Thermal dispersion effects on convective heat and mass transfer in an Ostwald de Waele nanofluid flow in porous media
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RESEARCH
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Thermal dispersion effects on convective heat and mass transfer in an Ostwald de Waele nanofluid flow in porous media Peri K Kameswaran and Precious Sibanda* * Correspondence: [email protected] School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Private Bag X01 Scottsville, Pietermaritzburg, 3209, South Africa
Abstract In this paper we investigate the effects of thermal dispersion on non-Newtonian power-law nanofluid flow over an impermeable vertical plate. We use a mathematical model for the nanofluid that incorporates the effects of nanoparticle Brownian motion and thermophoresis. The non-Newtonian nature of the fluid is modeled by the power-law index n, and both cases of shear thinning and thickening are investigated. The governing set of equations is solved numerically using the shooting technique. The effects of physical and fluid parameters on the properties are determined for both instances of aiding and opposing buoyancy force. We show, inter alia, that for fixed thermal dispersion coefficient values, the fluid temperature within the boundary layer decreases as the power-law index increases for both aiding and opposing buoyancy case. Keywords: non-Newtonian nanofluid; natural convection; thermal dispersion; porous medium
1 Introduction The study of a non-Newtonian power-law fluid model is important in simulating the rheological characteristics of numerous fluids such as used in food preparation, bio-chemical and pharmaceutical industries. Many interesting applications of non-Newtonian powerlaw fluids were presented by Shenoy []. Such non-Newtonian fluids may be important in, for instance, the physiological transport of biological solutions, polymer melts, paints, etc. (Ellahi et al. []). Rastogi and Poulikakos [] examined the problem of double diffusion from a plate in a porous medium saturated with a non-Newtonian power-law fluid. The effect of double dispersion on natural convection heat and mass transfer in a nonNewtonian fluid saturated non-Darcy porous medium was studied by Kairi et al. []. They observed that the heat transfer rate increases with the thermal dispersion effect for both pseudoplastics and dilatant fluids. In recent years, the study of convective heat transfer in nanofluids has received a lot of attention. Nanofluids which are suspensions of solid nanoparticles in conventional liquids like water, oil and ethylene glycol have many potential applications in industry. Convection in nanofluid flows in porous media has also received attention due to its potential application in materials processing and solar energy collector devices. Nield and Kuznetsov [] extended the Cheng-Minkowycz problem for heat transfer in porous media to nanofluids. Uddin et al. [] used the lie group analysis to study non-Newtonian nanofluid flow in a ©2013 Kameswaran and Sibanda; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribu
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