Air cooling is a way of dispersing heat. By enlarging the surface area of the item to be cooled or by intensifying the circulation of air over the surface, air cooling becomes effective at dissipating heat. To operate effectively, the object or surface from which the heat will be extracted cannot be cooler than the air. This can be attributed to the second law of thermodynamics, which states that heat can only move from a hot receptacle to a cold receptacle.
Generally, air is used for cooling an internal combustion engine (ICE) where fuel combustion occurs with an oxidizer, such as air, in a combustion chamber. The combustion chamber is the part of the engine that burns fuel. The air cooling of an ICE commonly occurs in aircraft, because the fluid in the engine is easily accessible, and is typically at the temperature needed to operate efficiently.
Although most ICE are referred to as "liquid cooled," the air flowing through the radiator or heat exchanger is actually responsible for the cooling liquid. It is less common to find this type of air cooling in automobiles; the most frequent and appropriate example is the flat engine, which was once widely used by Porsche. A flat engine is an ICE with several cylindrical parts all moving in the horizontal direction.
Air cooling can also be seen in gas turbine engines, such as turbojets. These engines are comprised of rotors, which are vulnerable to the hot gases departing the combustion chamber. To prevent the rotors' blades and vanes from melting, the compression system supplies the cold air necessary to cool them.
Air cooling is also commonly used in computers. If the significant amount of heat that the computer processors produce is not dissipated, the central processing unit and other electronics parts could be destroyed. In situations such as these, moving air can be an efficient guard against the heat created from flow of electric current.
Industrial air cooling exists in a large number of companies. In this environment, air is used as a direct or indirect cooling method. Through air conditioning, an entire room or building is cooled so its occupants have a comfortable atmosphere. Chilled water is used to cool the air, and heat is detoured to outside the building. In order to deny the heat access into the environment, a fan-driven, water-to-air device designed for effective heat transfer is effected.