Cooling towers costs

JUONG, J. F. Hydrocarbon Process., 48(7) (1969) 200. How to estimate cooling tower costs. 

Maintenance cost. Maintenance for air-cooled equipment as compared with shell-and-tube coolers (complete with cooling-tower costs) indicates that air-cooling maintenance costs are approximately 0.3 to 0.5 those for water-cooled equipment. 

Other energy considerations for cooling towers include the use of two-speed or variable-speed drives on cooling-tower fans, and proper cooling-water chemistry to prevent fouling in users (see Water, industrial water treatment). Air coolers can be a cost-effective alternative to cooling towers at 50—90°C, just below the level where heat recovery is economical. 

The second law of thermodynamics focuses on the quaUty, or value, of energy. The measure of quaUty is the fraction of a given quantity of energy that can be converted to work. What is valued in energy purchased is the abiUty to do work. Electricity, for example, can be totally converted to work, whereas only a small fraction of the heat rejected to a cooling tower can make this transition. As a result, electricity is a much more valuable and more costly commodity. 

Cost particularized by tbe subscript Installed cost of a cooling tower Installed cost of a deminerabzed-water system... 

Water Systems These systems usually form the third highest cost item in chemical-plant anxiharies, with cooling towers representing the largest part of the investment. Although the installed cost increases with the terminal temperature range, an approximate cost correlation is given by... 

Cooling Water System. A list of cooling duties will be available at this point so the cost estimate for this system can be factored or estimated based on a similar operating system. For a more definitive estimate based on initial or detailed layout, it is probably best to use a contractor or consultant skilled in these designs. If a cooling tower is involved, the groundwork will already have been set. This basis can be passed along on specification sheets provided in the Appendix to a vendor for quotes. 

Although these units find initial application in areas of limited water, they have not been limited to this situation. In many instances they are more economical than cooling tower systems and have been successfully applied in combination with cooling towers (see Figure 10-184). Economic comparisons should include such items as tower costs, basin, make-up facilities, water treatment, pumps for circulation, power supply, blow down, piping, etc. For small installations of air-cooled units, they should be compared... 

As an example, the reputable cooling tower designer would establish most of the above parameters from his own experience. In addition, he could determine with his client the economic factors which could influence his selection, i.e. low capital cost with high mnning costs, or a higher capital cost with more acceptable power costs (a 12-month or a 5-year payback period). Turnkey contractors often understandably ignore this particular factor, and end users should always obtain alternative designs to make their own selection. 

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