Air Conditioning Basics

Air-conditioning Basics
An air conditioner is basically a refrigerator without the insulated box. It uses the evaporation of a refrigerant, like Freon, to provide cooling. The mechanics of the Freon evaporation cycle are the same in a refrigerator as in an air conditioner. According to the Merriam-Webster Dictionary Online, the term Freon is generically "used for any of various nonflammable fluorocarbons used as refrigerants and as propellants for aerosols."

The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (red in the diagram above).
This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.
The Freon liquid runs through an expansion valve, and in the process it evaporates to become cold, low-pressure Freon gas (light blue in the diagram above).
This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.
Mixed in with the Freon is a small amount of a lightweight oil. This oil lubricates the compressor.