In cross flow towers, air flow is directed across the water flow. Air flow enters the vertical faces of the tower to meet the fill. Hot water is distributed to the fill, perpendicular to the air flow, by gravity through perforated basins. The air passes through the fill, past the water flow into an open area while gravity distributes the water through nozzles across the fill. The turbulent air will flow through the fill structure to maximize the contact with the water thus drawing heat out of the water. A cold water basin contains the water after its interaction with the air flow.
In counter flow towers, air flows opposite to the water flow. Air enters the tower beneath the fill and is drawn up vertically into the tower. Above the fill, hot water is introduced through low pressure spray nozzles to divide the hot water over the surface of the fill in fine droplets. The cooling air draws heat from the water as it progresses to the bottom of the tower. The drift eliminator above the spray nozzle captures water droplets and returns the water to the circulating system. A cold water basin contains the water after its interaction with the air flow.