A Simple Explanation of How Evaporative Cooling Works

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When you walk along the beach in San Diego and feel a cool breeze coming off the water, this is a great example of evaporative cooling. However, if you go inland 50 miles, you will feel a very real difference because of the high dry bulb temperature with no evaporation taking place. Evaporative cooling takes place when warmer air comes into contact with cooler water, causing the water to evaporate into the air and thus have a cooling effect on the air.

This adiabatic process works by taking advantage of differences between the dry bulb temperature (dbt) and the wet bulb temperature (wbt). This differential is known as the wet bulb depression (wbd). The greater the wet bulb depression, the greater the felt effect is on the discharge air temperature. In ideal operating conditions, evaporative cooling systems are typically able to lower the sensible heat of the air by 80-90 percent of the wet bulb depression.

Once the outside air passes through the evaporative medium, it provides cool air that can now be moved through the facility, thus removing heat, and then be vented out, providing a continuous stream of fresh air.*

*Taken from The Green Solution for Big Box Cooling

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