation and chemical reaction on the steady MHD heat and mass transfer by a mixed convective flow of a viscous, incompressible, electrically conducting Newtonian fluid past a vertical permeable plate with account for an induced magnetic field was investigated. The similarity solutions of the transformed nondimensional governing equations were obtained by the series expansion technique. All the results were presented for air and water at 20C with the Prandtl numbers equal to 0.71 and 7, respectively. The above work is of interest, but it has serious disadvantages, which will be analyzed below: 1. On p. 1363, the Eckert number Ec as a parameter is used. However, this parameter was not defined anywhere in the paper. Usually, this number is used when the viscous dissipation term is included into the energy equation. However, in the present problem no viscous dissipation term exists. 2. The assumption that, except for the applied external uniform magnetic field, a new magnetic field appears, which is induced by the electrically conducting fluid and which interacts with the external field, gives a fresh approach to the problem. However, the importance of the induced magnetic field depends on the magnetic Reynolds number defined [2] as Rm = μσul, where μ is the magnetic permeability, σ is the fluid electrical conductivity, u is the characteristic flow velocity, and l is the characteristic length scale. When the magnetic Reynolds number is much smaller than unity, the induced magnetic field is negligible, and the imposed external magnetic field is unaffected by the moving conducting fluid [2]. In most laboratory experiments or industrial processes, Rm is very low, being usually less than 10 [3]. In contrast, when the magnetic Reynolds number is equal to or greater than unity, the induced magnetic field is of importance and should be taken into account. Indeed, certain applications, such as advanced schemes for controlling magnetogasdynamic flows around hypersonic vehicles, involve the values of Rm in the range 1–10 [3]. In the discussed work [1], the author took into account the induced magnetic field without any reference to the magnetic Reynolds number that is the characteristic criterion. We can calculate Rm for air at 20 C. According to [4], at this temperature the electrical conductivity of air varies from 3⋅10 to 8⋅10 Ω⋅m, whereas the magnetic permeability is equal to 1.257⋅10 H/m [5]. For a typical velocity u = 1 m/ s and a typical length scale l = 0.1 m, the magnetic Reynolds number is Rm 3.8⋅10 . For water at 20C, σ = 10 Ω⋅m [6] and μ = 1.257⋅10 H/m [5]. Here, for typical velocity and length scale Rm = 1.257⋅10 . Instead of using the above-mentioned magnetic Reynolds number, the author of [1] used the parameter Pm, called the magnetic Prandtl number: Pm = σνμ, where ν is the fluid kinematic viscosity. In [1], all the results were obtained for air and water, which corresponds, in the author’s opinion, to Pm changing from 0.1 to 1. Let us calculate Pm for air at 20C. Here, ν = 1.827⋅10 m/s [7], so that we have Pm 6.9⋅10. For water ν = 9.8⋅10 m/s [7], and we obtain Pm = 1.23⋅10. Journal of Engineering Physics and Thermophysics, Vol. 86, No. 1, January, 2013

On the effectiveness of variable properties and thermophoresis on steady MHD heat and mass transfer over a porous flat surface

PurposeThe purpose of this paper is to examine the effects of thermophoresis and magnetic field on steady two‐dimensional laminar hydrodynamic flow with heat and mass transfer over a semi‐infinite permeable flat surface in the presence of viscous dissipation and thermal radiation effects. The fluid viscosity and thermal conductivity are assumed to vary as a function of temperature.Design/methodology/approachThe boundary layer equations are transformed to non‐linear ordinary differential equations using scaling group of transformations and these equations are solved numerically by using the fourth order Runge‐Kutta method with shooting technique for some values of physical parameters.FindingsSome of the results obtained for a special case of the problem are compared to the results published in previous work and are found to be in excellent agreement. Many results are obtained and a representative set is displayed graphically to illustrate the influence of the physical parameters involved in the problem on the velocity, temperature and concentration profiles, as well as the local skin‐friction coefficient, the wall heat transfer and the particle deposition rate.Research limitations/implicationsOne valuable, important observation is that the effect of the variable viscosity parameter is to increase the effect of all studied parameters in the boundary‐layer's flow field. Also, the skin‐friction coefficient, wall heat transfer and wall deposition flux in a fluid of uniform viscosity are higher than in a fluid of non‐uniform viscosity when the surface is permeable.Originality/valueThe paper presents a numerical solution for two‐dimensional boundary‐layer flow with heat and mass transfer over a semi‐infinite permeable flat surface. Numerical results indicate that the combining effects of magnetic field and radiation strongly controls flow and mass transfer characteristics for the thermophoretic hydrodynamic flow. This problem is interesting from the physical point of view and also for its applications in engineering sciences.

Effect of variations in viscosity and thermal diffusivity on MHD heat and mass transfer flow over a porous inclined radiate plane

This article is focused on the effectiveness of variable viscosity and variable thermal diffusivity on steady MHD heat and mass transfer flow over a semi-infinite porous inclined plate in the presence of thermal radiation and thermophoresis. The governing fundamental equations are transferred into a system of nonlinear similar ordinary differential equations, which are solved numerically by using Chebyshev pseudospectral method. Favorable comparisons with previously published work are performed and the results are found to be in very good agreement. Numerical results for the dimensionless velocity, temperature and concentration profiles as well as for the skin-friction coefficient, wall heat transfer and particle deposition rate are obtained and displayed graphically for pertinent physical parameters to show interesting aspects of the solutions.

A study of induced magnetic field with chemically reacting and radiating fluid past a vertical permeable plate

The influence of thermal radiation and chemical reaction on the steady MHD heat and mass transfer by a mixed convective flow of a viscous, incompressible, electrically conducting Newtonian fluid (an optically thin gray gas) past a vertical permeable plate was investigated with account for the induced magnetic field. The similarity solutions of the transformed nondimensional governing equations are obtained by the series solution technique. The influence of numerous parameters on the process characteristics is studied.

Induced magnetic field with radiating fluid over a porous vertical plate: analytical study

The objective of this investigation is to study the influence of thermal radiation and magnetic Prandtl number on the steady MHD heat and mass transfer by mixed convection flow of a viscous, incompressible, electrically-conducting, Newtonian fluid which is an optically thin gray gas over a vertical porous plate taking into account the induced magnetic field. The similarity solutions of the transformed dimensionless governing equations are obtained by series solution. It is found that, velocity is reduced considerably with a rise in conduction-radiation parameter (R) or Hartmann number (M) whereas the skin friction is found to be markedly boosted with an increase in M or Magnetic Prandtl number (Pm). An increase in magnetic body parameter (M) or Magnetic Prandtl number (Pm) is found to escalate induced magnetic field whereas an increase in R is shown to exert the opposite effect. Applications of the study include laminar magneto-aerodynamics, materials processing and MHD propulsion thermo-fluid dynamics.DOI: 10.3329/jname.v7i2.5662