What is the temperature of the water leaving a well-operating induced-draft cooling tower?

The correct answer is that the temperature of the water leaving a well-operating induced-draft cooling tower is at the wet-bulb temperature of the air. This is because cooling towers function based on the principles of heat exchange and evaporation.

In an induced-draft cooling tower, water is distributed over a falling film or splash pack where it interacts with air that is drawn through the tower. As water evaporates, it absorbs heat from the remaining water, which lowers the temperature of the water that's circulating through the system.

The wet-bulb temperature reflects the temperature of the air after moisture is accounted for and is indicative of the cooling potential due to evaporation. The cooling tower operates most efficiently when the water temperature approaches the wet-bulb temperature of the surrounding air. Thus, the water leaving the cooling tower will be at this temperature, as it is the point where maximum cooling can occur under the given conditions.

While other temperature concepts like ambient, dew point, and dry-bulb temperatures are related to atmospheric conditions, they do not accurately describe the water’s temperature as it exits a cooling tower.