Steady and unsteady aligned magnetohydrodynamics free convection flows of magnetic and non magnetic nanofluids along a wedge, vertical and inclined plates

Abstract

Nanofluids are a new type of heat transfer fluid engineered by uniform and stable suspension of nanometer sized particles into liquids. The heat transfer in nanofluids is important especially in the context of chemical engineering, aerospace engineering and industrial manufacturing processes. The reason is that, nanofluids were found to transfer heat more efficiently than the conventional fluids. Therefore, nanofluids research could lead to a major breakthrough in developing next generation coolants for numerous engineering applications. Due to this reason, several flow problems related to heat transfer over vertical flat plate, inclined plate and wedge were studied in this thesis. The main purpose of this study was to investigate the characteristics of two dimensional flow and surface heat transfer for two cases which are steady and unsteady convection flows. Nanofluids with two different base fluids (water and kerosene) containing magnetic and non magnetic nanoparticles were considered. The effect of magnetohydrodynamics (MHD) on the flow and heat transfer was also studied. The study starts with the formulation of the mathematical models that governed the fluid flow and heat transfer. Next, the governing nonlinear equations in the form of partial differential equations were reduced into ordinary differential equations using appropriate similarity transformation. The resulting systems of ordinary differential equations were then solved numerically using Keller box method. The numerical values of the skin friction coefficient, the local Nusselt number which represents the heat transfer rate at the surface as well as the velocity and temperature profiles were obtained for various values of the magnetic field inclination angle, magnetic interaction, plate inclination angle, nanoparticles volume fraction, wedge angle, moving wedge, unsteadiness, Grashof number and thermal buoyancy. All results obtained, were displayed graphically in addition to tabular form. The comparisons of results with previous studies were made to validate the results. For both steady and unsteady problems, it is found that magnetic field inclination angle can be used as controlling factor for certain situation because it enhances the skin friction and heat transfer rate. The plate inclination angle parameter and nanoparticles volume fraction parameter have tendency to increase momentum and thermal boundary layers thickness. For unsteady problems, it is observed that the unsteadiness parameter has significant effect on the nanofluids motion and heat transfer characteristic.