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On the surface it would appear that evaporation in a
cooling tower would not have a negative affect on the cooling water chemistry.
However, we must remember that most of the water we encounter is not
"pure". Specifically, when a raindrop falls through the atmosphere it
collects a variety of dissolved gases.
Once that drop contacts the earth’s surface, it picks
up their contaminants such as dissolved and suspended solids. In essence, by the
time the water is used for cooling tower makeup, it contains a variety of
contaminants. These contaminants, coupled with process leaks or other surface
contaminants, intensify the potential water problems in a cooling system.
 The cooling tower magnifies the potential water problems
in two ways.
- First, the tower acts as a giant air washer.
As large quantities of air are brought into contact with
the cooling water, the water scrubs out any
Impurities the air may contain.
- Second, changes in the water chemistry occur during
the evaporation process.
- Third, temperature variations across the system.
- Fourth, a noticeable residence time in the system,
permiting side reactions, biological growths etc.
The main problems occuring in Open
recirculation Cooling Water Systems are falling into the following categories :
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