Cooling water in cooling towers and other open systems

Here, one is confronted with all conceivable problems that the combination of water and cooling entails:

• Limestone and stone deposits
• Corrosions
• Algae or bacteria infestation
• Deposits of dirt particles, sand, etc.

In the cooling tower, only pure water evaporates, leading to the well-known accumulation of dissolved salts. This, in turn, soon causes the solubility limit of the salts to be exceeded, resulting in deposits in the cooling system. Therefore, a portion of the cooling water must always be removed (elutriated=desalinated) to prevent the solubility limit of the dissolved salts from actually being reached. However, the more water is removed, the greater the water consumption, which directly impacts the operating costs of the cooling system. Adding appropriate hardness stabilizers can reduce the amount removed, thus saving water; however, this increases the densification (C) in the cooling circuit.

C = Salt concentration in cooling circuit water / Salt concentration in make-up water

Z = Amount of additional water
C = Densification

As can be seen from the diagram, an increase in the densification C from 1.5 to 3 already leads to a reduction in water requirements of 50%.

The diagram also shows that the relationship between Z and C is a hyperbolic function – it follows that further increases in densification lead to further, but increasingly smaller, water savings.

Since air is continuously introduced into the system via the cooling tower, the cooling water is also considered to be extremely aggressive; for this reason, the addition of a corrosion inhibitor is recommended to increase the service life of the cooling system.

Introducing air into the cooling circuit water also promotes the growth of bacteria and algae. These can form deposits that reduce heat transfer in the refrigeration units and lower cooling capacity; they also exacerbate aeration corrosion. Microbiological growth in the cooling tower can be prevented by using special biocides, which, however, must be compatible with the water hardness stabilizers used.

The following diagram shows an example of successful cooling water treatment:

Optimal cooling water treatment can yield the following advantages:

• Increased potential for densification – therefore a significant water saving.
• Prevention of stone and dirt deposits – therefore optimal heat transfer and full cooling performance
• Prevention of microbiological deposits – therefore improved heat transfer (better cooling performance) and less corrosion
• Corrosion protection – therefore extending the service life of the system.

We can offer the following product lines for cooling towers:

• MINIPOL
• MIKROBIZID