Misting Nozzles Explained

 

Why so many misting nozzles?

Misting nozzles come in a variety of shapes and sizes. It is often asked,’Why so many and what are the differences?’. The purpose of this blog is to answer these questions and define the performance capabilities of the impeller misting nozzles offered by Fogco.

Impingement versus Impellar

There are two basic types of misting nozzles, impingement nozzles and impellar nozzles. Impingement nozzles allow water to exit the nozzle in a straight stream through a very small orifice (typically .008″ or about 200μ or microns) and immediately collide with a solid pin which effectively atomizes the water into tiny droplets, usually between 1μ and 15μ. Impingement nozzles tend to be very expensive; it is hard to maintain the position of the solid pin and therefore hard to maintain their performance; and they are typically used in speciality applications. For these reasons, they will not be further defined in this blog post. For more information on impingement nozzles, contact Fogco Customer Service.

Impellar nozzles are the most common misting nozzle and they have been used in the mist and fog industry for over 50 years. They are much less expensive than impingement nozzles and they are more reliable. The downside of this mist nozzle design is that it cannot consistently produce as fine a droplet as an impingement nozzle. For the vast majority of applications, this is not an issue which is the primary reason why impellar nozzles are so widely used. A well designed and machined impellar style nozzle will provide droplets ranging from a few microns up to about 50μ with the majority of the droplets being larger than 10μ.

Although there have been improvements to impellar misting nozzles over the last 20 years, the basic performance and function has not changed. Essentially, the impellar style nozzles are designed to atomize the water flow into tiny droplets. These nozzles utilize a barrel shaped impellar, a small orifice, and a vortex shaped interior to force the water through the nozzle in such a way that it explodes through the small opening in a circular motion resulting in billions of tiny individual droplets.

When placed in a series along a length of tubing or onto the facing of a fan, the water is absorbed by the air and evaporative cooling takes place. If the nozzles are placed in an enclosed area, increased humidity levels are achieved. These nozzles are available in brass and stainless steel or in an all stainless steel design. They are also available with standard orifice sizes from .006″/.015mm to .020″/.5mm. Larger orifice sizes are also available as special order.

Standard mist nozzles versus Cleanable mist nozzles

There are two basic types of impellar nozzles, cleanable and non-cleanable. The cleanable mist nozzle refers to a nozzle design that allows the barrel shaped impellar to be removed from the body of the nozzle allowing for the easy removal of foreign debris as well as the ability for cleaning solution to flush the interor of the nozzle and remove any dissolved solids that may plug up the orifice. In 95% of the cases, a poor spraying or plugged nozzle can be dis-assembled and cleaned returning the nozzle to its original performance capability.

The cleanable nozzles also include an anti drip assembly inserted into the body of the nozzle. This assembly prevents the misting nozzle from dripping each time the system is turned off. In some applications this is not that important, but if preventing the nozzle from dripping is important, the anti drip assembly is crucial. The anti drip assembly can be removed from the nozzle if it is not required.

The standard non-cleanable nozzles are less expensive but they cannot be as readily cleaned as the cleanable design. The success rate for improving a plugged or poor spraying non-cleanable nozzle is about 50%. In most cases, the overall investment of the entire misting system justifies the extra cost of the cleanable nozzles. They usually pay for themselves within the first year.

The Nozzle Page and the Fogco Product Catalog provide specific information on the available misting nozzles, but the additional details below may be helpful in deciding which orifice size is best for a specific applicaton.

The .006″/.15mm nozzle (YELLOW o-ring) is the smallest standard nozzle orifice available. At 1,000 psi, the mean diameter of the droplets from this size orifice are 12.2μ with droplets ranging from 1.2μ to 36.4μ with a spray diameter of approximately 45 degrees. The .006″/.15mm misting nozzle is ideal for applications requiring extremely low flow with small droplet size and minimal moisture. It is most commonly used for humidification applications. This nozzle is not designed to be used at pressures below 500 psi.

The .008″/.20mm nozzle (RED o-ring) is the next smallest standard nozzle orifice available. At 1,000 psi, the mean diameter of the droplets from this size orifice are 12.7μ with droplets ranging from 1.4μ to 37.9μ with a spray diameter of between 60 degrees and 65 degrees. The .008″/.20mm misting nozzle is ideal for applications requiring low flow with small droplet size and limited moisture. It is most commonly used for humidification and cooling applications. This nozzle is not designed to be used at pressures below 250 psi.

The .012″/.30mm nozzle (BLACK o-ring) is the medium sized standard nozzle orifice. At 1,000 psi, the mean diameter of the droplets from this size orifice are 13.1μ with droplets ranging from 1.6μ to 39.1μ with a spray diameter of between 65 degrees and 75 degrees. The .012″/.30mm misting nozzle is ideal for applications requiring moderate flow with small droplet size. It has a similar performance to the .008″/.20mm orifice nozzle with an increased flow rate. It is most commonly used for outdoor cooling odor/dust control applications. This nozzle can be used with any pressures above 100 psi.

The .016″/.40mm nozzle (BROWN o-ring) is a larger sized nozzle orifice. At 1,000 psi, the mean diameter of the droplets from this size orifice are 14.8μ with droplets ranging from 3.8μ to 47.9μ with a spray diameter of between 70 degrees and 80 degrees. The .016″/.40mm misting nozzle is ideal for applications requiring increased flow rates with moderately sized droplets. It is most commonly used for special effects and outdoor dust control applications. This nozzle can be used with any pressure.

The .020″/.50mm nozzle (GREEN o-ring) is a largest sized standard nozzle orifice. At 1,000 psi, the mean diameter of the droplets from this size orifice are 15.2μ with droplets ranging from 9.5μ to 49.9μ with a spray diameter of between 80 degrees and 90 degrees. The .020″/.50mm misting nozzle is ideal for applications requiring extreme flow with larger droplets where complete evaporation is not required. It is most commonly used for outdoor dust control in demolition applications. This nozzle can be used with any pressure.