Cooling tower water consumption

Cooling towers are an important component of refrigeration systems. They are common in industries such as oil & gas , chemical processing, power plants, datacenters . Water is the most common cooling medium used in cooling processes, due to its availability and high heat capacity. These uses require large amounts of water and often present potential for water saving. This savings result in lower water and sewer bills and decreased treatment costs.

In the industrial market there can be found three types of cooling towers: open circuit, closed circuit and once through system. Cooling towers can be air-cooled or water-cooled. Water-cooled cooling towers are more common, as the cooling power of water is stronger than air. Hybrid cooling towers became more and more attractive for Datacenter cooling in central Europe. During low temperature months, air is used for cooling, while in high temperature months, water is used.

Figure 1 - scheme of open circuit cooling tower

The water consumption consists on the control of the make-up water, the blowdown water and the evaporated water quantities. These three waters determine the cycles of concentration that can be reached in the cooling tower. The mass balance of a cooling tower system can be written as the following:

This equation doesn’t take account of the process leaks, the windage and drift which are just forms of uncontrolled blowdown. Moreover, the cycles of concentration is a ratio of the concentration in suspended solids between the blowdown water and the make-up water.

This ratio can be optimized by controlling the cooling tower make-up water (click in new page) quality and the reused cooling tower blowdown (click in new page) quality.

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