Aircooling
Encyclopedia
Air cooling is a method of dissipating heat
. It works by making the object to be cooled have a larger surface area or have an increased flow of air over its surface, or both. An example of the former is to add 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. In many cases the addition of fins adds to the total surface area making a heatsink that makes for greater efficiency in cooling.
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).
s 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.
processes use air as a cooling medium, either directly or indirectly. Air conditioning
is a very common process in which the air in a room, or a whole building, is cooled in order to maintain a comfortable environment for its occupants. Often the air has been cooled by chilled water or brine
and the heat transferred to that medium is transported outside the building where, often, fan-driven water-to-air heat exchanging
is again effected to reject the heat into the atmosphere. A common sight around, for example, power station
s are the large waisted concrete towers that emit steam more or less constantly. These are, in part, using air cooling on a grand scale.
A rule-of-thumb formula 1 + (-1/17500) * h = derating factor. Where h is the height over sea level in meters. And the result is the factor that should be multiplied with the cooling capacity in [W] to get the cooling capacity at the specified height over sea level.
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
. It works by making the object to be cooled have a larger surface area or have an increased flow of air over its surface, or both. An example of the former is to add 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
Fan (mechanical)
A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...
blowing air into or onto the object one wants to cool. In many cases the addition of fins adds to the total surface area making a heatsink that makes for greater efficiency in cooling.
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).
Examples
Vehicles
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 automobiles are rarer. The most common example is the Flat engine or Boxer engine, once used extensively by Porsche and still in use on BMWs.Notable past models include the Volkswagen Beetle and related models, the Citroën 2CV, the Chevrolet Corvair and the Porsche 911 until 1998.Turbines
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.Electronics
Its use is widespread in computers and CPU cooling, where the computer processorCentral processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
s 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
Electrical insulation
thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...
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.
Industries
A very large number of industrialIndustry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...
processes use air as a cooling medium, either directly or indirectly. Air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
is a very common process in which the air in a room, or a whole building, is cooled in order to maintain a comfortable environment for its occupants. Often the air has been cooled by chilled water or brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...
and the heat transferred to that medium is transported outside the building where, often, fan-driven water-to-air heat exchanging
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
is again effected to reject the heat into the atmosphere. A common sight around, for example, power station
Power station
A power station is an industrial facility for the generation of electric energy....
s are the large waisted concrete towers that emit steam more or less constantly. These are, in part, using air cooling on a grand scale.
Derating at high altitude
When operating in an environment with lower air pressure like high altitude or airplane cabins. The cooling capacity has to be derated compared to that of sea level.A rule-of-thumb formula 1 + (-1/17500) * h = derating factor. Where h is the height over sea level in meters. And the result is the factor that should be multiplied with the cooling capacity in [W] to get the cooling capacity at the specified height over sea level.
See also
- Computer coolingComputer coolingComputer cooling is required to remove the waste heat produced by computer components, to keep components within their safe operating temperature limits.Various cooling methods help to improve processor performance or reduce the noise of cooling fans....
- Computer fanComputer fanA computer fan is any fan inside, or attached to, a computer case used for cooling purposes, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heatsink to cool a particular component...
- Evaporative cooling
- Water cooling
- Oil coolingOil coolingOil cooling refers to a process whereby heat is displaced from a 'hotter' object, into a cooler oil and is the principle behind oil cooler devices. The oil carrying the displaced heat usually passes through a cooling unit such as a radiator or less commonly a gas decompresser...
- Heat pipeHeat pipeA heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces....
cooling - Peltier cooling
- Heater coreHeater CoreA heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air...