Cooling or cooling towers are equipment used to cool a flow of water, heated in the process of transferring thermal energy rejected in an industrial process, from its point of origin to the environment. This cooling is mainly achieved by evaporation of part of this water flow.
In towers that work with the natural movement of the air, it circulates inside it horizontally, while the water is sprayed and dripped or sprayed on a filling that may be wood, plastic, or ceramic material. In towers where air circulation is forced, a centrifugal fan blows the air under pressure, backwashing with the direction of waterfall. When the fan is placed on top of the tower to prevent the recirculation of hot humid air there is what is called an induced air tower.
Water spraying ensures the formation of a large exchange surface with air flowing inside the tower. Heat is transferred to the air by increasing its dry bulb and wet bulb temperatures and their moisture content. Evaporation of a small portion of the water stream then cools the water.
A common tower configuration in large-capacity thermoelectric power plant applications is that of a hyperbolic shape, reminiscent of a 50 to 100m high chimney where air flow occurs by natural convection.
In general, the towers work with temperature differences of the water flow to be cooled, in the order of 5.5 ° C, between 35 ° C at the inlet and 29.5 ° C at the outlet.
In addition to evaporation losses, about 2% of the volume circulating through the tower, there are also drag losses, which can reach 1% of this volume and blow down losses. These vary depending on the amount of salts dissolved in water and result from the need to reduce their concentration, increasing with evaporation, mainly CaC03, to prevent their precipitation on the exchange surfaces, isolating them and drastically reducing the capacity of these salts. heat transfer thereof.
The lost water volume is continuously replenished to maintain the full cooling volume.
This water consumption can be an important limitation to the application of an industrial process, especially in regions where water supply is restricted and / or extremely costly.
