The cooling mechanism
Direct evaporative cooling passes incoming air over wet media. Evaporation lowers its dry-bulb temperature and raises moisture content. The available temperature drop shrinks when outside air is already humid.
Ventilation is part of the design
Fresh air must enter and an approximately equal quantity of indoor air must leave. A tightly closed room will not behave like a conventional refrigerant air conditioner. Water supply and mineral buildup also deserve attention.
Different configurations
Window and portable units serve limited areas. A whole-building system needs distribution and exhaust planning. Indirect and two-stage systems use different air paths and should not be described as identical to basic direct coolers.
Before buying
Check local climate data, the product airflow rating, water consumption, installation opening, electrical supply and pad-cleaning needs. Compare comfort expectations against a conventional AC where humid days are common.
Sources and further reading
- US Department of Energy: Heat Pump Systems
- US Department of Energy: Central Air Conditioners and Heat Pumps