The water that is evaporated at the cooling tower is pure, that is, it doesnt contain any of the dissolved minerals present in the makeup. Water treatment for cooling towers 1 of 2 water treatment helps ensure that heattransfer surfaces perform to design specifications by amanda meitz, senior microbiologist, nalco diversified technologies, inc. A cooling tower removes heat by evaporative cooling of a recirculating stream of cooling water. Cooling tower water chemistry parameters water treatment. Water quality required for trouble free cooling tower operation the water must not contain solid particles which may deposit in the cooling water system. Jul 30, 2018 some of the commonly used useful terms, in the cooling tower industry are. Background correct cooling water treatment and followup of the cooling water condition are of utmost importance for keeping the cooling water systems of the engines in good condition. This type of heat rejection is termed evaporative because it allows a. A key parameter used to evaluate cooling tower operation is cycles of concentration sometimes referred to as cycles or concentration ratio. Cooling tower efficiency calculations cooling tower efficiency calculation is described in this article. Cooling tower useful terms and cooling tower performance. Typical closed loop cooling tower system is shown in figure 7.
Due to the nature of evaporative cooling units, water lost from evaporation and blowdown has to be replenished. Dec 04, 2017 the purpose of a cooling tower is to conserve water. They evolve from the crossflow concept of towers pioneered by marley in 1938. The resulting lower temperature cooling water is returned to the condenser, and the amount of water that. Arnold schwarzenegger governor cooling tower water quality. Cooling water systems are constantly inoculated with microbes from the makeup water, process contamination and the air. Cooling towers with open and closed water circuits are available.
When the solids concentration in the cooling tower water is triple that of. A basic understanding of the system water distribution shall be established in order to properly operate and maintain a cooling tower on a water efficient manner. The heat picked up in the heat exchanger is returned to the cooling tower where it is rejected to the atmosphere by evaporative and convective cooling. Dry cooling tower an overview sciencedirect topics. This allows steam to evaporate each time the cooling water.
As the water evaporates, the air absorbs heat, which lowers the temperature of the remaining water. Water leaks in the process or in the cooling tower itself are uncontrolled water loses that could be considered another form of blowdown. Target parameters should be established and maintained that will control fouling and. All the water passing through the fill should go into the basin. The cooling tower must be adequately sized to reject this same amount of. They reject process heat from the cooling water to atmosphere and keep the water cool. Water may be treated with chemical inhibitors to extend the saturation point of insoluble materials and prevent scaling and corrosion. However if the system is constructed of fiberglass, this water quality parameter is less of a problem. Cooling tower evaporative cooling system measurement and. These measured parameters and then used to determine the cooling tower performance in several ways. Chemical treatment of water for cooling and heating systems. Best management practice and guidance manual for cooling. Open recirculating cooling water systems utilize cooling towers to reject heat through.
Improper blowdown and makeup may lead to reduced ph, corrosion, and higher water consumption. The amount of water evaporated from the cooling tower is a function of the recirculation rate and cooling range. Maintain cooling tower fill to prevent water from dripping or sloshing from the fill and onto the ground. Those theories are briefly described in this guideline to provide the. In order to promote public education and public safety, equal justice for all, a better informed citizenry, the rule of law, world trade and world peace, this legal document is hereby made available on a noncommercial basis, as it is the right of all humans to. Cooling tower evaporative cooling system measurement and verification protocol guidelines for energy service companies and water efficiency service companies to determine water savings of cooling tower efficiency measures for use in performance contracts.
Water outputs from a cooling tower include controlled losses such as evaporation, bleed, drift and pump gland leakage and uncontrolled losses including leaks, splash out, overflows and windage. Water efficiency management guide mechanical systems. Pdf design and performance analysis of the cooling tower. Making up for limited cooling capacity can erode your profits and increase your energy costs significantly. Cooling range the difference in temperature between the hot water entering the tower and the cold water leaving the tower is the cooling range. As the universal solvent, water is capable of dissolving a variety of materials as well as holding. Best management practice and guidance manual for cooling towers. Again, this will be a first issue releasing the actual engineering approach. Warmer water raises the risk of limited cooling for. Cooling tower bureau of energy efficiency 5 syllabus cooling tower. An introduction to cooling tower water treatment course no. The basics of cooling tower water treatment the purpose of a cooling tower is to remove the heat generated by an hvac system cooling of compressor refrigerant and heat generated by the compressor itself.
This is a closedloop system, in which the cooling water is sent from the condenser to the cooling tower, where the heat of the water transfers to the ambient air primarily by evaporation. Earn leed points with a cooling tower, closed circuit cooler or evaporative condenser. To control concentration of dissolved solids and maintain optimum water. Water quality guidelines water treatment a proper water treatment program, administered under the supervision of a competent water treatment specialist, is an essential part of routine maintenance to ensure the safe operation and longevity of evaporative cooling equipment, as well as. A high ct range means that the cooling tower has been able to reduce the. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wetbulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near. Free cooling is when chilled water is cooled by cooling tower water through the. It is the requirement of heatenergy to increase the temperature by 1 o f of onepond of water between 32 and 212 o f. In technical terms, cooling towers are engineered and designed based on a specified cooling load, expressed in refrigeration tons. The fan deck supports the motor and fan of the water. Water qualityorganic contaminants, such as oil and grease, fertilizers, food products and. In a counterflow cooling tower, water sprays are used to distribute the warm water see figure 8. In a direct dry cooling tower, turbine exhaust steam is condensed directly through an aircooled condenser acc. Lab result shows existence of legionella more than 1 one c.
By contrast, dry cooling towers and wet cooling towers recycle water continuously. Cooling towers manufacturers typically provide limiting and recommended parameters, like conductivity, total dissolved solids, ph. Cooling tower water treatment application note sensorex. Cooling water quality depends on the type of heat exchanger or engine to be cooled. Warm recirculating water is sent to the cooling tower where a portion of the water is evaporated into the air passing through the tower.
Cooling tower cycles of concentration cycle of concentration coc ratio of concentration in dissolved solids blowdown vs makeup water typical coc 2. A psychromehic analysis of the air passing through a cooling tower illustrates this effect figure 2. The water must not precipitate lime, gypsum or other materials into the cooling system at. Cooling tower process is generally related with vapor pressure of water and humidity. Cooling tower efficiency calculations cooling tower approach. Some theories are needed to be understood before an engineer start to sizing a cooling tower. For example, lets assume that a process developing a heat load of 125,000 btumin. Other types of water losses were therefore neglected. A cooling tower is heat removal device that uses water to transfer process waste heat into the atmosphere. Structural components are inert fiberglass composite pultrusions. Cooling towers better buildings initiative department of energy. Earn leed points with a cooling tower, closed circuit. Cooling tower plays a major role in chemical process industry. The water must not nourish the growth of microorganisms.
Annex c typical parameters of potable water, newater and industrial water. All cooling towers operate on the principle of removing heat from water be evaporating a small portion of water that is recirculated through the unit. Technical reference for water conservation in cooling towers. This is the difference between the cooling tower water inlet and outlet temperature. All water lost from the system is replaced by makeup water. See the more detailed explanation of cooling towers systems, diagrams, pictures and principles below table of contents what is a cooling tower how do cooling towers work. I recommend a conditioning program unless your water and enviroment as close to heaven. Very generally, it should have the following quality. The big picture when dealing with a foaming cooling tower is as follows, but will be unique for each system. The major concern during i study the cooling tower theory was how to computerize the cooling tower theory from the calculation of ntu to the cooling tower performance analysis. However, there are some applications designed to use the cooling tower for free cooling. In regions where potable supply is plentiful, cooling towers use potable water for making up the water losses in the cooling tower.
The heat load developed by the process establishes a third parameter hot water temperature coming to the cooling tower. Sometimes related parameters, such as range, approach, effectiveness, liquidtogas ratio lg, wetbulb temperature, cooling water temperature, relative humidity, number of transfer units ntu and other terms create a. The owners of cooling tower installations should maintain proper conditions of the fresh water cooling towers to minimize contamination and nuisances to the public. The fan deck supports the motor and fan of the water spray. Cooling tower water quality parameters for degraded water is the. Controlling microbiological fouling depends upon effective control of all these parameters. The corrosion processes that could occur due to a bad cooling water quality may under certain circumstances be local and by their nature proceed very rapidly. Water quality guidelines baltimore aircoil company. The heat load developed by the process establishes a third parameter hotwater temperature coming to the cooling tower. Almost 14 th of makeup water water added in a cycle to substitute water losses in a cooling tower is dissipated 25. The water exits the cooling tower and is sent back to the exchangers or to other units for further cooling.
The cooling effect occurs because some of the water evaporates into a stream of air in contact with the water within the cooling tower. Water treatment cooling towers, evaporative condensers, ice. Biological control is also required to reduce the growth of bacteria and algae. Water quality required for trouble free cooling tower operation. Here we explain in full detail how does a cooling tower work, cooling tower working principles with example text, pictures and diagrams. Open recirculating cooling water systems utilize cooling towers to reject heat through the process of evaporation. The information from this project contributes to piers energyrelated environmental research program. However if the system is constructed of fiberglass, this water quality parameter. A guideline on good operation and maintenance practice of fresh water cooling towers pdf format 2.
Various misconceptions arise when it comes to the thermal design of cooling towers. Technical reference for water conservation in cooling towers 1st edition. In fact, experts estimate that improperly maintained cooling towers consume 2. A cooling tower is a heat rejection device that extracts waste heat to the atmosphere by cooling a stream of hot water in the tower. A simple model to help understand water use at power plants. This process provides significant cooling to the remaining water stream that. Water quality standard for cooling water, cold water, hot water. Technical information for cooling towers using recycled water. Industrialagriculturalwater enduse energy efficiency. Reduce heat transfer, plug orifices, sites for corrosion.
Cooling tower types cooling towers fall into two main categories. As mentioned above, the exact components of a cooling tower water treatment system depend on the quality of feed water and chemistry of circulatory water in relation to the quality of water needed for the specific cooling tower and related equipment according to the manufacturers recommendations, but in general, a basic cooling tower water. The heat load developed by the process establishes a third parameter hot water temperature coming to the tower. The water balance of a tower or cooling water system involves all of the water inputs and outputs associated with the operation of the system. Cooling tower make up has to substitute the water losses resulting from evaporation, windage and blow down. For example, if a system contains 304 ss, chloride levels are an important concern. Cooling tower evaporative cooling system measurement.
Therefore, water treatment is always required in the makeup water of a cooling tower. Makeup water means water added to the cooling tower system on a regular basis to replace water lost. If the cooling tower s conductivity is above parameters, the risk of scale and corrosion increases. As this occurs, a small volume of water is evaporated, reducing the temperature of the water being circulated through the tower. In evaporative cooling products, cooling is accomplished by evaporating a.
Water quality standard for cooling water, cold water, hot. Cooling tower mass balance gives an idea about make up water requirement. Cooling tower water quality parameters for degraded water is the final report for contract number 10098001, conducted by michael n. For more information on the pier program, please visit the energy commissions website at. Water quality guidelines water treatment a proper water treatment program, administered under the supervision of a competent water treatment specialist, is an essential part of routine maintenance to ensure the safe operation and longevity of evaporative cooling equipment, as well as other system components. If you know your water at the inlet, some characteristics like temperatures ect. Cooling tower evaporation transfers heat from hvac systems and other processes into the atmosphere as evaporation occurs, the concentration of mineral salts increases in open recirculating cooling water systems cooling towers. See figure 1 on page 3 for an illustration of the water being recirculated, added to, or lost from a cooling tower.
Water treatment cooling towers, evaporative condensers. Drift eliminators are installed to prevent water entrained in the air from leaving the system. Intent to conserve water used for cooling tower makeup while controlling microbes, corrosion, and scale in the condenser water system. Air enters at the ambient condition point a, absorbs heat and mass moisture from the water. For legionella emergency disinfection purposes, an initial 50 ppm. Cooling tower calculations water technology report. A cooling tower is a heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Water treatment with cooling tower chemicals is preferred to supplying fresh water due to environmental and cost concerns. Cooling tower foaming can damage nearby equipment, ruin paint on cars, and may even be an inhalation source for legionella bacteria.
Technical reference for water conservation in cooling towers pub. Both types function as heat exchangers based on the counter flow principle. The term induced draft denotes that air is drawn by fans through the flow of falling water and up and out of the cooling tower. Chapter 8 cooling towers system shutdown and startup. Realize lions share of savings from coc of 3 to coc of 10, savings level off after coc of 15. If you read this book carefully, you can make any cooling tower design programs by yourself. What is a cooling tower water treatment system and how. An introduction to cooling tower water treatment cedengineering. These guidelines focus specifically on evaporative cooling units. Establishment of the approach fixes the operating temperature of the tower and is a most important parameter in determining both tower size and cost. In the wl 320 open wet cooling tower, water is sprayed into the tower from above and distributed as widely as possible using baffles. The important parameters, from the point of determining the performance of cooling towers, are. Maintain water quality and throughput emerson electric.
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