Evaporative cooling towers, closed circuit fluid coolers and evaporative condensers use the evaporation of a small volume of the recirculated water within a system to remove heat. A good example of this is the cooling effect you feel when air blows across your damp skin. The water evaporating from your skin removes some of your body’s heat and you feel cooler as a result. This same process allows evaporative cooling equipment to cool below the ambient dry air temperature and is a long-term renewable process as long as water is available.
Air-cooled equipment, as opposed to evaporative cooling, cools a fluid moving through a coil (with fins) by blowing air across the coil surface. The California Energy Commission limits the exclusive use of air-cooled equipment for HVAC applications to 300 tons. Water-cooled chillers with evaporative cooling are required above that limit, with a maximum of 100 tons of dry cooling per installation, typical for special purposes. For example, on a 900 ton system, 800 tons are required to be evaporative, with 100 tons dry permitted. The energy savings are significant, depending on the local weather, but are usually more than a 5 to 1 reduction over air-cooled equipment. If water resources are not an issue, evaporative cooling is always the lowest cost and most energy efficient solution.
Cooling towers originally came into use to avoid the once-through use of water from lakes and rivers, instead using a recirculated closed loop system to cool the warm water before returning it to the process. Enormous amounts of water have been saved through the use of cooling towers.
Where large quantities of water are unavailable or restricted, air-cooled or hybrid combinations of evaporative and air-cooled equipment can be applied to reduce or eliminate water consumption. Hybrid evaporative cooling equipment utilizes a combination of wet and dry components that enable maximum cooling efficiency at high heat load conditions and maximum water savings at reduced load — the best of both worlds.
Evaporative cooling is an environmentally friendly process using naturally replenished water to enhance cooling. In fact, evaporative cooling provides 95+ percent effectiveness in cleaning, or scrubbing, the air that flows through the tower.