Because of the way the water enters the tower it isn’t possible to use the flow of gravity. The air is pushed upwards vertically, so it is “counter” to the water flow which is flowing vertically down. The pipes and nozzles within the distribution system must be carefully positioned to ensure airflow goes unrestricted. The air and water flows are effectively opposite to each other – hence the name of the design.
The air enters the counterflow cooling tower underneath the fill media and is taken up in a vertical fashion, it is pushed or sucked by the fan at the top of the tower. The process water sprayed from near the top of the tower flows downwards into the fill, but opposite to the air flow. The cooled water collects in a basin at the bottom of the tower, as with a crossflow design tower and the air is discharged from the top of the tower. Similarly, it’s the interaction of the water and air flow that causes evaporation and achieve the cooling effect needed.