How do cooling towers cool water?

Question

by a process condensation, evaporation or compression?

Answer 1

I believe the cooling towers just store water.  From them the water is piped to where it is needed to cool the reactor, then sent back to the towers to allow that heat to radiate into the air and allow the water to cool for reuse.

Answer 2

There are two places where water is used in a cooling tower, one a closed-cycle loop and the other open.  The closed-cycle is hot water in tubes flowing through the cooling tower.  Water from a separate source is sprayed on the tubes.  The water on the outside of the tubes evaporates, and the heat it takes to evaporate all that water cools the water in the tubes, whereafter it returns to where it is needed for cooling.  

The link below has a lot more detail on the process, which I have elided to the point of incomprehensibility.