This system is similar to the open-loop evaporative system in some ways. It works by taking in water, evaporating it, cooling the remaining water, and repeating the cycle. Like the open-loop evaporative system, it requires chemical water treatment, protection from freezing temperatures, and other measures to ensure that water is kept circulating and impurities aren’t allowed to accumulate.
There are important differences, however. This system uses closed-loop piping that circulates a coolant solution back and forth from the tower, but does not circulate air and water from the outside. This protects the coolant loop from external contaminants, avoiding some of the worst complications of the open-loop system. This can make chemical treatment of the water much simpler than it would be if the entire system were exposed to outside air and water.
The tower water is still exposed, however, meaning you’ll need the same chemical treatment, blowback, and basin heating systems as you would with the open-loop system. Lime scale and other complications from contaminated water can also develop in the closed-loop system.
Still, these problems are not as big of a danger with the closed-loop evaporative system. Whatever contaminants enter the tower water stay there, rather than circulating throughout the entire system. This reduces the amount of resources needed to treat the water.
A closed-loop evaporative system can save on water costs compared to the open-loop version. As contaminants from outside water do not spread as readily throughout the system, the quality of outside water is not as crucial to the system’s functioning. This can make the closed-loop system an environmentally friendly option, as well as an affordable one.