Evaporative cooling - Chapter 19 of your 1996 HVAC Systems and Equipment ASHRAE Handbook covers evaporative cooling. The basic concept is pretty simple - a spray of water into an airstream causes the temperature to drop, due to the evaporation of the water. Unfortunately it also makes the airstream more humid. Evap coolers (or swamp coolers as they are sometime called) are used all over the southwest. They work best in hot dry climates. The major drawback is that they cannot drop the air temperature below the wet-bulb temperature, so on a humid day they don't do much. But they can be combined with conventional systems to reduce loads, especially in systems with high ventilation requirements, like for places of assembly or labs.
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