Micro-fine droplet systems are used in a range of applications that require sprayed water to evaporate before wetting the surroundings, resulting in evaporative cooling or humidification.
Evaporative cooling occurs when water evaporates and energy, or heat, in the air dissolves the droplets, effectively removing some of the heat and resulting in cooling of the air. An example of the effect of cooling by evaporation is when restaurants use 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 customers and the air temperature drops significantly, resulting in further cooling.
The same principle is used in chicken runs, to ensure that air temperature does not reach dangerously high levels. Evaporative cooling is also used in various sporting events, such as the Comrades marathon and Argus cycle race, where mist-cooling tunnels help to cool participants without wetting their running shoes or bicycles.
Water evaporation also helps to increase the amount of humidity in the air, which is an important factor in a number of applications. Increases in humidity surrounding day-old chicks has been shown to improve the ratio of food consumption to weight gain in adult chickens, allowing the slaughter weight to be reached earlier.
Timber drying sheds at sawmills also require careful humidity control to prevent logs from cracking. Humidity in textile weaving sheds helps to avoid static electricity build-up, which can cause threads to snap.
Manufacturer of industrial high-pressure pumping and cleaning equipment, Monitor Distributors, trading as Hawk Pumps, provides a range of spraying solutions, including industrial nozzles and is able to custom design and manufacture solutions tailored to specific requirements.
Two methods are commonly used to create micro-fine droplets, namely high pressure atomisation and compressed air atomisation and specific nozzles are required for both these methods.
High pressure atomisation commonly requires small threaded nozzles, about 8 mm in diameter, 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 0.02 mm in diameter and the pressure is pumped at 40 bar to 60 bar. Because the orifices are so small, very well filtered, soft water is required.
The air atomising method requires water to be fed into a nozzle block, often with four nozzles pointed in four directions, and water is then atomised by compressed air. This is more suited to textile mills where nozzles would be placed throughout the treatment area. These types of nozzles can also be remotely activated for production line applications.
Specialised air atomising nozzles can be used in bakery proofing rooms, where ultra fine droplets are sprayed in all directions, adding moisture to the air and ensuring that the dough does not dry on the surface, causing the bread to split when baked.
Hawk Pumps asserts that using the correct nozzle for a specific application ensures an effective solution for any evaporative cooling and humidification requirements.