Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include cooling the circulating water used in oil refineries, chemical plants, power stations and building cooling. The towers vary in size from small roof-top units to very large hyperboloid structures that can be up to 200 metres tall and 100 metres in diameter, or rectangular structures that can be over 40 metres tall and 80 metres long. Smaller towers are normally factory-built, while larger ones are constructed on site.
A hyperboloid cooling tower was patented by Frederik van Iterson and Gerard Kuypers in 1918.
Functions
Cooling Towers have one function:
- Remove heat from the water discharged from the condenser so that the water can be discharged to the river or recirculated and reused.
Some power plants, usually located on lakes or rivers, use cooling towers as a method of cooling the circulating water (the third non-radioactive cycle) that has been heated in the condenser. During colder months and fish non-spawning periods, the discharge from the condenser may be directed to the river. Recirculation of the water back to the inlet to the condenser occurs during certain fish sensitive times of the year (e.g. spring, summer, fall) so that only a limited amount of water from the plant condenser may be discharged to the lake or river. It is important to note that the heat transferred in a condenser may heat the circulating water as much as 40 degrees Fahrenheit (F). In some cases, power plants may have restrictions that prevent discharging water to the river at more than 90 degrees F. In other cases, they may have limits of no more than 5 degrees F difference between intake and discharge (averaged over a 24 hour period). When Cooling Towers are used, plant efficiency usually drops. One reason is that the Cooling Tower pumps (and fans, if used) consume a lot of power.
Major Components
Cooling Tower(Supply) Basin
Water is supplied from the discharge of the Circulating Water System to a Distribution Basin, from which the Cooling Tower Pumps take a suction.
Cooling Tower Pumps
These large pumps supply water at over 100,000 gallons per minute to one or more Cooling Towers. Each pump is usually over 15 feet deep. The motor assembly may be 8 to 10 feet high. The total electrical demand of all the Cooling Tower pumps may be as much as 5% of the electrical output of the station.
