A forced draft cooling tower uses a fan mounted at the base to push air horizontally or upward through the tower fill media and falling water. The pressurized air stream forces contact between air and water droplets, rejecting heat as water cascades downward. This design occupies less vertical space than induced draft towers, making it suitable for rooftop installations.
Technical Details
Forced draft towers employ centrifugal or axial fans that discharge air at velocities of 6-12 feet per second into the fill media. The fan motor and drive mechanism are located at ground level, requiring 10-75 horsepower depending on capacity. These systems typically achieve approach temperatures within 5-8 degrees Fahrenheit of the wet bulb temperature, performing adequately in most climates.
Design Considerations
The horizontal air discharge creates potential issues with recirculation of warm discharge air back into the intake, particularly in calm conditions or on congested rooftops. The pressurized design requires more robust structural support and higher motor power consumption than comparable induced draft units. Forced draft towers work effectively in areas with strong prevailing winds that prevent warm air recirculation. They are commonly found in smaller commercial systems and packaged rooftop units due to their compact height and space efficiency requirements.