An external convection problem refers to the study of heat and mass transfer between a solid surface and a moving fluid, such as air or water, in an open environment. This type of convection involves the transfer of heat or mass due to the motion of the fluid over the surface.
The rate of external convection is affected by several factors, including the velocity and temperature of the fluid, the properties of the fluid (such as its density and viscosity), and the geometry and surface characteristics of the solid body.
External convection occurs when the fluid is in contact with only one side of the solid surface, while internal convection involves the fluid being enclosed within a solid surface, such as in a pipe or duct. The heat transfer mechanisms and governing equations for these two types of convection are different.
External convection is important in many engineering and natural systems, such as in the design of heat exchangers, cooling of electronic devices, and atmospheric and oceanic circulation. It also plays a role in everyday activities, such as cooking and heating and cooling of buildings.
External convection is typically studied through theoretical analysis, numerical simulations, and experimental measurements. The governing equations, such as the Navier-Stokes equations and the energy equation, are solved to determine the heat and mass transfer rates. Experimental techniques, such as wind tunnels and thermal imaging, are also used to validate theoretical and numerical results.