Cooling Towers Use and Theory
In HVAC environments towers are typically used to remove heat from a chiller:
- Hot water from the chiller is sent to the top of the cooling tower where it is released into the tower.
- The water is sprayed down to the basin or through a heat exchange.
- During this process, it is exposed to airflow that is forced, induced, or naturally drafted into the tower.
- The exposure to the ambient air converts the hot water into vapor, while the remainder of the water falls towards the basin at the bottom where it is recycled to the chiller.
- The vapor is pulled outside via fans at the top of the cooling tower, and supplemental water is added to replace what was lost during the process.
Evaporative cooling is the process of transferring heat by using water and airflow. This process can use air to cool hot water, or water to cool hot air, depending on the need. In principle, airflow passes through a heat exchange, a pipe or cellulose material saturated with water, transferring heat away from one medium to the other. The dissipation of heat results in water vapor, which is expelled from the process.
Evaporative cooling is effective at cooling air using the same process. Evaporative cooling for airflow can either be direct or indirect. Direct evaporative cooling involves a source of air, a heat exchange, water, and a motorized fan.
- Water is brought up from the basin and saturates the heat exchange.
- Air is brought into the system and passes through the heat exchange, cooling the air and creating water vapor.
- The vapor is pulled out, and the motorized fan directs the cooled air out of the system and towards its intended location.
- Indirect evaporative cooling sends a secondary airflow perpendicular to the primary one through the heat exchange and out the exhaust vent.
- The primary airflow is further cooled by the secondary airflow.
- Supplemental direct evaporative cooling processes can be added to continue lowering the temperature of the primary airflow.