Water returned to a cooling tower to be cooled most likely enters...

In cooling towers, the design is such that the warm water from the system is typically directed to the top of the tower, specifically at the "hot deck." This is because the cooling process relies on the gravitational flow of water from the top, allowing it to distribute evenly across the fill material within the tower. As warm water enters at the top, it spreads out and comes into contact with the cooler air that is drawn in from the bottom. This maximizes the surface area for heat exchange between the water and the air, facilitating effective cooling.

The significance of this design is that it promotes efficient cooling and prevents stagnation of warm water, which could otherwise lead to issues like increased temperatures and the potential for Legionella growth. The placement at the top allows for the greatest interaction with airflow, which is essential in maintaining optimal cooling tower performance.