CFD ANALYSIS OF AIDING BUOYANCY MIXED CONVECTION IN NON- NEWTONIAN FLUIDS FLOW OVER A CHANNEL CONFINED CIRCULAR CYLINDER

Abstract

Mixed convection heat transfer from a heated vertical circular cylinder in a confined channel immersed in incompressible power-law fluid is considered herein under the steady flow regime. In this arrangement, the fluid is flowing in vertical upward direction whereas gravity is acting downwards, which results in the aiding buoyancy flow configuration where the buoyancy may be cross, adding or opposing depending on the direction of the externally opposed flow.The dependence of density on the temperature is accounted by the Bouissneq approximation. The temperature gradient between the cold fluid and hot bluff bodies is assumed to be low. The suitable forms of the continuity, momentum and thermal energy equations are solved by using COMSOL Multiphysics which uses the finite element method inbuilt solver. The convective terms in the momentum and energy equations are discretized using the QUICK scheme. The numerical solution of the flow governing equations are obtained for the following ranges of the parameters, i.e., Reynolds number (1 ≤ Re≤ 40), and Prandtl number (1 ≤ Pr ≤ 100), Richardson number, (0 ≤ Ri ≤ 2) and power-law index (0.2≤ n≤ 1.8). The effects of these dimensionless parameters on the detailed local and global kinematics of flow and heat transfer characteristics such as streamline, vorticity, pressure profiles, individual and total drag coefficients and local and average Nusselt numbers have been explored in this work. For fixed value of Ri, Re and Pr with increases the power law-index, the value of Nusselt number and pressure drag coefficient for cylinder decrease, but viscous drag coefficient increases. If blockage ratio increases then it leads to decrease in the value of Nusselt number. Nusselt number also showed a direct correlation with Reynolds number, with increasing value of Reynolds number the value of Nusselt number decreases drastically. For better representation of effects streamline profiles, isothermal profiles, and vorticity profile has been incorporated in this thesis.