Nortec Industries Airfog Series - Manual (Page 10)

10-00
Page 3
2008-04-11
(2) Since AFE nozzle systems use a zero psig water pressure feed network, the
water feed system and nozzles must be horizontal and at the same height as
the water pressure reduction regulator (vacuum valve). Valleys or dips in
altitude will adversely affect performance and in extreme 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.
2. GENERAL AIRFOG TECHNICAL CONSIDERATIONS
A. ADIABATIC COOLING PHENOMENA
(1) 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 the required latent heat of vaporization from the surrounding
air, causing the temperature of the air to decrease. 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.
B. HUMIDIFICATION ZONES (IN SPACE APPLICATIONS)
(1) 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 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.
(2) 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.
C. ABSORPTION DISTANCE
(1) 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.
D. COMPRESSED AIR
(1) NORTEC AIRFOG systems use compressed air as the control fluid. Compressed air
is provided by a compressor (supplied by others) or series of compressors. The
modular approach to the NORTEC AIRFOG systems permits the designer to
consider the cost implications of using multiple smaller horsepower compressors
rather than one very large compressor. By using a multiple compressor design