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Article
Publication date: 9 November 2012

Mamun Molla, Suvash C. Saha and M.A.I. Khan

The purpose of this paper is to discuss, with numerical simulations, magnetohydrodynamic (MHD) natural convection laminar flow from an isothermal horizontal circular…

Abstract

Purpose

The purpose of this paper is to discuss, with numerical simulations, magnetohydrodynamic (MHD) natural convection laminar flow from an isothermal horizontal circular cylinder immersed in a fluid with viscosity proportional to a linear function of temperature.

Design/methodology/approach

The governing boundary layer equations are transformed into a non‐dimensional form and the resulting nonlinear system of partial differential equations are reduced to convenient form, which are solved numerically by two very efficient methods: implicit finite difference method together with Keller box scheme; and direct numerical scheme.

Findings

Numerical results are presented by velocity and temperature distributions of the fluid as well as heat transfer characteristics, namely the shearing stress and the local heat transfer rate in terms of the local skin‐friction coefficient and the local Nusselt number for a wide range of MHD parameter, viscosity‐variation parameter and viscous dissipation parameter.

Originality/value

MHD flow in this geometry with temperature dependent viscosity is absent in the literature. IN this paper, the results obtained from the numerical simulations have been verified by two methodologies.

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Article
Publication date: 16 January 2007

M.A. Mehrabian and M. Khoramabadi

The purpose of this paper is to investigate numerically the influence of variable fluid viscosity on thermal characteristics of plate heat exchangers for counter‐flow and…

Abstract

Purpose

The purpose of this paper is to investigate numerically the influence of variable fluid viscosity on thermal characteristics of plate heat exchangers for counter‐flow and steady‐state conditions.

Design/methodology/approach

The approach to fulfill the purpose of the paper is to derive the one‐dimensional energy balance equations for the cold and hot streams in the adjacent channels of a plate heat exchange composed of four corrugated plates. A finite difference method has been used to calculate the temperature distribution and thermal performance of the exchanger. Water is used as the hot liquid being cooled in the side channels, while a number of working fluids whose viscosity variation versus temperature is more severe were used as the cold fluid being heated in the central channel.

Findings

The program is run for a combination of working fluids such as water‐water, water‐isooctane, water‐benzene, water‐glycerin and water‐gasoline. The temperature distributions of both streams have been plotted along the flow channel for all the above combination of working fluids. The overall heat transfer coefficients have also been plotted against both cold and hot fluid temperatures. It is found that the overall heat transfer coefficient varies linearly with respect to either cold or hot fluid temperature within the temperature ranges applied in the paper. The exchanger effectiveness is not significantly affected when either the temperature dependent viscosity is applied or the nature of cold liquid is changed.

Originality/value

This paper contains a new method of numerical solution of energy balance equations for the thermal control volumes bounded by two plates. A comparison of the calculated results with documented experimental results validates the numerical method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 17 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 4 January 2016

Jawali C Umavathi, A J Chamkha and Syed Mohiuddin

The purpose of this paper is to investigate the effect of exponential viscosity-temperature relation, exponential thermal conductivity-temperature relation and the…

Abstract

Purpose

The purpose of this paper is to investigate the effect of exponential viscosity-temperature relation, exponential thermal conductivity-temperature relation and the combined effects of variable viscosity and variable thermal conductivity on steady free convection flow of viscous incompressible fluid in a vertical channel.

Design/methodology/approach

The governing equations are solved analytically using regular perturbation method. The analytical solutions are valid for small variations of buoyancy parameter and the solutions are found up to first order for variable viscosity. Since the analytical solutions have a restriction on the values of perturbation parameter and also on the higher order solutions, the authors resort to numerical method which is Runge-Kutta fourth order method.

Findings

The skin friction coefficient and the Nusselt number at both the plates are derived, discussed and their numerical values for various values of physical parameters are presented in tables. It is found that an increase in the variable viscosity enhances the flow and heat transfer, whereas an increase in the variable thermal conductivity suppresses the flow and heat transfer for variable viscosity, variable thermal conductivity and their combined effect.

Originality/value

This research is relatively original as, to the best of the authors’ knowledge, not much work is done on the considered problem with variable properties.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 October 2006

Mamun Molla and Anwar Hossain

To investigate the effects of chemical reaction on natural convection heat and mass transfer from a sphere with temperature dependent viscosity.

Abstract

Purpose

To investigate the effects of chemical reaction on natural convection heat and mass transfer from a sphere with temperature dependent viscosity.

Design/methodology/approach

The governing boundary layer equations are transformed into a non‐dimensional form and the resulting nonlinear system of partial differential equations are reduced to local non‐similarity boundary layer equations, which are solved numerically by very efficient implicit finite difference method together with Keller box scheme.

Findings

The effects of chemical reaction, the skin‐friction coefficients, surface heat transfer rates, velocity and concentration distribution decrease as well as the mass transfer rates and temperature distribution increase within the boundary layer.

Research limitations/implications

The investigation is valid for steady two‐dimensional laminar flow. The concentration of the reactant is maintained at a constant value and the sphere is isothermal. An extension to unsteady flow with temperature dependent thermal conductivity is left for future work.

Originality/value

This result provides guidance to engineers about heat and mass transfer with the effects of chemical reaction from isothermal spherical surface.

Details

Engineering Computations, vol. 23 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 6 June 2016

Ashraf Muhammad, Ali J Chamkha, S Iqbal and Masud Ahmad

The purpose of this paper is to report a numerical solution for the problem of steady, two dimensional boundary layer buoyant flow on a vertical magnetized surface, when…

Abstract

Purpose

The purpose of this paper is to report a numerical solution for the problem of steady, two dimensional boundary layer buoyant flow on a vertical magnetized surface, when both the viscosity and thermal conductivity are assumed to be temperature-dependent. In this case, the motion is governed by a coupled set of three nonlinear partial differential equations, which are solved numerically by using the finite difference method (FDM) by introducing the primitive variable formulation. Calculations of the coupled equations are performed to investigate the effects of the different governing parameters on the profiles of velocity, temperature and the transverse component of magnetic field. The effects of the thermal conductivity variation parameter, viscosity variation parameter, magnetic Prandtl number Pmr, magnetic force parameter S, mixed convection parameter Ri and the Prandtl number Pr on the flow structure and heat transfer characteristics are also examined.

Design/methodology/approach

FDM.

Findings

It is noted that when the Prandtl number Pr is sufficiently large, i.e. Pr=100, the buoyancy force that driven the fluid motion is decreased that decrease the momentum boundary layer and there is no change in thermal boundary layer is noticed. It is also noted that due to slow motion of the fluid the magnetic current generates which increase the magnetic boundary layer thickness at the surface. It is observed that the momentum boundary layer thickness is increased, thermal and magnetic field boundary layers are decreased with the increase of thermal conductivity variation parameter =100. The maximum boundary layer thickness is increased for =100 and there is no change seen in the case of thermal boundary layer thickness but magnetic field boundary layer is deceased. The momentum boundary layer thickness shoot quickly for =40 but is very smooth for =50.There is no change is seen for the case of thermal boundary layer and very clear decay for =40 is noted.

Originality/value

This work is original research work.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 20 September 2011

A.J. Chamkha, S.M.M. EL‐Kabeir and A.M. Rashad

The purpose of this paper is to consider heat and mass transfer by natural convection from a vertical cylinder in porous media for a temperaturedependent fluid viscosity

Abstract

Purpose

The purpose of this paper is to consider heat and mass transfer by natural convection from a vertical cylinder in porous media for a temperaturedependent fluid viscosity in the presence of radiation and chemical reaction effects.

Design/methodology/approach

The governing equations are transformed into non‐similar differential equations and then solved numerically by an efficient finite‐difference method.

Findings

It is found that there are significant effects on the heat and mass transfer characteristics of the problem due to the variation of viscosity and radiation and chemical reaction effects.

Originality/value

The paper combines the effects of radiation, chemical reaction, non‐Darcy porous media effects along with the variation of viscosity with temperature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 21 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 September 2003

W. Florez, H. Power and F. Chejne

This paper presents a boundary element method (BEM) based on a subdomain approach for the solution of non‐Newtonian fluid flow problems which include thermal effects and…

Abstract

This paper presents a boundary element method (BEM) based on a subdomain approach for the solution of non‐Newtonian fluid flow problems which include thermal effects and viscous dissipation. The volume integral arising from non‐linear terms is converted into equivalent boundary integrals by the multi‐domain dual reciprocity method (MD‐DRM) in each subdomain. Augmented thin plate splines interpolation functions are used for the approximation of field variables. The iterative numerical formulation is achieved by viewing the material as divided into small elements and on each of them the integral representation formulae for the velocity and temperature are applied and discretised using linear boundary elements. The final system of non‐linear algebraic equations is solved by a modified Newton's method. The numerical examples include non‐Newtonian problems with viscous dissipation, temperaturedependent viscosity and natural convection due to bouyancy forces.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 13 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 September 2001

M.A. Hossain and M.S. Munir

A steady, two‐dimensional natural convection flow of a viscous, incompressible fluid having temperaturedependent viscosity and thermal conductivity about a truncated cone…

Abstract

A steady, two‐dimensional natural convection flow of a viscous, incompressible fluid having temperaturedependent viscosity and thermal conductivity about a truncated cone is considered. We use suitable transformations to obtain the equations governing the flow in convenient form and integrate them by using an implicit finite difference method. Perturbation solutions are employed to obtain the solution in the regimes near and far away from the point of truncation. The results are obtained in terms of the local skin friction and the local Nusselt number. Perturbation solutions are compared with the finite difference solutions and found to be in excellent agreement. The dimensionless velocity, viscosity and thermal conductivity distributions are also displayed graphically, showing the effects of various values of the pertinent parameter for smaller values of Prandtl number.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 11 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 9 January 2009

P.R. Sharma and Gurminder Singh

Physical properties of a viscous fluid, e.g. viscosity and thermal conductivity change with temperature and in most of the studies concerned with natural convection…

Abstract

Purpose

Physical properties of a viscous fluid, e.g. viscosity and thermal conductivity change with temperature and in most of the studies concerned with natural convection, generally, the simultaneous effect of temperature dependent viscosity, thermal conductivity have been neglected. Hence, the purpose of this paper is to investigate the simultaneous effects of varying viscosity and thermal conductivity on free convection flow of a viscous incompressible electrically conducting fluid and heat transfer along an isothermal vertical non‐conducting plate in the presence of exponentially varying internal heat‐generation and uniform transverse magnetic field.

Design/methodology/approach

The governing equations of motion and energy are transformed into ordinary differential equations using similarity transformation. The resulting boundary valued, coupled and non‐linear differential equations are converted into system of linear differential equations and solved using Runge‐Kutta fourth order technique along with shooting method.

Findings

It was found that: fluid velocity decreases with the increase in magnetic parameter or Prandtl number; fluid temperature increases with the increase in magnetic parameter; velocity and temperature profiles increase due to increase in heat generation parameter; varying viscosity and thermal conductivity modifies the flow and heat transfer characteristic; and skin‐friction and heat transfer are affected by simultaneous change in viscosity and thermal conductivity in presence/absence of exponentially varying heat generation.

Research limitations/implications

The present study is applicable to an incompressible viscous fluid flow and heat transfer with linearly varying viscosity and thermal conductivity.

Originality/value

This paper provides useful information on the physical properties of a viscous fluid with regard to viscosity and thermal conductivity change with temperature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 25 May 2012

A.M. Salem

The 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…

Abstract

Purpose

The 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/approach

The 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.

Findings

Some 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/implications

One 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/value

The 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.

Details

Engineering Computations, vol. 29 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

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