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How Does Air Conditioning Cool the Air?
Credit: Dreamstime

With the summer upon us, cooling off is becoming more and more important. While everyone enjoys the benefits of air conditioning, for many people, how the air is actually cooled is one of life's little mysteries.

There are two basic types of air conditioning, and they work in different ways. Perhaps the best-known type is refrigerated cooling. This is the type of air conditioning found in vehicles, office buildings and most homes, and it uses the same process that happens in a refrigerator. Refrigeration is best understood not as the process of making things colder, but instead moving heat from one place to another. Air conditioning units basically take heat energy out of the ambient air inside a home and release it outdoors.

The second type of air conditioning, evaporative cooling, is common in dry climates such as the American Southwest. Also known as a swamp cooler, this type of air conditioner cools outside air through the process of evaporation and blows it into the building.

Swamp coolers look like large boxes with grills on four sides. Each side has a panel with an evaporative pad, which usually contains plastic or organic materials like fine wood chips. Inside is a motor which pulls air from the outside, drawing it through the wet, sponge-like pads. The heat in the air is absorbed by the water in the pads and then the cooled, moist air is blown into the house. Because evaporation works best on air that is hot and dry, swamp coolers are only used in arid climates. The human body cools itself through perspiration using this same principle.

Each type of cooling has advantages and drawbacks. For example, refrigerated cooling creates colder air than swamp cooling, but is more expensive to run. Swamp cooling can require a lot of water,which is not plentiful in arid regions.

Fans do not cool air, but instead merely move it around. This can have a cooling effect on a person by carrying away body heat and increasing the rate of evaporation from sweaty skin, but does not decrease the ambient temperature of a room. In fact, fans generate a small amount of heat from the motor.