Adiabatic cooling
Also known as: adiabatic pre-cooling, adiabatic condenser, evaporative pre-cooling
Short definitionCooling the air entering a condenser or gas cooler beforehand with a wetted pad or a water mist. Water is turned on only in the hot hours; in return the condensing temperature is pulled down.
As water evaporates it cools and humidifies the air. A cellulose pad is fitted on the intake face of the coil, or nozzles giving a fine mist are lined up there, so the air reaching the fins is cooler than the air outside. The lower limit is the wet-bulb temperature, and a pad system gains 70–90% of the difference between dry bulb and wet bulb. With a pad the coil does not get wet; that is also what sets it apart from a tower.
The gain depends on climate. In a hot, dry region such as Central Anatolia condensing can drop by 10–12 K, while on a humid coast you settle for 3–5 K. In most installations water is turned on once the outdoor temperature passes 25–28 °C, so the amount used over a year stays small beside a tower. In mist types where the water lands directly on the fins, softening or reverse osmosis is needed; otherwise scale coats the coil within a few summers. The pad’s resistance goes into the fan calculation, because the pad restricts the air even when dry.