Cooling Tower Basics - Principles of Operation

Cooling towers come in many different shapes and sizes. They range from small two-ton factory-assembled models to large field-erected towers capable of rejecting thousands of heat BTUs. Although the shapes and sizes can vary, the principle of operation remains the same.

Warm water from the heat source is pumped to the water distribution system at the top of the tower. The water is distributed over the wet-deck fill by means of nozzles. Simultaneously, air is drawn through air-inlet louvers and through the wet-deck surface causing a small portion of the water to evaporate. The evaporative process removes heat from the water. The warm, moist air is drawn out of the top of the tower. The resulting cold water is then recirculated back through the heat source in a continuous cycle.
 

The internal components of the cooling tower represent the core of the heat transfer efficiency. Different models use various components to achieve the best results. However, over time the components can wear out, become fouled, or perhaps the site conditions or process has changed and the original components no longer fit the need. Tower Components offers a wide variety of cooling tower products that can be custom-selected for new and existing cooling towers. Just as a cooling tower has a principle of operation, each component has a principle of operation specifically suited to operating conditions.

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.