The paper discusses the effects of homogeneous-heterogeneous reactions on stagnation-point flow of a nanofluid over a stretching or shrinking sheet. The model presented describes mass transfer in copper-water and silver-water nanofluids. The governing system of equations is solved numerically, and the study shows that dual solutions exist for certain suction/injection, stretching/shrinking and magnetic parameter values. Comparison of the numerical results is made with previously published results for special cases.

The flow, heat and mass transfer characteristics of the free convection on a vertical plate with uniform and constant heat and mass fluxes in a doubly stratified micropolar fluid saturated non-Darcy porous medium are studied. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms by pseudo-similarity variables. The resulting system of equations is then solved numerically using the Keller-box method. The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation. The effects of the micropolar, Darcy, non-Darcy and stratification parameters on the dimensionless velocity, microrotation, wall temperature, wall concentration, local skin-friction coefficient and wall couple stress coefficient are presented graphically.

This paper investigates the influence of viscous dissipation and magnetic field on natural convection from a vertical plate in a non-Darcy porous medium saturated with a nanofluid. In addition, a convective boundary condition is incorporated in the nanofluid model. A nonsimilarity transformation is used to reduce the mass, momentum, thermal energy, and the nanoparticle concentration equations into a set of nonlinear partial differential equations. The obtained equations are solved numerically by an accurate implicit finite-difference method. The accuracy of the numerical results is validated by a quantitative comparison of the heat transfer rates with previously published results for a special case and the results are found to be in good agreement. The effects of magnetic field, viscous dissipation, and non-Darcy and the convection parameters on the velocity, temperature, nanoparticle volume fraction, and heat and nanoparticle mass transfer rates are illustrated graphically.

In this article, we investigate the effects of Arrhenius activation energy with binary chemical reaction and convective boundary condition on natural convective flow over vertical frustum of a cone in a Buongiorno nanofluid under the presence of thermal radiation. The zero nanoparticle flux condition is used at the surface of frustum of a cone rather than the uniform wall condition to execute physically applicable results. For this complex flow model, a suitable non-similarity transformations are used initially and then Bivariate pseudo-spectral local linearisation method is used to solve the non-similar, coupled partial differential equations. Further, the convergence test and error analysis are conducted to verify the accuracy of numerical method. The effects of flow influenced parameters on the non-dimensional velocity, temperature, nanoparticle volume fraction and regular concentration profiles as well as on the skin friction, heat transfer rate, nanoparticle and regular mass transfer rates are analyzed.

A numerical approach has been used to analyze the effects of homogeneous-heterogeneous reaction and nonlinear density temperature variation over a vertical plate in an incompressible micropolar fluid flow saturated Darcy porous medium. In addition, convective boundary condition is incorporated in a micropolar fluid model. The similarity representation for the set of partial differential equations is attained by applying Lie group transformations. The resulting non-dimensional equations are worked out numerically by spectral quasi-linearization method. Less temperature and wall couple stress coefficient, but more velocity, skin friction, species concentration, and heat transfer rate are noticed by enhancing the nonlinear convection parameter. It is also observed that as the strength of homogeneous and heterogeneous reaction parameters increases, the species concentration and mass transfer rate reduces.

The significance of the Soret effect on the boundary-layer stagnation-point flow past a stretching/shrinking sheet in a nanofluid-saturated non-Darcy porous medium is investigated in this study. The nanofluid-saturated porous medium is considered by incorporating the Brownian motion and thermophoresis effects. A similarity transformation is used to reduce the governing fluid flow equations into a set of differential equations and then solved numerically by an accurate implicit finite-difference method. The flow; temperature; concentration and nanoparticle concentration fields; skin friction coefficient; and heat, mass, and nanoparticle mass transfer rates are affected by the complex interactions among the various physical parameters involved in the analysis. These profiles are illustrated graphically in order to reveal interesting phenomena.

In this study, the effects of viscous dissipation on mixed convection heat and mass transfer along a vertical plate embedded in a nanofluid‐saturated non‐Darcy porous medium have been investigated. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The new far‐field thermal boundary condition that has been recently developed is employed to properly account for the effect of viscous dissipation in mixed convective transport in a porous medium. The nonlinear governing equations and the associated boundary conditions are transformed to a set of nonsimilar ordinary differential equations and the resulting system of equations is then solved numerically by an improved implicit finite‐difference method. The effect of the physical parameters on the flow, heat transfer, and nanoparticle concentration characteristics of the model are presented through graphs and the salient features are discussed. As expected, a significant improvement in the heat transfer coefficient is noticed because of the consideration of the nanofluid in the porous medium. With the increase in the value of the viscous dissipation parameter, a reduction in the non‐dimensional heat transfer coefficient is noted while an increase in the nanoparticle mass transfer coefficient is seen. Further, an increase in the mixed convection parameter lowered both the heat and nanoparticle mass transfer rates. Moreover, the increase in the Brownian motion parameter enhanced the nanoparticle mass transfer rate but it reduced the heat transfer rate in the boundary layer. A similar trend is also found with the thermophoresis parameter. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(5): 397–411, 2014; Published online 3 October 2013 in Wiley Online Library (http://wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21083

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