ANYONE who uses high-pressure pumping equipment for professional purposes knows that every nozzle is different. The experts at Hawk Pumps explain some of the benefits of evaporative cooling and humidification spray nozzles.
There are many situations where micro-fine water droplets are necessary. Generally, micro-fine droplets come into play for applications that require the water sprayed to evaporate before wetting the surroundings. This method serves two purposes – evaporative cooling and humidification.
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 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. In some areas, the high air temperature can kill the birds and evaporative cooling saves them.
In numerous Comrades Marathons and Argus Cycle Races, mist-cooling tunnels were provided by Hawk pumps for the participants. It was important that the mist was fine enough to cool the air and the competitors without wetting them. Their shoes (for the runners) or their bikes (for the cyclists) could not be wet. These were very successful projects.
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.
Some decades ago, Hawk was involved in experiments 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.
Humidification nozzles were used in a warehouse storing polystyrene. This was done to keep static electricity under control, reducing the risk of fires.
When it comes to using 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.
An example of connectors with an MPT Nozzle used in an Evaporative Cooling System
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.