Cooling tower general construction

Natural and forced-draft cooling towers are generally used to provide the cooling water required on a site, unless water can be drawn from a convenient river or lake in sufficient quantity. Seawater or brackish water can be used at coastal sites, but if used directly will necessitate more expensive materials of construction for heat exchangers. 

Natural-draft cooling towers with a hyperbolic configuration are usually constructed of concrete, have a large dimension and, consequently, large capacities. They are generally used in power plants. Figure 4.3 also illustrates this design. 

Mechanical-draft cooling towers can be either field-constructed or factory-assembled systems. Installations that are constructed onsite are generally those employed at utility stations. Factory-assembled towers have applications in smaller industrial operations. 

Plant operations personnel generally purchase cooling towers rather than construct them themselves. The philosophy behind this policy is that it makes available to operators a wealth of practical knowledge directly applicable in the field. The operator must specify the amount of water and the temperature range required to handle a specific set of process conditions. It is the fabricator s responsibility to propose a system that will meet the operator-furnished conditions for the 5% wet-bulb in the plant locality. This also means that the fan power with which the operation will be accomplished will be guaranteed. 

Atmospheric conditions should be defined in terms of temperature, humidity, and contaminants, as well as their corrosivity to the specific materials of construction being considered. In addition to the general atmospheric conditions, special conditions such as cooling tower drift or spray, spills, or releases of water or chemicals should not be overlooked and must be taken into account. 

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