An induced draft cooling tower uses a fan mounted at the top to pull air upward through the tower, creating negative pressure that draws water down over the fill media. The rising air and falling water create a counter-current heat exchange that effectively removes heat from the water. This design is the most common type used in commercial and industrial HVAC systems.
Technical Details
Induced draft towers operate with fan speeds typically between 800-1,200 RPM, powered by electric motors ranging from 5 to 200 horsepower depending on capacity. The fan draws ambient air in through the sides and discharge plenum, creating velocities of 5-8 feet per second through the fill media. This configuration allows for taller towers without excessive motor load, enabling better heat transfer efficiency compared to forced draft designs.
Operational Advantages
These towers provide superior heat rejection capacity and flexibility in variable load conditions. The induced draft design minimizes motor and gear box noise by positioning them away from the air inlet, and allows better distribution of water across the entire fill area. Maintenance access is typically easier since the fan sits atop the structure. They achieve approach temperatures within 3-5 degrees of wet bulb temperature in optimal conditions.