A swamp cooler cools air by evaporation
Q:
 What the heck is a swamp cooler and how does it work-Jack W., Washington D.C.
A: A swamp cooler (more formally called an evaporative cooler) is essentially a large box-like frame containing a big fan and
walled in by water-wetted pads, usually made of cedar shavings or cellulose. The fan whooshes the hot outside air through the
dripping pads (which are continually soaked by a water pump), cooling the air by about 20 ºF as the air evaporates water
molecules from the pads. The fan then blows the water-cooled air through the house and out a deliberate vent.
Right: [ASAP Heating & Cooling] Cut away photo of a swamp cooler
Wet the back of your hand -- then blow on it. Your skin surface feels cooler. That's evaporative cooling.
Folks differ on why it's called a swamp cooler. Some say because it makes the house feel like a muggy swamp-but that's only when the late summer rains
come and the cooler is less efficient. On dry days-which is almost every day in a desert-a swamp cooler works fine. In high humidity areas, like Washington
D.C., they don't work at all because the water does not evaporate appreciably and thus the air is not cooled.
Swamp coolers are popular in the southwest because they are relatively inexpensive, use a quarter as much electricity as a refrigerated unit, are easy to maintain
by the average do-it-yourselfer, and add a comfortable level of humidity to the dry desert air. The smell of fresh cedar pads on the first hot days of summer is
delightful.
(Answered by April Holladay, science correspondent, September 19, 2001)
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