Evaporative cooling: How it works and why it saves you money

Author: Gary Jouas –
Evaporative cooling is actually a complicated phenomenon dependent upon air and water temperature, air-flow and humidity or the amount of water that already exists in the air. Although the physics behind this phenomenon are complex, it can be explained simply in laymen terms.

On an afternoon where it is 80°F and dry, a slight breeze can give you a chill; however on that same 80°F day, that same breeze will offer little relief if the conditions are humid. This has everything to do the ability of the air to accept the moisture that your body is producing through perspiration. On the dry day, the air can easily accept the water your body generates hence cooling you through evaporation. Similarly, on the humid day, there is not enough room in the air to evaporate all of the additional water; hence it remains on the surface of your skin making you feel damp and clammy. Anything but cool!

Evaporative cooling can work almost anywhere, however it is most common and most efficient in dry climates for the reason stated above. Evaporative cooling was very popular in the Early American Southwest, when people would dip shear drapes in water and hang them in front of an open window. The warm dry desert breeze would blow through the open windows, filter through the damp drapes and drop the air temperature to cool the space within the home. This same concept was employed in various inventions to move air through an evaporative cooling media and force the air into the living space. However the laws of physics still applied and hot humid conditions would prove a challenge. Eventually, the introduction of refrigerated air opened up booming industry that could provide adequate cooling regardless of the outdoor environment. Unfortunately, this technology came (and still comes) with a cost. The cost of the refrigeration equipment is a multiple of the cost of an evaporative cooling counterpart. The cost of running a compressor and air handler can also be a multiple of the low cost of running an evaporative cooling system.

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