Natural Convection

Natural convection can occur when the solid surface temperature is different from the surrounding fluid. For example, natural convection can take place between a heated (or cooled) vertical (or horizontal) plate or tube and the surrounding fluid. This chapter illustrates the velocity profile, temperature profile, and heat transfer from a hot vertical wall to a cold fluid due to natural convection. The key parameter/driving force to determine natural convection is Grashof number, a ratio of buoyancy force to viscous force (buoyancy force tries to move the fluid up but viscous force tries to resist it from moving). Another parameter is Prandtl number, a fluid property showing the ratio of kinematic viscosity to thermal diffusivity. The product of Grashof number with Prandtl number is called Rayleigh number, another way of measuring the natural convection. Natural convection is due to temperature difference between the surface and fluid and the gravity force.