Exactly. A car is a closed loop system. Coolant (which is water with some chemicals) cools the engine, then the hot coolant flows through a radiator which tra

Exactly. A car is a closed loop system. Coolant (which is water with some chemicals) cools the engine, then the hot coolant flows through a radiator which transfers that heat to the air, and then it just keeps cycling through. If there's no leaks then no coolant is lost. The above method could be scaled up to data center levels, but is less efficient in terms of energy usage and cost. Cheaper/easier to just spray water into the air and get "free" cooling that way, as long as you have a source of free/cheap water to replenish what is lost to evaporation. I'm not a nuclear engineer either, but I assume this is what is happening inside of the big iconic nuclear stacks. That's just cooling water being evaporated off to keep it cool.