The purpose of a cooling tower is to reject the unwanted heat from the condenser water loop of a building or process. The condenser water leaves the condenser of the chiller at around 32°C (89.6°F) and the pump sends this up to the cooling tower.
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 system has been designed so that the condenser water leaving the cooling tower and re-entering the chiller condenser, must be around 27°C (80.6°F) in order to be able to pickup enough heat on it’s next cycle.
Open (Wet) vs. Closed (Dry)
Open or wet cooling towers are the most efficient way to reject heat from the cooling system because the water evaporates to carry the heat away. This results in a loss of water from the cooling system and so it is not suitable for all locations and system designs.
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 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.
Key Concepts
- Warm condenser water enters top of tower from chiller condenser loop.
- Cool air is pulled into bottom of tower by exhaust fan mounted above tower.
- Warm condenser water is diffused down through tower, is sprayed and run packaging (thin film fins).
- Cool air is pulled through diffused water, heat transfer occurs and exits the exhaust fan.
- Cooler condenser water collects in the basin at the bottom of the tower and returns to chiller condenser loop.
- Drift eliminator collects evaporated water and reduces water loss in loop.
- Basin level monitor and overflow maintains water level.
- Water contains salts, bacteria, etc. that will collect in basin and needs to be refreshed.
