Cooling Towers Tampa Florida
Introduction Cooling towers are heat exchangers that use water and air to transfer heat from air-conditioning systems to the outdoor environment. Most commonly, they are used to remove heat from the condenser water leaving a chiller. Cooling towers are usually located on rooftops or other outdoor sites. Because they are frequently out of sight, they are often neglected by operation-and-maintenance technicians, resulting in lower cooling-system efficiency. This document will help you adopt best practices for the efficient operation and maintenance of cooling towers. Types of Cooling Towers hereinafter referred to as "CT" or "CTs" There are two basic types of CT's, open and closed (sometimes called direct and indirect). Open (Direct) CTs Open CTs expose the condenser water coming from the chiller plant directly to the atmosphere. This warm water is sprayed over a fill in the CT to increase the contact area, and air passes through the fill. Most of the heat is removed by evaporation. The cooled water remaining after evaporation drops into the collection basin and is returned to the chiller’s condenser.
Open (direct) Cooling Tower Closed (Indirect) Cooling Towers (CT) A closed CT circulates warm water from the chiller plant through tubes located in the tower. In a closed CT, the cooling water does not come in contact with the outside air. Water that circulates only within the CT is sprayed over the tubes and a fan blows air across the tubes. This cools the condenser water within the tubes, which is then recalculated to the chiller plant.
Closed (indirect) CT Key Components of a CT This section explains how the components of a CT work together. Water Distribution Hot water from the chilled-water system is delivered to the top of the CT by the condenser pump through distribution piping. In an open CT, the hot water is sprayed through nozzles onto the heat transfer medium (fill) inside the CT. Some CTs feed the nozzles through pressurized piping; others use a water-distribution basin and feed the nozzles by gravity. In a closed-loop design, the water from the condenser loop runs through tubes and is not exposed to the outside air. In the open CT, a cold-water collection basin at the base of the CT gathers cool water after it has passed through the heat transfer medium. The cool water is pumped back to the condenser to complete the chilled-water loop. In the closed CT, the condenser water cools as it moves through the piping and returns to the chiller plant. Heat Transfer Medium (Fill) CTs use evaporation to release waste heat from an HVAC system. In an open CT, hot water from the condenser is slowed down and spread out over the fill. Some of the hot water is evaporated in the fill area, or over the closed-circuit tubes, which cools the water. CT fill is typically arranged in packs of thin corrugated plastic sheets or as splash bars supported in a grid pattern. Air Flow Large volumes of air flowing through the heat-transfer medium help increase the rate of evaporation and the cooling capacity of the CT. The CT fans generate this airflow. The size of the CT fan and airflow rate are selected to achieve the desired cooling at design conditions of condenser-water temperatures, water flow rate, and wet-bulb temperature.CTs may have propeller fans or squirrel-cage blowers. Small fans may be connected directly to the driving motor, but most designs require an intermediate speed reduction provided by a power belt or reduction gears. The fan and drive system operate in conjunction with the control system to control start/stop and speed. Variable-speed drives (VSDs), when added to the fan motors, control fan speed and more precisely regulate the temperature of the water as it leaves the CT.Drift Eliminator As air moves through the fill, small droplets of chulled water become entrained and can exit the CT as carry-over or drift. Devices called drift eliminators remove carry-over water droplets. CT drift becomes annoying when the droplets fall on people and surfaces downwind from the CT. Efficient drift eliminators virtually eliminate drift from the air stream.
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