How Air Conditioning Really Works

­When the temperature outside begins to climb, many people seek the cool comfort of indoor ai­r conditioning. Like water towers and power lines, air conditioners are one of those things that we see every day but seldom pay much attention to. wouldn't it be nice to know how these indispensable machines work their magic?

Air conditioners come in various sizes, cooling capacities and prices. One type that we see all the time is the window air conditioner, an easy and economical way to cool a small area. People who live in suburban areas usually have a condenser unit in the backyard. If you live in an apartment complex, you'll probably see multiple condensers for each dwelling. Most businesses and office buildings have condensing units on their roofs, and as you fly into any airport you notice that warehouses and malls may have 10 or 20 condensing units hidden on their roofs. At office complexes, you'll find large cooling towers that are connected to the air conditioning system.

Even though each of these machines has a pretty distinct look, they all work on the same principles.
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Lets’ examine air conditioners -- from small to huge -- so you know more about what you're seeing. We'll also look at some new, energy-efficient cooling methods.

Air Conditioning Basics
Most people think that air conditioners lower the temperature in their homes simply by pumping cool air in. What's really happening is the warm air from your house is being removed and cycled back in as cooler air. This cycle continues until your thermostat reaches the desired temperature.

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-website Dictionary Online, the term Freon is generically "used for any of various nonflammable fluorocarbons used as refrigerants and as propellants for aerosols."
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Diagram of a typical air conditioner

This is how the evaporation cycle in an air conditioner:

1. The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (red in the diagram above).

2. This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.

3. 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).

4. 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 lightweight oil. This oil lubricates the compressor.

Air conditioners help clean your home's air as well. Most indoor units have filters that catch dust, pollen, mold spores and other allergens as well as smoke and everyday dirt found in the air. Most air conditioners also function as dehumidifiers. They take excess water from the air and use it to help cool the unit before getting rid of the water through a hose to the outside. Other units use the condensed moisture to improve efficiency by routing the cooled water back into the system to be reused.

So this is the general concept involved in air conditioning.