Induced draft cooling tower is also known as mechanical draft cooling tower that use one or more fans to drive or draw air through flowed water. Incoming water is injected throughout the tower with a spray distribution header which is directed downwards in order to maximize the contact of water and air. Since the airflow is counter to the water flow, the coolest water is found at the bottom is in contact with the driest air while the warmest water found near the top of the tower in contact with moist air, resulting in increased heat transfer efficiency.
Types of Induced Draft Cooling Tower
- Counter flow induced draft
- Counter flow forced draft
- Cross flow induced draft
Counter Flow Induced Draft
In counter flow towers air flows vertically upward, counter to the flow of falling water in the fill. Due to this vertical airflow, it is not possible to use the open, gravity flow basins typical in crossflow designs. Instead, counterflow towers use pressurized, pipe-type spray systems to spray water onto the top of the fill. Since air must be able to pass through the spray system, the pipes and nozzles must be farther apart so as not to restrict airflow. In this type of towers fans are mounted on top of the unit and pull air through the fill media.
Counter Flow Forced Draft
This type of tower is similar to counter flow induced draft cooling tower, only difference is that air is pushed by blowers located at the base of the air inlet face.
Cross Flow Induced Draft
In crossflow towers the water flows vertically through the fill, while the air flows horizontally, across the flow of the falling water. Because of this, air does not 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 applied on all crossflow towers.