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In this paper, we present a theoretical study of the combined effects of activation energy and binary chemical reaction in an unsteady mixed convective flow over a boundary of infinite length. The current study incorporates the influence of the Brownian motion, thermophoresis and viscous dissipation on the velocity of the fluid, temperature of the fluid and concentration of chemical species. The equations are solved numerically to a high degree of accuracy using the spectral quasilinearization method. Brownian motion was noted as the main process by which the mass is transported out of the boundary layer. The effect of thermophoretic parameter seems to be contrary to the expected norm. We expect the thermophoretic force to ‘push’ the mass away from the surface thereby reducing the concentration in the boundary layer, however, concentration of chemical species is seen to increase in the boundary layer with an increase in the thermophoretic parameter. The use of a heated plate of infinite length increased the concentration of chemical species in the boundary layer. The Biot number which increases and exceeds a value of one for large heated solids immersed in fluids increases the concentration of chemical species for its increasing values. Highlights Combined effects of activation energy and binary chemical reaction are proposed. Spectral quasi-linearization method (SQLM) is used for computer simulations. Use Arrhenius activation energy in the chemical species concentration. Validate the accuracy and convergence using residual error analysis.

The effects of a homogeneous-heterogeneous reaction on steady micropolar fluid flow from a permeable stretching or shrinking sheet in a porous medium are numerically investigated in this paper. The model developed by Chaudhary and Merkin (Fluid Dyn. Res. 16:311-333, 1995) for a homogeneous-heterogeneous reaction in boundary layer flow with equal diffusivities for reactant and autocatalysis is used and extended in this study. The uniqueness of this problem lies in the fact that the solutions are possible for all values of the stretching parameter λ > 0, while for λ < 0 (shrinking surface), solutions are possible only for a limited range of values. The effects of physical and fluid parameters such as the stretching parameter, micropolar parameter, permeability parameter, Schmidt number, strength of homogeneous and heterogeneous reaction parameter on the skin friction, velocity and concentration are analyzed, and these results are presented through graphs. The solute concentration at the surface is found to decrease with the strength of the homogeneous reaction, and to increase with heterogeneous reactions, the permeability parameter and stretching or shrinking parameters. The velocity at the surface was found to increase with the micropolar parameter.

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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 stagnation-point flow of an incompressible non-Newtonian Casson fluid over a stretching sheet in the presence of Soret and Dufour effects is investigated. The resulting partial differential equations are reduced to a set of nonlinear ordinary differential equations using similarity transformations and solved using the Matlab bvp4c package. A comparison is made with the results available in the literature and found to be in good agreement. Dual solutions for the velocity, temperature, concentration and skin friction were obtained for some special cases when the stretching parameter is negative. The effect of the Casson parameter on the skin friction, heat transfer and mass transfer rates is discussed.

We investigate the effects of momentum, thermal, and solute slip boundary conditions on nanofluid boundary layer flow along a permeable surface. The conventional no-slip boundary conditions at the surface are replaced by slip boundary conditions. At moderate to high temperatures, the temperature-concentration dependence relation is nonlinear and the Soret effect is significant. The governing partial differential equations are solved numerically. The influence of significant parameters on the fluid properties as well as on the skin friction, local Nusselt number, local Sherwood number, and the local nanoparticle Sherwood number are determined. We show, among other results, that the existence and uniqueness of the solutions depends on the slip parameters, and that the region of existence of the dual solution increases with the slip parameters.