Technical
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 MPT nozzles and connectors .
• 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
Air atomising humidification fogger .
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 .
An example of an air atomising nozzle .
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 . RACA
58
RACA Journal I March 2022 www . hvacronline . co . za