How do shoreline nuclear facilities lower the temperature of wastewater generated by their cooling systems before it enters the ocean?
One way is to use massive pond systems for evaporate cooling.
Turkey Point nuclear plant. Closed loop system explained here - https://youtu.be/qt9dtYC7RDE
In heat exchanger design, typically a maximum rise is specified by the end user - be it the environmental control groups, or the plant designer itself. The heat exchanger is then designed to remove the required amount of heat, which is known, by having the output have a certain temperature fall of the first stream, and a maximum temperature rise. The actual temperatures are then simulated in various selected heat exchangers, until a desired heat exchanger that matches the constraints is determined. Usually this comes with a desired flowrate on both the hot line and the cool line. The cool line flowrate would usually be a minimum to remain open, and conservatively additional flow would be designed into the system (larger pumps, larger pipes, etc).