Nozzle selection boils down to plume size.
Plume size is a function of nozzle size, system pressure, and relative humidity.
Nozzle sizes range from 0.08mm to 1.0mm. They could also be clasified as small medium or large. Small being 0.08mm, 0.10mm, and 0.15mm nozzles. Medium being 0.20mm - 0.50mm and large being 0.60mm - 1.0mm nozzles.
System pressure ranges from 150 psi through 1000 psi.
The smallest plume is about 3 feet using a 0.08mm or 0.10mm nozzle running with a system water pressure around 150 psi - with a low relative humidity. With a high relative humidity, say 70% and above the plum can become 6 feet ever with a small orifice nozzle.
The large plumes can become 20 to 30 feet, maybe more. This would be the larger nozzle running at high pressures, 800 through 1000 psi with higher than normal relative humidity levels.
Everything else falls in-between
What is the plume distance you need?
The majority of cooling and humidification application use small nozzles.
Humidification will use all three small nozzle sizes depending on ceiling height and humidity demands. High bay ceiling of 30 feet will use the 0.15mm, maybe 0.20mm nozzle. Lower bay ceilings will use the 0.08mm and 0.10mm. In some instances low bay ceiling applications will lower system water pressures to get the plume they desire.
Cooling applications will typically not use the real small nozzles. Mist output / cooling levels may not be good enough. A 0.20mm or 0.30mm nozzles should have the mist needed for sufficient cooling. Plume size does become larger reaching 5 to 8 feet.
What is your Misting Solution?
Your enviroment will determine your nozzle size.
How much room for evaporation do you have? Do you need?
Are you cooling or humidifying?
Or, are you in a wet application? Dust Control, Hydroponics, Green House Humidification.
Wet or Dry Application
Most misting solutions are dry applications, applications where the water has completely evaporated into the surrounding air. At this point the work is done. You have cooled the area and raised the relative humidity level at the same time.
Dry applications will typically use small orifice nozzles, 0.08mm, 0.10mm, or 0.15mm.
If you are looking at a wet application you job as a nozzle selector is much easier. Any nozzle can get thing wet. How wet? Well, that's up to you and the capacity of the nozzle. The closer the nozzle is to the product the more wet it gets.
Nozzle plume distance to your object.
Nozzle selection is a function of nozzle distance to the object being conditioned.
In other words, key factors in evporation rate are, nozzle size, pump pressure, surrounding relative humidity.
To a degree all nozzles can be used in all applications. In a dry application we are typically looking at the small orifice nozzles, 0.08mm, 0.10mm, and 0.15mm. These nozzles produce the smallest water particle size (droplet size) for quick evaporation.
Larger orifice nozzles need larger area for complete evaporation. With some larger nozzles complete evaporations is just about impossible. We can conclude then that larger nozzles are typically a wet application nozzle.
Plume Angle, Cone Size
Plume Size is determined by design, nozzle capacity, and pump pressure. Small nozzles have a narrow angle plume, 30 degrees. Larger nozzles have a wider angle plume, up to 80 degrees. Wider angle higher capacity spreads out the water to assist the evaporation process. Nozzles have design operating range pressure. Plume is properly formed at design pressures.
Water Droplet Size
Droplet Size is optimized at design pressures, optimized meaning highest concentration of smallest water particles. Larger water particles at lower nozzle pressures is an operational trade off.
Some nozzles come with filter built in. I prefer this type. However I also insist on a system filter. Then, if you are having trouble with a nozzle, spray pattern, output, etc. you know the orifice is clean and you nozzle filter is clean, it should be something else.
Pressure, variable pressure can work to your advantage. Variable pressure mean variable plume size, plume control. Operating a nozzle outside its design pressure can work to your advantage.
Nozzle Check Valve
Some nozzles have a build in check valve. This valve is used to prevent dripping on the off cycle. When a check valve is used generally there is a system dump valve also. This dump valve opens on an off cycle to relieve system high pressure. This lets the check valve shut quickly thus avoiding dripping.
Pick a good nozzle that has the features and options needed. All to asssist in trouble free opeartion.
If you are doing lite misting for humidification or close proximity cooling and would like additional filtration here are some (ebay) options.
If the additonal filtering is not needed but quality is important here are some alternates.