Nortec AIRFOG Series - Manual (Page 6)

2 | AirFog Installation Manual
water distribution pipes. Increases in air velocity (by increasing air pressure) will increase the
vacuum pressure and increase the rate that water is siphoned into the nozzle. As the water
exits the nozzle it is broken down into a fine mist by a shearing action created by the
compressed air. Increases in air supply pressure also means that the exiting mixed flow is at
a higher velocity.
Since AFE nozzle systems use a zero psig water pressure feed network, the water feed
system and nozzles at the same height as the water pressure reduction regulator (vacuum
valve). Valleys or peaks in altitude will adversely affect performance and in some cases will
prevent the nozzles from producing any output. If obstructions prevent straight level piping,
the water and air network delivery pipes must be routed under the obstruction. It is vital that
the water pipes, downstream of the vacuum valve, never be elevated higher than the
nozzles.
General AirFog Technical Considerations
Adiabatic Cooling Phenomena
There are no heating elements in any of Nortec’s AirFog humidifiers. Water is injected directly
into the air at the temperature it is supplied. As the droplets evaporate they extract sensible
from the surrounding air at a rate of approximately 1,000 BTU per pound of water evaporated.
This causes the temperature of the air to decrease, meaning that both humidity and cooling are
provided simultaneously. This could be a significant energy saving technique if mechanical
cooling is required. Since humidification is most often required when the exterior atmospheric
temperature is below room temperature, there is a necessity to warm the air either prior to
addition of the water droplets or after absorption of the droplets into the air. It is recommended
to add the moisture after the air is heated as this dramatically reduces the time and distance
taken for the water droplets to evaporate.
Humidification Zones (In Space Applications)
The movement of humidity through a space is very rapid. In applications where accurate
humidity control is essential, it is important that the structure be reasonably air-tight, well
insulated, and have good vapor barriers, to prevent humidity from escaping to the outside. If a
large amount of infiltration or exfiltration is encountered it may be necessary to oversize the
system to compensate for this.
AFE systems are frequently used in large factory applications for dust and static suppression.
Often these structures have large doors open for loading and unloading of goods. Keeping
doors closed, except when needed for movement of goods, can improve the performance of the
humidification system by containing humidity levels within the space.
Absorption Distance
Water mist sprayed by the AFE nozzle requires a certain distance to be absorbed by the air.
Absorption distance is affected by many factors including temperature, existing humidity levels
and air pressure. However, in general increasing the air pressure (and hence the water flow) to
the nozzle will increase the absorption distance since more water is being sprayed. It is
important to follow the clearances in this guide to prevent the accidental wetting of structures
or machinery.