Mixed convection heat and surface mass transfer between power-law fluids and rotating permeable bodies

Abstract

Mixed thermal convection analyses of rotating porous bodies placed in power-law fluids are important for the basic understanding and improved design of various chemical and mechanical engineering systems. Of interest are the coupled effects of steady, laminar free-forced convection heat transfer, body spin, wall heating/cooling mode, wall mass transfer, and the type of fluid on the local skin friction and heat transfer coefficient. Concentrating on a rotating sphere with fluid injection/suction at the wall, the uniquely transformed boundary-layer equations are solved using an implicit finite difference method. The validated computer simulation results indicate the following. Depending on the magnitude of the body surface temperature, the buoyancy force may reverse the roles of injection and suction effects on the skin friction group. Shear-thickening fluids and body spin accelerate boundary-layer separation. Body rotation, fluid withdrawal, and high Prandtl numbers all enhance heat transfer. The unique behavior of the heat transfer group near the stagnation point for different power-law fluids ( ng̊1) in conjuction with body rotation is discussed. The velocity overshoot in buoyancy aiding flow and flow retardation in opposing flow with early boundary-layer separation are analyzed.