How Do Misting Fans Work?
If you’ve ever been at the beach on a hot day, have you found that being near the waters edge, even if you don’t go in, feels cooler?
The reason for this is that water at the shore is heavy with moisture from the sea and as the moisture evaporates it uses the energy from the sun that would otherwise be heating you. The process of evaporation draws energy from the surrounding environment making it feel cooler. They DO work. If set up correctly they can cool the air temperature noticeably sometimes by as much as 30F.
In very simple terms, this is how misting fans work.
What Do Misting Fans Do?
Misting fans comprise a powerful fan combined with a high pressure water pump that is connected up to a water supply.
When operating, the pump squirts out water at very high pressure through a tiny nozzle. Anyone who has covered the end of a hose with their fingers knows that if you get your fingers in the right position the water from the hose sprays out instead of pouring out. This is the same principle.
The spray from the pump is directed into the path of the fan and gets circulated around the area surrounding the fan. The heat from the sun then evaporates the air cooling the air temperature in the area. In order to get the maximum cooling effect the best misting fans oscillate, meaning they move back and forth ensuring the mist is spread is as large an area as possible.
Misting Fan Droplet Size
The size of the spray droplets is very important. If the droplets are too large then instead of evaporating in the air, they will quickly fall to the ground wetting anything in their path. Instead of making an area cooler the result will only be that everything in the area becomes slickly wet and a bit unpleasant to touch.
If the droplets are the right size, as small as possible, they will “flash evaporate” in the hot air and cool the surrounding area quickly before the droplets fall to the ground and cause wetness.
The size of the mist droplets is determined by two factors, the size of the nozzle through which the water is pumped, and the power of the pump itself. There are a number of patio misting fans on the market which connect up to water direct from the faucet, but unless these have an integrated high pressure pump, they are unlikely to work well.
In simple terms the lower the pressure from your pump the smaller the nozzle size should be.
Where Do Misting Fans Get Their Water From?
The water may be supplied directly from a hose or can be in the form of a reservoir attached to the base of the fan. It really depends upon your particular misting fan, your preference and whether you have a hose available
How Much Water Do Misting Fans Use?
This really depends upon the size of the misting fan, the power of the pump, the width of the nozzle through which the water is pumped and of course the number of nozzles used.
Commercial misting fans with large high pressure pumps can consume quite a lot of water, whereas small domestic misting fans are obviously more conservative.
With a 1000 psi high pressure pump, and a .008" nozzle size you can use a mist nozzle flow chart (see below) to calculate the water used.
In the example above our 0.008” nozzle at 1000 psi would create a droplet size of 6 microns and use 1.89 gallons of water per hour.
Are Misting Fans Safe?
Any combination of water and electricity needs to be treated with respect. You should make sure that your fan is certified as complying with regulations.
In addition you should check that your fan has a built in ground fault circuit interrupter (GCFI) which should shut off power immediately if there is any problems with the electrical circuit.
In addition, when in operation you should make sure you monitor the air temperature regularly to ensure that evaporation continues to occur. In the event that the air temperature cools so that no evaporation takes place then the floor and other surfaces can become wet and slippery.
Can Misting Fans Be Used Indoors?
Misting fans require hot air to evaporate the water droplets created. If the air is not sufficiently hot then the droplets may not evaporate before the fall out of the air and make anything on the floor and the floor itself wet.
For this reason, misting fans work best outdoors, in fact they work best in full sunlight rather than shaded areas for the same reasons.
Can they be used indoors? The answer is yes they can but with caution. And when in use their effect should be closely monitored to ensure that if temperatures cool to the point where evaporation is no longer occurring they should be switched off immediately.
If you do use a misting fan indoors it is best to use it in a well ventilated room and try to position the fan so that the spray area goes with the direction of air flow and not against.