The counterflow mechanical draft tower occupies less floor space than a crossflow tower but is ___________ for a given capacity.

The reason the counterflow mechanical draft tower is taller for a given capacity compared to a crossflow tower is primarily due to its design and operational efficiency. In a counterflow design, air moves upward through the tower while the water flows downward. This vertical arrangement allows for more efficient heat and mass transfer between the air and water, enabling the cooling process to occur more effectively.

Since the cooling tower is designed to maximize this interaction in a smaller footprint, it compensates for the reduced horizontal space by extending vertically to achieve the necessary cooling capacity. As a result, the height of the counterflow tower is greater, reflecting the need for a longer vertical path to ensure adequate contact time between the air and water, which facilitates heat exchange.

In contrast, a crossflow tower, where the air moves horizontally and the water falls vertically, utilizes its layout to spread out over a larger footprint. This design allows for a lower structure since it can use a larger floor area to accommodate the same cooling capacity. Hence, for a given capacity, it is typical for counterflow towers to result in a taller structure.