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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. Recirculati
   Functions   Cooling Towers have one function:    Remove heat from the water discharged from the condenser so that the water can be discharged to theriver 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-spawningperiods, the discharge from the condenser may be directed to the river. Recirculation of the water back to the inlet to thecondenser occurs during certain fish sensitive times of the year (e.g. spring, summer, fall) so that only a limited amountof water from the plant condenser may be discharged to the lake or river. It is important to note that the heat transferredin a condenser may heat the circulating water as much as 40 degrees Fahrenheit (F). In some cases, power plants mayhave restrictions that prevent discharging water to the river at more than 90 degrees F. In other cases, they may havelimits of no more than 5 degrees F difference between intake and discharge (averaged over a 24 hour period). WhenCooling 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 CoolingTower 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 isusually over 15 feet deep. The motor assembly may be 8 to 10 feet high. The total electrical demand of all the CoolingTower pumps may be as much as 5% of the electrical output of the station. Cooling Towers  There are 2 types of towers - mechanical draft and natural draft Mechanical Draft Towers  Mechanical draft Cooling Towers have long piping runsthat spray the water downward. Large fans pull air acrossthe dropping water to remove the heat. As the waterdrops downward onto the fill or slats in the coolingtower, the drops break up into a finer spray. On colderdays, tall plumes of condensation can be seen. Onwarmer days, only small condensation plumes will beseen. Courtesy NSP    Natural Draft Towers  This photo shows a single natural draft cooling tower asused at a European plant. Natural draft towers aretypically about 400 ft (120 m) high, depending on thedifferential pressure between the cold outside air and thehot humid air on the inside of the tower as the drivingforce. No fans are used.Whether the natural or mechanical draft towers are useddepends on climatic and operating requirementconditions. Courtesy KKN - Liebstadt NPP   Simplified Diagrams  The diagrams below illustrate the arrangement of components within the system and the major flow paths. Forced - or Natural Draft Cooling Tower The green flow paths show how the water is takenfrom a river (yellow) to an intake supply basin(green) that the Circ Water Pumps take a suctionfrom. The water is then pumped to the Condenserwhere the water is heated.The water is then sent to an exit distribution basinwhere the water then can be returned to the riverand/or pumped by the Cooling Tower Pumps tothe Cooling Towers then the water returned to theintake supply basin where the water can be reused. Natural Draft Cooling Tower      The green flow paths show how the warmwater leaves the plant proper, is pumpedto the natural draft cooling tower and isdistributed. The cooled water, includingmakeup from the lake to account forevaporation losses to the atmosphere, isreturned to the condenser.  Introduction Federal laws and regulations require Federal agencies to reduce water use and improve water efficiency. Namely, Executive Order 13514 Federal Leadership in Environmental, Energy, and Economic Performance , requires an annual two percent reduction of water use intensity (water use persquare foot of building space) for agency potable water consumption as well as a two percent reduction of water use for industrial, landscaping,and agricultural applications. Cooling towers can be a significant source of water use for both of these categories of water use at Federalfacilities. To realize potential savings it is essential for Federal agencies understand the key components of cooling towers and how to improvewater efficiency of the system as a part of a comprehensive approach to water management. Overview Cooling towers are an integral component of many refrigeration systems, providing comfort or process cooling across a broad range of applications. They are the point in the system where heat is dissipated to the atmosphere through the evaporative process, and are common inindustries such as oil refining, chemical processing, power plants, steel mills, and many different manufacturing processes where process coolingis required. They are also commonly used to provide comfort cooling for large commercial buildings including airports, office buildings,conference centers, hospitals, and hotels.Cooling tower structures vary greatly in size and design, but they all function to provide the same thing: liberation of waste heat extracted from aprocess or building system through evaporation of water. In technical terms, cooling towers are engineered and designed based on a specifiedcooling load, expressed in refrigeration tons. (1) The cooling load is determined by the amount of heat that needs to be extracted from a givenprocess or peak comfort cooling demand. The cooling tower must be adequately sized to reject this same amount of heat to the atmosphere.Cooling towers are used to reject heat through the natural process of evaporation. Warm recirculating water is sent to the cooling tower where aportion of the water is evaporated into the air passing through the tower. As the water evaporates, the air absorbs heat, which lowers thetemperature of the remaining water. This process provides significant cooling to the remaining water stream that collects in the tower basin whereit can be pumped back into the system to extract more process or building heat, thereby allowing much of the water to be used repeatedly to meetthe cooling demand.The amount of heat that can be rejected from the water to the air is directly tied to the relative humidity of the air. Air with a lower relativehumidity has a greater ability to absorb water through evaporation than air with a higher relative humidity, simply because there is less water inthe air. As an example, consider cooling towers in two different locations  –  one in Atlanta, Georgia, and another in Albuquerque, New Mexico.The ambient air temperature at these two locations may be similar, but the relative humidity in Albuquerque on average will be much lower than that of Atlanta’s. Therefore, the cooling tower in Albuquerque will be able to extract more process or building heat and will run at a coolertemperature because the dry desert air has a greater capacity to absorb the warm water.Cooling towers can be split into two distinct categories: open circuit (direct contact) and closed circuit (indirect) systems. In open circuit systemsthe recirculating wat In this Fact Sheet: ã Introduction ã Overview ã Structure ã Basic Cooling Tower Terms ã Types of Towers ã Important Properties of Water ã System Calculations ã Factors That Limit Cycles of Concentration ã System Concerns ã Treatment Options continued > gathering heat and is distributed across the tower where the water is in direct contact with the atmosphere as it recirculates across the towerstructure. Closed circuit systems differ in that the return fluid (often water, or sometimes water mixed with glycol) circulates through the towerstructure in a coil, while cooling tower water recirculates only in the tower structure itself (see Figure 1). In this case, the return fluid is notexposed directly to the air. Structure Cooling towers are the primary component used to exhaust heat in open recirculating cooling systems. They are designed to maximize air andwater contact to provide as much evaporation as possible. This is accomplished by maximizing the surface area of the water as it flows over anddown through the tower structure. Figure 2 illustrates the different components of a cooling tower structure.First, the water is distributed evenly across the top of the cooling tower structure. Tower distribution decks can be a series of spray nozzlesoriented up or down (like a landscaping sprinkler system) to uniformly distribute the water over the tower structure. In some cases, thedistribution deck may just be a series of holes through which the water falls onto the tower structure. Regardless the distribution deck must
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