By Monitor Distributors T/A Hawk Pumps

Anyone who uses high-pressure pumping equipment for professional purposes knows that every nozzle is different.

For those in the know who would like to know even more, in this article experts highlight some of the benefits of evaporative cooling and humidification spray nozzles.

There are many applications where micro-fine water droplets are required. Generally, micro-fine droplets come into play for applications that need any water spray to evaporate before wetting the surroundings. This method serves two purposes – evaporative cooling and humidification.

Humidification nozzles used in a warehouse storing polystyrene. This was done to keep static electricity under control, reducing the risk of fires. Image credit: Hawk Pumps

Evaporative cooling

When water evaporates, energy in the air (heat) dissolves the droplets, effectively removing some of the heat and resulting in cooling of the air. It’s a bit like when a dog or a chicken pants when it is hot and the air flow evaporates their saliva, counteractively cooling the animal internally.

A typical example of the effect of cooling by evaporation is where a restaurant has rows of nozzles on pipes with a high-pressure pump forcing water through extremely fine jets. The droplets are so small that the water evaporates completely before reaching the customers, but the air temperature drops significantly, cooling the customers down as they walk through the spray.

The same principle is used in chicken runs as another example. In some areas, the high air temperature can kill the birds and evaporative cooling saves them.


Water evaporation will obviously increase the amount of water dissolved in the air (humidity), and there are many examples where an increase in humidity, is an asset.

Experiments have been conducted where increases in the humidity surrounding day-old chicks effectively improved the ratio of food consumption to weight gain of adult chickens, allowing the slaughter weight to be reached earlier.

Timber drying sheds at sawmills require careful humidity control to stop logs cracking.

Textile weaving sheds need humidity to avoid static electricity build-up, which causes threads to snap.

{os-gal-258} Images credit: Hawk Pumps

Nozzles for cooling and humidity control

Two methods are commonly used to create micro-fine droplets. High pressure atomisation and compressed air atomisation.

  • High Pressure Atomising
    The most common nozzles are small (+/- 8mm diameter) threaded ones, which either screw onto special tees connecting lengths of 3/8” plastic tubes, or into stainless steel pipes with threaded holes. The orifice size is approximately 0.02mm in diameter and the pressure is pumped at 40-60bar. Because the orifices are so small, very well filtered soft water is required.
  • Air atomising
    This method requires water to be fed into a nozzle block (often with four nozzles pointed in four directions) and atomised by compressed air. This is more suited to textile mills where the nozzles would be placed throughout the area being treated. Versions of these nozzles can also be remotely activated for production line applications.
        An atomising nozzle is used in the proofing rooms in bakeries. It sprays ultra-fine droplets in all directions, adding moisture to the air. The purpose of keeping the air moist during the proofing process is so that the dough does not dry on the surface, causing the bread to split when baked. While this is a specialised nozzle, standard air atomising nozzles can be used for this process.

As you can see, there is more to evaporative cooling and evaporation techniques than meets the eye. And ensuring you have the right nozzle can have positive – or even life-changing – effects, depending on the application.

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