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Types of Cooling Towers

There are two basic types of cooling towers, direct (or open) and indirect (or closed).

Direct (or open) Cooling Tower

Picture of a direct (or open) cooling tower - Illustration recreated for web by Technologists Inc. using graphic supplied by Washington State University Cooperative Extension Program to PNL, for use with FEMP O&M Best Practices, as a model. - Click to enlarge.

Direct (or open) cooling tower—Click image to enlarge and view reference

This type of system exposes the cooling water directly to the atmosphere. The warm cooling water is sprayed over a fill in the cooling tower to increase the contact area, and air is blown through the fill. The majority of heat removed from the cooling water is due to evaporation. The remaining cooled water drops into a collection basin and is recirculated to the chiller.

Indirect (or closed) Cooling Tower

An indirect or closed cooling tower circulates the water through tubes located in the tower. In this type of tower, the cooling water does not come in contact with the outside air. This represents a "closed" system.