Open evaporative cooling systems represent the most popular prevailing design selected for heat rejection. They have increased in popularity as the use of once-through cooling systems has diminished.

Cooling water is used at plants for condensing steam and for product and equipment cooling. By far, the most frequently encountered open evaporative cooling system is the cooling tower which is a unit operation that provides for cooling water recovery thus decreasing water and power requirements.

We discuss the cooling tower in detail, but we are going to take a closer look at evaporation and some of the earlier evaporative cooling systems: The Cooling Pond and The Spray Pond.