History of Evaporative Cooling

     Evaporative cooling operates by harnessing the evaporation of water. The technology is primarily used in regions with low humidity. The technique works by passing air over pads that are saturated with water, which results in the evaporation of water from the pads into the forced air. Temperature reductions of 15 to 40 degrees Fahrenheit can be obtained this way. The air is directed into a building, forcing warmer air out the windows.

Ancient Technology

Fresco paintings from ancient Egypt depict slaves waving fans over containers of water. This appears to be the earliest recorded use of evaporative cooling. Wealthy citizens of Rome during the Roman Empire had water circulated through their walls. The common people hung wet mats over their doors for cooling.

Other Early Applications

Cooling towers were constructed in medieval times. The towers were designed to trap wind and funnel it past water before it entered a building. This method is believed have to have been developed in Persia. Water evaporative cooling was used in New England textile mills during the 1800s.

Willis Havillard Carrier

Willis Carrier was born in 1875 on a small farm in Angola, New York. Carrier’s mother taught math and problem-solving skills to her son. Carrier graduated from Cornell University with a master’s degree in engineering. From there, Carrier went to work at Buffalo Forge Co., which manufactured heaters, air exhausts and blowers. Carrier was appointed head of the company’s experimental science department.

Apparatus for Treating Air

Carrier was assigned the task of controlling the humidity in a Brooklyn printing plant.

Carrier gained an understanding of the relationship between the dew point, humidity and temperature while waiting for a train one evening. The young engineer designed a system that controlled temperature and humidity.

Southwestern United States

Residents of the U.S. Southwest tried various methods to combat summer heat. In the 1920s and 1930s, people hung wet sheets to capitalize on the evaporation process. Others risked pneumonia by sleeping in wet sheets with electric fans blowing on them.

Swamp Coolers

Several designs of evaporative cooling devices were tested in the Southwest. Until the 1960s, the swamp cooler was predominant. The swamp cooler used aspen pads to contain the water for evaporation. A swamp cooler was demonstrated in Phoenix at the Adams Hotel in 1916. Two professors at the University of Arizona experimented with methods to improve performance in evaporative coolers, and in 1939, they published instructions for cooling homes in Arizona.

swamp cooler

Recent History

Around the time of the professors’ instructions, the Emerson Company began mass production of evaporative coolers. Other companies soon entered the market. By 1939, drip coolers were being used at businesses and homes throughout the Southwest. Many companies were manufacturing evaporative coolers by the 1950s, and the market had expanded to include other parts of the United States, Canada and Australia. Advances continued on the technology. Improved pads reduced some issues such as the amount of power needed to push the air. However, the newer pads created the need to use recirculating systems to wet the pads. This in turn led to problems that affected unit size and location. Use of units that do not recirculate is one possible solution, but this increases water consumption.