Enhanced tubes considerably improved heat transfer due to greater surface area, but the water treatment must be improved substantially to keep them from fouling.

Cooling tower water systems are composed of three major sections: cooling tower, chiller or heat exchangers, and piping. Each section must be considered when designing a cooling tower water system. Often, initial capital cost of equipment is a strong driving force. Little, if any, water treatment costs are incorporated in the design and equipment purchase decision.

So, if you choose the lowest cost of these three major sections, this would most likely include:

  • Cooling tower: galvanized steel.
  • Chiller: copper or carbon steel tubes.
  • Piping: carbon steel.
  • No filters.

The result is a good cooling tower water system from operation, but the water treatment requirements are considerable because the following are needed:

  • Carbon steel corrosion inhibitor.
  • Copper corrosion inhibitor.
  • Galvanized steel corrosion inhibitor.
  • Deposit and bio-control chemicals.


Decisions on the selection of either lowest or higher cost equipment, or in between, must involve a thorough review prior to issuing a request for quote (RFQ) from vendors for a new cooling tower system or to rebuild an older model.

In addition, it is important to maintain lower levels of cooling tower water minerals to keep suspended and dissolved solids to a minimum. Thus, operating costs for water treatment can be substantial, plus you must pay greater attention to water chemistry control and monitoring, and likely there will be more water use.

Even utilizing partially softened cooling tower makeup water can essentially eliminate scale-inhibitor use. Utilizing a filter designed to filter 3 percent to 5 percent of the cooling tower recirculation rate will reduce and possibly eliminate use of a dispersant and reduce the need for microbiological control chemicals. Also, utilizing ozone or ultraviolet light can eliminate the use of microbiocides and still provide good microbiological control.

What is the difference in initial and operating costs for these two extremes? The precise answer is site-specific and requires considering other factors such as local codes, water quality, operator-required effort and time, plus how long the facility and management wish the various portions of the system to last before repair and replacement are needed. Yet, a rough comparison can be made for systems installed in the United States, which will likely vary somewhat in other countries (table 1).

Decisions on the selection of either lowest or higher cost equipment, or in between, must involve a thorough review prior to issuing a request for quote (RFQ) from vendors for a new cooling tower system or to rebuild an older model. Input from management, purchasing, operations, utility managers and environmental personnel is essential. Guidance can be provided by consultants knowledgeable not only on the equipment available but also the water treatment needs.

So, what do you decide for your cooling tower system? Seek advice from knowledgeable consultants, particularly those who do not sell chemicals or equipment.



Sidebar: Don't Forget

Other items that can influence your selection of equipment are:

  • The type of fill in the cooling tower.
  • The special water treating needs of enhanced copper tubes, if used.
  • The water quality.
  • Whether environmental restrictions limit various chemical use.
  • Any contaminants that are entering or can enter the system.
  • Whether the cooling tower system operates 24/7 or is shut down periodically.


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