Air cooling

Air cooling is a method of dissipating heat. It works by expanding the surface area of or increasing the flow of air over the object to be cooled, or both. An example of the former is to add cooling fins to the surface of the object, either by making them integral or by attaching them tightly to the object's surface (to ensure efficient heat transfer). In the case of the latter, it is done by using a fan blowing air into or onto the object one wants to cool. The addition of fins to a heat sink increases its total surface area, resulting in greater cooling effectiveness.

In all cases, the air has to be cooler than the object or surface from which it is expected to remove heat. This is due to the second law of thermodynamics, which states that heat will only move spontaneously from a hot reservoir (the heat sink) to a cold reservoir (the air).

Air is mainly used for air-cooled internal combustion engines (ICE), particularly those powering aircraft, because it is a readily available fluid and is often at a suitable temperature to be used efficiently. While many such ICE are called "liquid cooled" the cooling liquid is usually cooled by air passing through a radiator or heat exchanger. Examples of direct air cooling in modern automobiles are rare. The most common example is the flat engine or Boxer engine, once used extensively by Porsche and still in use on BMW motorcycles. Notable past models include the Volkswagen Beetle and related models, the Citroën 2CV, the Chevrolet Corvair and the Porsche 911 until 1998.

Gas turbine engines (e.g. turbojets, turbofans, etc.) incorporate turbines, which are exposed to the hot gases exiting the combustion chamber. Where necessary, relatively cold air is bled from the compression system and used to cool the turbine blades and vanes, to prevent them from melting.

Its use is widespread in computers and CPU cooling, where the computer processors produce large quantities of heat that, if not dissipated, could damage the CPU and other electronic components. In this case air has the advantage of being a good insulator too. However, in the future, new processors might generate too much heat to be dissipated through direct air cooling and it would follow that such direct cooling for computers and their components will become obsolete. Water cooling is somewhat popular in very high-power situations, such as large servers or heavily overclocked amateur systems.

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Wikipedia