WHAT IS A COOLING TOWER AND HOW DOES IT WORK?
A
cooling tower is basically a heat exchanger where water and air are brought into contact with each other to reduce the water's temperature. As this happens, a small amount of water is evaporated, lowering the temperature of the circulated water throughout the tower.
Water, which has bcome heated by industrial processes or in an air-conditioning condenser, gets pumped to the cooling tower through pipes. The water flows through nozzles that spray water into the material called "fill media," which slows down the flow of water through the cooling tower, and exposes as much of the water surface as possible for maximum air-water contact. As the water spils down through the cooling tower, it gets exposed to air, which is being pulled through the tower by the electric cooling tower motor-driven fan.
When the air and water meet, a small amount of the water is evaporated, creating a cooling like action. The cooled water then gets pumped back to the process equipment or condenser where it becomes reheated. It will then be re-pumped back to the cooling tower to be cooled once again.
TYPES OF COOLING TOWERS
Cooling towers are manufactured and designed in several different types, with numerous sizes available. Not all cooling towers are suitable for all applications. Understanding the various
cooling tower types, along with their advantages and disadvantages, is very important when determining the right cooling tower for a project. The product list below provides an overview of towers to help you determine which is right for your application.
Factory-assembled towers (FAP)
Factory-assembled cooling towers undergo complete assembly at their point of manufacture, where they are shipped to the site in as few sections as the mode of transportation will permit. A relatively small cooling tower would ship essentially intact. A bigger, multi-cell cooling tower is assembled as modules at the factory, and are shipped with appropriate hardware for assembly by the user. Factory-assembled towers also go by the name "packaged" or "FAP" towers. Factory-assembled cooling towers can be counterflow, crossflow, induced draft or forced draft, depending on the cooling tower application. While all applications may be different, the Marley NC crossflow, induced draft cooling tower is widely used for HVAC and light industrial applications.
Field-erected cooling towers (FEP)
Field-erected cooling towers are primarily constructed at the site of ultimate use. All large cooling towers, and many of the smaller towers, are prefabricated, piece-marked, and shipped to the site for final assembly. The manufacturer commonly provides supervision and labor for final assembly. Field-erected towers can be crossflow or counterflow, depending on the application. For power and heavy industrial applications, the Marley F400 counterflow tower can be customized to meet your exact specifications for performance, structure, drift and plume abatement.
Crossflow cooling towers
In crossflow type cooling towers the water will fall vertically through the fill media while the air flows horizontally, across the flow of the falling water. Because of this, air does not have to pass through the distribution system, permitting the use of gravity flow hot water distribution basins mounted at the top of the unit above the fill. These basins are generally applied on all crossflow towers.
Counterflow cooling towers
Counterflow cooling towers are designed so that air flows vertically upward, counter to the flow of falling water in the fill media. Because of this vertical airflow, it is not possible to use the open, gravity-flow basins commonin crossflow designs. Instead, counterflow towers use pressurized, pipe-type spray systems to spray water onto the top of the fill media. Since air has to be able to pass through the spray system, the pipes and nozzles must be much farther apart so as not to restrict airflow.
Induced draft vs. forced draft
Induced draft cooling towers have fans that are typically mounted on top of the unit and pull air through the fill media. Conversely, the air is pushed by blowers located at near base of the air inlet face on forced draft towers.
PERFORMANCE DRIVERS
Optimally designed system - Using a total system approach, every unit and component is designed and engineered to work together as an integrated system for efficient performance and long life.
HVAC Cooling - A cooling system allows the tower to directly satisfy a building's cooling needs without the need of operating the chiller in cold weather. The goal of a free cooling system is to save energy. There are specific types of free cooling systems and certain elements that must be in place for a free cooling system to be considered.
Mu Flow - There may be energy savings opportunities if the cooling tower can be operated under variable flow in off-peak conditions. Variable flow is one way to increase the effectiveness of the installed tower capacity for whatever flow the process has.
OEM parts - Precision-engineered to provide a reliable product, OEM parts are built to the highest standards and tightest tolerances for extended service life.
Geareducer� Solutions - Gearboxes are available in a variety of designs and reduction ratios to accommodate the different fan speeds and horsepowers of cooling towers.
Cooling Tower Parts
Fill Media
One of the single most important components of a cooling tower is the fill. Its ability to promote both the maximum contact surface and the maximum contact time between air and water determines the efficiency of the cooling tower. The two basic fill media classifications are splash type fill (breaks up the water) and film type fill (spreads the water into a thin film).
Drift eliminators
Drift eliminators are designed to remove water drops from the discharged air, drift eliminators cause the air/droplets to make sudden changes in direction. This causes the drops of water to become separated from the air and deposited back into the tower.
Nozzles
Crossflow cooling tower configuration permits the use of a gravity-flow distribution system with a nozzles. With this system, the supply of water is elevated to hot water distribution basins above the fill and then flows over the fill (by gravity) through nozzles located in the distribution basin floor. Counterflow configuration necessitates the use of a pressure type system of closed pipe and spray nozzles.
Water Level Controls
Automatic water level controllers help ensure your water stays filled to the adequate level at all times. They use signals that pass through rods to turn on and off pumps automatically and can save you a ton of money vs traditional float switches. Check out the
advantages and disadvantages of water level controls.
Fans
Cooling tower fans must move huge volumes of air efficiently, and with only a little vibration. The materials of manufacturer must not only be compatible with their design, but must also be capable of withstanding the corrosive effects of the harsh environment in which the fans are required to operate.
Driveshafts
The driveshaft transmits the power from the output shaft in the motor to the input shaft of the Geareducer. Because the driveshaft operates within the tower, it must be highly corrosion resistant. Turning at full motor speed, it must be well balanced and capable of being re-balanced. Due to the rigorous cooling tower specification requirement special driveshafts had to be designed.
For specific information on how SPX Cooling Technologies can meet your needs, contact your local Universal Cooling Tower sales representative at
universalcoolingtowerproducts.com/how-do-cooling-towers-work.htm.
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