Adiabatic cooling is the process of reducing heat through a change in air pressure caused by volume expansion.
In data centers and other facilities, adiabatic processes have enabled free cooling methods, which use freely available natural phenomena to regulate temperature. The principle of adiabatic cooling has been harnessed to develop cooling units that can save industry millions of liters of water. In the United States, older cooling towers currently use 1.5 quadrillion liters of water, which they tend to pollute. Adiabatic cooling units can also save more than 40% in electricity.
Adiabatic cooling is used in evaporative coolers. An evaporative cooler is basically a large fan that draws warm air through water-moistened pads. As the water in the pads evaporates, the air is chilled and pushed out to the room. The temperature can be controlled by adjusting the airflow of the cooler.
In nature, adiabatic cooling is often associated with elevation. As seen with cloud formations, an air mass that is heated expands and becomes less dense. Being less dense, it is lighter and rises above a higher-pressure air mass. Having reached areas with less dense air, it further expands, losing energy that was gained, and cooling as it does so. When the cooling air crosses the dew point, moisture in the air accumulates as clouds. With enough moisture and cooling comes precipitation. The principles of adiabatic cooling are also applied to increase humidity in facilities.
Conversely, adiabatic heating results when a cooler, less dense air mass sinks and increases in temperature due to the pressurized molecules becoming agitated, vibrating and increasing in heat.