ABSTRACT
Convective heat transfer involves the combination of molecular diffusion of heat and bulk fluid motion. The bulk motion of the fluid significantly affects the rate of heat transfer, detailed knowledge of the fluid velocity and pressure distributions are essential in convection problems. In general, the type of convection problem can be categorized based on the magnitude of the convective heat transfer coefficient. Natural convection, or free convection, occurs due to temperature differences which affect the density and hence lead to buoyancy forces that drive the fluid motion. Convection has an important role in many engineering and scientific processes. The convection governing equations include the conservation of mass, momentum, and energy, as well as the second law of thermodynamics. The effective thermal conductivity represents a thermal conductivity of a stationary fluid that produces the same amount of heat transfer as the actual moving fluid due to free convection between the concentric spheres.
