An air conditioner (AC) is a system or a machine that treats air in a defined, usually enclosed area via a refrigeration cycle in which warm air is removed and replaced with cooler air.
In construction, a complete system of heating, ventilation, and air conditioning is called HVAC. Whenever Refrigeration is added it is called HVACR. Whether in homes, offices, or vehicles, its purpose is to provide comfort by altering the properties of the air, usually by cooling the air inside. The main function of an air conditioner is to change adverse temperatures.
In the 19th century British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate.
In 1842, American physician Dr. John Gorrie used compressor technology to create ice, which he used to cool air for his patients.[1] He hoped eventually to use his ice-making machine to regulate the temperature of buildings and even considered cooling entire cities with a system of centralized air conditioning units.
Air conditioning engineers broadly divide air conditioning applications into comfort and process.
Comfort applications aim to provide an indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads.
Process applications aim to provide a suitable environment for an industrial or a commercial process, regardless of internal heat loads and external weather conditions. Although often in the same comfort range, it is the requirements of the process that determines conditions, not human preference. Process applications include:
Other examples include:
In both comfort and process applications, the objective is not only to control temperature; (although in some comfort applications, this is all that is controlled) but also factors like humidity, air movement, and air quality.)
See the main article: Heat pump and refrigeration cycle |
In the refrigeration cycle, a pump transfers heat from a lower temperature source into a higher temperature heat sink. Heat will naturally flow in the opposite direction. This is the most common type of air conditioning. A refrigerated air conditioning system works in much the same way, pumping heat out of the room in which it stands.
This cycle takes advantage of the universal gas law PV = nRT, where P is pressure, V is volume, R is the universal gas constant, T is temperature, and n is the number of molecules of gas (1 mole = 6.022×1023 molecules).
The most common refrigeration cycle uses an electric motor to drive a compressor. In an automobile, the compressor is driven by a pulley on the engine's crankshaft, with both using electric motors for air circulation. Since evaporation occurs when heat is absorbed, and condensation occurs when heat is released, air conditioners are designed to use a compressor to cause pressure changes between two compartments, and actively pump a coolant around an enclosed system. They do this in a Condenser and a Evaporator The cooling liquid, or refrigerant is pumped into the cooled compartment (the evaporator coil). Low pressure then causes the refrigerant to evaporate taking the heat with it. In the other compartment (the condenser), the refrigerant vapor is compressed and forced through another heat exchange coil, condensed into a liquid which then rejects the heat previously absorbed from the cooled space.
Air conditioning has as much influence on human health as any generic heating system. Poorly maintained air-conditioning systems (especially large, centralized systems) can occasionally promote the growth and spread of microorganisms such as Legionella pneumophila, the infectious agent responsible for Legionnaire's disease.[2] Air conditioning can have a positive effect on sufferers of allergies and asthma.[3]
In serious heat waves, air conditioning can save the lives of the elderly. Some local authorities have even set up public cooling centers for the benefit of those without air conditioning at home.