If you look at the roof of most high rise commercial buildings, or even around industrial sites and power stations, you’ll notice these large boxes with a fan on top. These are Cooling Towers and their purpose is to reject the unwanted heat from a building or process.
To help understand how Cooling Towers work, let’s look at an example of a typical, common Cooling Tower found on a city office type building.
These Cooling Towers are known as “open” or “wet” Cooling Towers because the water in the pipework leaves the pipe (system) when it is sprayed inside the cooling tower, purposely soaking the inside of the tower to cause evaporation and heat loss. Water will be able to leave this circuit so it is referred to as “open” and the spray of water to soak the inside of the tower is why it is referred to as “wet”.
You can also find “closed” or “dry” cooling towers. This type does not spray the condenser water and the water stays within a sealed pipe at all times. Therefore water can not leave the system and it is known as a “closed” type.
The Cooling Tower receives warm water from the chiller at a temperature, for example, of 32°C (89.6°F). This water is known as the condenser water because it picks up it’s heat in the “condenser” of the chiller.
The Cooling Tower must cool this water down to around 27°C (80.6°F) so that it can return to the chiller and pickup more heat.
Basic understanding of how they work.
When the warm condenser water enters the Cooling Tower, it is sprayed into small droplets across the “fill packaging” this increases the surface area of the water and allows for greater heat loss.
The fan on top of the Cooling Tower sucks air in from the bottom of tower, and moves it up and out the top of the unit. In the opposite direction that the warm condenser water is flowing. This air will carry the heat away, out of the Cooling Tower and into the atmosphere.