Cooling Towers seem pretty self explanatory when you listen to their name, but there is a lot more complexity than indicated by their simple moniker. Complex both in function and deployment, cooling towers are fascinating machinations that synthetically recreate a natural phenomenon, evaporation.
The core function of cooling towers is to extract heat from heated water and disperse the extracted to heat into the surround environment outside of the tower. This evaporative process is maximized when as much air as possible flows over as much water surface as possible. There are different methods of heat extraction as well as several types of cooling towers that are used depending on where the facility is and what it is used for.
Two very common types of cooling towers are crossflow and counterflow towers. Crossflow towers use splash fills to expose descending water to air flowing across is at is falls in order to extract the heat. Counterflow towers the air is moved upward against the downward flow of the descending water as opposed to across the water in order to achieve the same heat extraction. While these are the two most common types of cooling towers there are definitely more styles that are used.
Mechanical and Natural Draft are two styles that are used as alternatives to cross flow and counterflow. Mechanical draft towers use mechanized methods to push the air across the water, usually in the form of fans. The mechanized components can vary, but they ultimately serve the same purpose. Natural draft towers are tall and chimney like and use the buoyancy of heated air to provide the flow of air over the water. These are the iconic looking towers often seen on nuclear sites. Their shape promotes the natural flow of warm air out of the top of the tower.