components of cooling towers and how to improve water efficiency of the system as a part of a comprehensive approach to water management. In this Fact Sheet . Cooling Tower. Fundamentals. Compiled from the knowledge and experience of the entire SPX Cooling Technologies staff. Edited by. John C. Hensley. A cooling tower is a heat rejection device that rejects waste heat to the atmosphere through the "Technical Information for Cooling Towers Using Recycled Water" (PDF). terney.info San Diego County Water Authority. Retrieved 18 June.
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What is a cooling tower? Cooling towers are a special type of heat exchanger that allows water and air to come in contact with each other to lower the. Cooling towers are a very important part of many chemical plants. The primary The water exits the cooling tower and is sent back to the exchangers or to other. the ambient dry-bulb temperature-too high for the cooling water requirements of most refrigeration systems and many industrial pro- cesses. Cooling towers.
EMAIL ravispatel hotmail. Patel Polytechnic,Kherva,Mehsana. Patel, we would also like to thank our respected principal B. And special thank to Prof. Topics Name Page No. But finally we decided to select the Induced draft cooling tower. As a project. For that first we collected all the required material like MS sheet, PVC pipes, Fins, Wire mesh, exhaust fan, Stand, Nut and bolts and some other material for cooling tower. After this all and after some operations like cutting, bending, welding and fitting.
Finally we assembled the parts of our project with final testing. In this project of Induced draft cooling tower, we are clever students is participate are as follow. The gap could also negative. It is caused due to continuous operation of machine and atmospheric conditions of the surroundings. Operation cannot be stopped or in other words the machine cannot be given time to be cooled down and therefore there has to be provision for cooling.
Water is the best cooling medium as it is cheap and available in abundance. However it has to be noted that continuous flow of fresh water to the machine is not advisable as it creates great waste. Cooling tower is used to fulfil the purpose of cooling with minimum usage of fresh water.
It circulates fresh water for cooling to the machine and uses least make up water that is lost due to evaporation. Apart from industry cooled water is needed for, for example, air conditioners, or power generation.
A cooling tower is the equipment used to reduce the temperature of a water stream by extracting heat from water and emitting it to the atmosphere. Cooling towers make use of evaporation whereby some of the water is evaporated into a moving air stream and subsequently discharged into the atmosphere.
As a result, the remainder of the water is cooled down significantly as shown in the figure. Cooling towers are able to lower the water temperatures more than devices that use only air to reject heat, like the radiator in a car, and are therefore more cost-effective and energy efficient.
At the top is a set of distributing troughs, to which the water from the condenser must be pumped; from these it trickles down over "mats" made of wooden slats or woven wire screens, which fill the space within the tower.
A hyperboloid cooling tower was patented by the Dutch engineers Frederik van Iterson and Gerard Kuypers in The first ones in the United Kingdom were built in at Lister Drive power station in Liverpool , England, to cool water used at a coal-fired electrical power station. An HVAC heating, ventilating, and air conditioning cooling tower is used to dispose of "reject" unwanted heat from a chiller.
Water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat rejection to tower water at or near wet-bulb temperatures. Air-cooled chillers must reject heat at the higher dry-bulb temperature , and thus have a lower average reverse- Carnot cycle effectiveness. In areas with a hot climate, large office buildings, hospitals, and schools typically use one or more cooling towers as part of their air conditioning systems.
Generally, industrial cooling towers are much larger than HVAC towers. HVAC use of a cooling tower pairs the cooling tower with a water-cooled chiller or water-cooled condenser.
Cooling towers are also used in HVAC systems that have multiple water source heat pumps that share a common piping water loop. In this type of system, the water circulating inside the water loop removes heat from the condenser of the heat pumps whenever the heat pumps are working in the cooling mode, then the externally mounted cooling tower is used to remove heat from the water loop and reject it to the atmosphere.
By contrast, when the heat pumps are working in heating mode, the condensers draw heat out of the loop water and reject it into the space to be heated. When the water loop is being used primarily to supply heat to the building, the cooling tower is normally shut down and may be drained or winterized to prevent freeze damage , and heat is supplied by other means, usually from separate boilers. Industrial cooling towers can be used to remove heat from various sources such as machinery or heated process material.
The primary use of large, industrial cooling towers is to remove the heat absorbed in the circulating cooling water systems used in power plants , petroleum refineries , petrochemical plants, natural gas processing plants, food processing plants, semi-conductor plants, and for other industrial facilities such as in condensers of distillation columns, for cooling liquid in crystallization, etc.
If that same plant had no cooling tower and used once-through cooling water, it would require about , cubic metres an hour  A large cooling water intake typically kills millions of fish and larvae annually, as the organisms are impinged on the intake screens.
Furthermore, discharging large amounts of hot water may raise the temperature of the receiving river or lake to an unacceptable level for the local ecosystem. Elevated water temperatures can kill fish and other aquatic organisms see thermal pollution , or can also cause an increase in undesirable organisms such as invasive species of zebra mussels or algae. A cooling tower serves to dissipate the heat into the atmosphere instead and wind and air diffusion spreads the heat over a much larger area than hot water can distribute heat in a body of water.
Evaporative cooling water cannot be used for subsequent purposes other than rain somewhere , whereas surface-only cooling water can be re-used. Some coal-fired and nuclear power plants located in coastal areas do make use of once-through ocean water.
But even there, the offshore discharge water outlet requires very careful design to avoid environmental problems. Petroleum refineries also have very large cooling tower systems. These types of cooling towers are factory preassembled, and can be simply transported on trucks, as they are compact machines. The capacity of package type towers is limited and, for that reason, they are usually preferred by facilities with low heat rejection requirements such as food processing plants, textile plants, some chemical processing plants, or buildings like hospitals, hotels, malls, automotive factories etc.
Due to their frequent use in or near residential areas, sound level control is a relatively more important issue for package type cooling towers. Facilities such as power plants, steel processing plants, petroleum refineries, or petrochemical plants usually install field erected type cooling towers due to their greater capacity for heat rejection.
Field erected towers are usually much larger in size compared to the package type cooling towers. A typical field erected cooling tower has a pultruded fiber-reinforced plastic FRP structure, FRP cladding , a mechanical unit for air draft , drift eliminator. With respect to the heat transfer mechanism employed, the main types are:.
In a wet cooling tower or open circuit cooling tower , the warm water can be cooled to a temperature lower than the ambient air dry-bulb temperature, if the air is relatively dry see dew point and psychrometrics. As ambient air is drawn past a flow of water, a small portion of the water evaporates, and the energy required to evaporate that portion of the water is taken from the remaining mass of water, thus reducing its temperature.
Evaporation results in saturated air conditions, lowering the temperature of the water processed by the tower to a value close to wet-bulb temperature , which is lower than the ambient dry-bulb temperature , the difference determined by the initial humidity of the ambient air.
To achieve better performance more cooling , a medium called fill is used to increase the surface area and the time of contact between the air and water flows. Splash fill consists of material placed to interrupt the water flow causing splashing.
Film fill is composed of thin sheets of material usually PVC upon which the water flows. Both methods create increased surface area and time of contact between the fluid water and the gas air , to improve heat transfer. Hyperboloid sometimes incorrectly known as hyperbolic cooling towers have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material.
The hyperboloid shape also aids in accelerating the upward convective air flow, improving cooling efficiency. These designs are popularly associated with nuclear power plants. However, this association is misleading, as the same kind of cooling towers are often used at large coal-fired power plants as well. Conversely, not all nuclear power plants have cooling towers, and some instead cool their heat exchangers with lake, river or ocean water. Crossflow is a design in which the air flow is directed perpendicular to the water flow see diagram at left.
Air flow enters one or more vertical faces of the cooling tower to meet the fill material.
Water flows perpendicular to the air through the fill by gravity. The air continues through the fill and thus past the water flow into an open plenum volume. Lastly, a fan forces the air out into the atmosphere. A distribution or hot water basin consisting of a deep pan with holes or nozzles in its bottom is located near the top of a crossflow tower.
Gravity distributes the water through the nozzles uniformly across the fill material. In a counterflow design, the air flow is directly opposite to the water flow see diagram at left. Air flow first enters an open area beneath the fill media, and is then drawn up vertically. The water is sprayed through pressurized nozzles near the top of the tower, and then flows downward through the fill, opposite to the air flow.
Both crossflow and counterflow designs can be used in natural draft and in mechanical draft cooling towers.
Quantitatively, the material balance around a wet, evaporative cooling tower system is governed by the operational variables of make-up volumetric flow rate , evaporation and windage losses, draw-off rate, and the concentration cycles.
In the adjacent diagram, water pumped from the tower basin is the cooling water routed through the process coolers and condensers in an industrial facility. The cool water absorbs heat from the hot process streams which need to be cooled or condensed, and the absorbed heat warms the circulating water C.
The warm water returns to the top of the cooling tower and trickles downward over the fill material inside the tower. As it trickles down, it contacts ambient air rising up through the tower either by natural draft or by forced draft using large fans in the tower. That contact causes a small amount of the water to be lost as windage or drift W and some of the water E to evaporate.
The heat required to evaporate the water is derived from the water itself, which cools the water back to the original basin water temperature and the water is then ready to recirculate.
The evaporated water leaves its dissolved salts behind in the bulk of the water which has not been evaporated, thus raising the salt concentration in the circulating cooling water. To prevent the salt concentration of the water from becoming too high, a portion of the water is drawn off or blown down D for disposal.
Fresh water make-up M is supplied to the tower basin to compensate for the loss of evaporated water, the windage loss water and the draw-off water. A water balance around the entire system is then: Since the evaporated water E has no salts, a chloride balance around the system is: Windage or drift losses W is the amount of total tower water flow that is entrained in the flow of air to the atmosphere.
From large-scale industrial cooling towers, in the absence of manufacturer's data, it may be assumed to be:. Cycle of concentration represents the accumulation of dissolved minerals in the recirculating cooling water. Discharge of draw-off or blowdown is used principally to control the buildup of these minerals. The chemistry of the make-up water, including the amount of dissolved minerals, can vary widely. Make-up waters low in dissolved minerals such as those from surface water supplies lakes, rivers etc.
Make-up waters from ground water supplies such as wells are usually higher in minerals, and tend to be scaling deposit minerals. This method works on the principle that continuous particle removal will keep the system clean. Manufacturers typically package side-stream filters on a skid, complete with a pump and controls.
For high flow systems, this method is cost-effective.
Properly sizing a side-stream filtration system is critical to obtain satisfactory filter performance, but there is some debate over how to properly size the side-stream system. Cycle of concentration — Maximum allowed multiplier for the amount of miscellaneous substances in circulating water compared to the amount of those substances in make-up water.
Treated timber — A structural material for cooling towers which was largely abandoned in the early s. It is still used occasionally due to its low initial costs, in spite of its short life expectancy. The life of treated timber varies a lot, depending on the operating conditions of the tower, such as frequency of shutdowns, treatment of the circulating water, etc. Under proper working conditions, the estimated life of treated timber structural members is about 10 years.
Leaching — The loss of wood preservative chemicals by the washing action of the water flowing through a wood structure cooling tower. Pultruded FRP — A common structural material for smaller cooling towers, fibre-reinforced plastic FRP is known for its high corrosion-resistance capabilities. Pultruded FRP is produced using pultrusion technology, and has become the most common structural material for small cooling towers. It offers lower costs and requires less maintenance compared to reinforced concrete, which is still in use for large structures.
Fog produced by Eggborough power station Under certain ambient conditions, plumes of water vapor can be seen rising out of the discharge from a cooling tower, and can be mistaken as smoke from a fire. If the outdoor air is at or near saturation, and the tower adds more water to the air, saturated air with liquid water droplets can be discharged, which is seen as fog.
This phenomenon typically occurs on cool, humid days, but is rare in many climates. Fog and clouds associated with cooling towers can be described as homogenitus, as with other clouds of man-made origin, such as contrails and ship tracks. For that purpose, in hybrid towers, saturated discharge air is mixed with heated low relative humidity air. Some air enters the tower above drift eliminator level, passing through heat exchangers. The relative humidity of the dry air is even more decreased instantly as being heated while entering the tower.
The discharged mixture has a relatively lower relative humidity and the fog is invisible. The salt deposition problem from such cooling towers aggravates where national pollution control standards are not imposed or not implemented to minimize the drift emissions from wet cooling towers using seawater make-up. Similarly, particles smaller than 2. Though the total particulate emissions from wet cooling towers with fresh water make-up is much less, they contain more PM10 and PM2. At plants without flue gas purification, problems with corrosion may occur, due to reactions of raw flue gas with water to form acids.
Sometimes, natural draft cooling towers are constructed with structural steel in place of concrete RCC when the construction time of natural draft cooling tower is exceeding the construction time of the rest of the plant or the local soil is of poor strength to bear the heavy weight of RCC cooling towers or cement prices are higher at a site to opt for cheaper natural draft cooling towers made of structural steel.
Operation in freezing weather[ edit ] Some cooling towers such as smaller building air conditioning systems are shut down seasonally, drained, and winterized to prevent freeze damage. Basin heaters, tower draindown, and other freeze protection methods are often employed in cold climates.