Evaporative cooling is a process that reduces air temperature
by evaporation of water into the airstream. As water
evaporates, energy is lost from the air causing its temperature
to drop. Two temperatures are important when dealing
with evaporative cooling systems – dry bulb temperature
and wet bulb temperature. Dry bulb temperature is the
temperature that we usually think of as air temperature.
It is the temperature measured by a regular thermometer
exposed to the airstream. Wet bulb temperature is the
lowest temperature that can be reached by the evaporation
of water only. It is the temperature you feel when your
skin is wet and is exposed to moving air. Unlike dry bulb
temperature, wet bulb temperature is an indication of the
amount of moisture in the air.