Mixed Convection flow of Chemically reacting Couple Stress fluid in an annulus with Soret and Dufour effects K. KALADHAR Department of Mathematics National Institute of Technology Puducherry Karaikal- 609 605 INDIA kkr.nitpy@gmail.com D. SRINIVASACHARYA Department of Mathematics National Institute of Technology Warangal INDIA dsrinivasacharya@yahoo.com Abstract: In this paper, mixed convection flow of couple stress fluid in circular annulus is studied. First order chemical reaction, Soret and Dufour effects are taken into consideration. The governing partial differential equa- tions are transformed into a system of ordinary differential equations and solved by Homotopy Analysis Method (HAM). The effects of Soret number, Dufour number, chemical reaction parameter and couple stress parameter on the dimensionless velocity, temperature and concentration are analyzed graphically. Key–Words: Mixed convection, Couple stress fluid, Soret and Dufour effects, Chemical reaction, HAM. 1 Introduction Mixed convection heat transfer and fluid flow in an annulus between two vertical concentric cylinders is the focus of investigation over the past years due to its wide range of practical applications. These applica- tions include electrical machineries where heat trans- fer occurs in the annular gap between the rotor and stator, growth of single silicon crystals, heat exchang- ers, cooling systems for electronic devices, solar col- lectors and other rotating systems [1, 2]. Several stud- ies on the flow between two circular cylinders coupled with heat and mass transfer have appeared in the lit- erature [3, 4, 5]. All the above mentioned attempts describe the flow analysis without chemical reaction. Chemical reactions can be codified as either het- erogeneous or homogeneous processes. This depends on whether they occur at an interface or as a single phase volume reaction. In most cases of chemical re- actions, the reaction rate depends on the concentra- tion of the species itself. In many materials processing systems chemical reaction effects may exert a signif- icant role. These include co current buoyant upward gas-liquid flow in packed bed electrodes [6], Sodium Oxide-Silcon dioxide glass melt flows [7], electro- chemical generation of elemental bromine in porous electrode systems [8] and the manufacture of intumes- cent paints for fire safety applications [9]. Further, research on combined heat and mass transfer with chemical reaction and thermophoresis effect can help to design for chemical processing equipment, forma- tion and dispersion of fog, distribution of tempera- ture and moisture over agricultural fields as well as groves of fruit trees, damage of crops due to freezing, food processing, cooling towers, chemically-reactive vapour deposition boundary layers in optical materi- als processing, catalytic combustion boundary layers, chemical diffusion in disk electrode modeling and car- bon monoxide reactions in metallurgical mass transfer and kinetics. Several investigators have examined the effect of chemical reaction on the flow, heat and mass transfer through channels [10, 11], past a flat plate [12, 13, 14] and through concentric cylinders [15]. In all the above studies Soret and Dufour ef- fects are neglected on the basis that they are of a smaller order of magnitude than the effects described by Fourier’s and Fick’s laws. However, when chem- ical species are introduced at a surface in fluid do- main, with different (lower) density than the surround- ing fluid, both Soret (thermo-diffusion) and Dufour (diffusion-thermal) effects can be influential. In com- bined heat and mass transfer processes, the thermal energy flux resulting from concentration gradients is referred to as the Dufour or diffusion thermal effect. Similarly, the Soret or thermo-diffusion effect is the contribution to the mass fluxes due to temperature gra- dients. These effects are considered as second or- der phenomena and may become significant in areas such as hydrology, petrology, geosciences, etc. The Soret effect, for instance, has been utilized for iso- tope separation and in mixture between gases with very light molecular weight and of medium molecular weight. The Dufour effect was found to be of order of considerable magnitude such that it cannot be ne- WSEAS TRANSACTIONS on HEAT and MASS TRANSFER K. Kaladhar, D. Srinivasacharya E-ISSN: 2224-3461 84 Volume 9, 2014