Anyone who has attended a large outdoor event or watched the sidelines during a televised football game has most likely seen a misting fan in action. Sometimes this type of fan is surrounded by open canvas flaps and promoted as a chill zone. The air around these fans can be up to 40° Fahrenheit cooler than the ambient temperature, turning an unpleasant 100°F (38°C) workday into a very tolerable 75°F (24°C) within minutes of operation.
When used in a closed environment such as a greenhouse, a misting fan initially cools the general area, then provides a high degree of humidity for thirstier plant species. Some specialty produce stores may also use these types of fans to keep their offerings fresh for customers. The air-conditioning effects can also make for a more pleasant shopping environment for outdoor produce stands.
A typical misting fan works on the principles of thermal dynamics and evaporative cooling. If you place a wet towel in front of an electric fan, you may notice the area around the towel becomes noticeably cooler. As the water from the towel evaporates, it takes a certain amount of heat energy along with it. The fan circulates the cooler air around the room, acting like a rudimentary air conditioner. Misting technology takes this idea of evaporative cooling and makes it much more efficient and productive.
It all begins with the water. Special high-pressure pumps generate enough water pressure to reach a rating of 1000 PSI (pounds per square inch). Extremely fine nozzle openings reduce the outbound water to micron-sized droplets. This action creates a thin mist which evaporates almost immediately upon contact with the warm ambient air and sunlight. As the individual droplets pull heat energy along with them, the air temperature can drop significantly. An electric fan blows this supercooled air and mist combination for several hundred yards or more.
Because the mist created by a misting fan system is so fine, few beneficiaries of this cooling effect actually become wet. The effect is similar to standing in a light fog on cool mornings — the water vapor may condense on cold surfaces, but will barely register on human skin. Only those standing less than 6 inches (15 cm) away from the water nozzle may experience significant wetness. The water supply of the fan is usually filtered for impurities before entering the nozzle, and the total amount of water used is rarely more than 1 or 2 US gallons (about 3.8 to 7.6 liters) per hour.
Although most misting fan systems are used to cool crowds of people in outdoor arenas or stadiums, smaller units for home use have become more popular. Some outdoor pool owners find it more comfortable for swimmers if the area around the pool is kept cool as well. Those who like to work in backyard gardens or outdoor garages may also benefit from the cooling effects of this type of fan. Mowing a small yard doesn't have to involve long, hot stretches on a riding mower anymore. These home misting fan systems don't require special equipment, since the built-in water pumps and nozzles are already calibrated for maximum performance.