How Does an Evaporative Cooler Work?

Simple and Effective

Evaporative coolers, also sometimes referred to as swamp coolers, are used to cool homes and businesses in areas that have hot, dry climates. The simple design of these coolers makes them both affordable and reliable.

Design

These enclosed units are square or rectangular in shape with the bottom of the unit serving as a shallow water reservoir. The water supply coming into the unit is brought via plastic or copper tubing that runs from the existing plumbing of the structure being cooled. The water flow is regulated by a simple float valve, similar in type to that found in toilet tanks. A pump pulls water from the reservoir and pumps it through tubing up to the top of the unit, where it continually flows down the sides and through pads that line the sides of the unit. An electric motor powers a fan in the center of the cooler. The fan serves two functions; to draw outside air through the pads and into the unit, and to force this now cooler air out through the exit duct and into the area to be cooled.

Physics

As the warm air is drawn in through the porous pads, the heat in the air causes the water flowing through these pads to evaporate. This evaporation is caused by a transfer of heat from the air to the water. This results in a net loss of heat in the air---or in other words, cooling. The efficiency of this process decreases as the percentage of humidity in the outside air increases, explaining why evaporative coolers are not used in humid climates.

Resources

• History, Benefits and Drawbacks of Evaporative Coolers