For general aspects of air conditioning, see Air conditioning.

An air conditioner is an appliance, system, or mechanism designed to extract heat from an area using a refrigeration cycle. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC. Its purpose, in the home or in the car, is to provide comfort during hot weather.

Contents [hide] 1 History 2 Air conditioning applications 3 Air conditioning system basics and theories 3.1 Refrigeration cycle 3.1.1 Humidity 3.1.2 Refrigerants 4 Types of air conditioner equipment 4.1 Window and through-wall units 4.2 Evaporative coolers 4.3 Absorptive chillers 4.4 Central air conditioning 5 Thermostats 6 Equipment capacity 6.1 Seasonal Energy Efficiency Rating (SEER) 7 Insulation 8 Home air conditioning systems around the world 9 Health implications 10 References 11 See also 12 External links 12.1 Energy efficiency

[edit] History

Main article: Air conditioning#History

[edit] Air conditioning applications

Main article: Air conditioning#Air conditioning applications

[edit] Air conditioning system basics and theories

[edit] Refrigeration cycle

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor.

In the refrigeration cycle, a heat pump transfers heat from a lower temperature heat source into a higher temperature heat sink. Heat would naturally flow in the opposite direction. This is the most common type of air conditioning. A refrigerator works in much the same way, as it pumps the heat out of the interior into 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 moles 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 belt over a pulley, the belt being driven by the engine's crankshaft (similar to the driving of the pulleys for the alternator, power steering, etc.). Whether in a car or the house, both use electric fan 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 condense and pump a refrigerant around. A refrigerant is pumped into the cooled compartment (the evaporator coil), where the low pressure and low temperature cause the refrigerant to evaporate into a vapor, taking heat with it. In the other compartment (the condenser), the refrigerant vapor is compressed and forced through another heat exchange coil, condensing into a liquid, rejecting the heat previously absorbed from the cooled space.