AT-84-03-1 -- Indirect Evaporative Air Coolers for Hot, Dry Climates PDF

Evaporation of water into flowing airstreams has been used for many years to lower the dry-bulb temperature of the airstream. The drawback to this very simple process is the addition of moisture which it entails. Nearly 70 years ago, before there was much knowledge of psychrometric theory (Carrier’s classic paper was not published until 1911), the cooling tower was already in wide use. A large number of ingenious engineers sought ways to use the cooled water to reduce indoor air temperatures during the torrid and arid summers which characterize the climate of most of the desert regions of the world. Since practice preceded theory, as it has in so many aspects of engineering, this paper will first describe some of the early attempts to use evaporative air cooling. A brief excursion into psychrometric theory will be followed by a discussion of modern developments which have overcome many of the difficulties which beset the pioneers in this field.