Free Cooling Systems
A free cooling system reduces energy use by using a fluid cooler or cooling tower to cool the process fluid in place of a chiller. The free cooling source is commonly a fluid cooler but a cooling tower may be used. The free cooling source may be dedicated to free cooling or could be the primary cooling source with a dual or dynamic set point that changes based on the outdoor air temperature. It can use either use a dynamic or static set point and can be isolated from the process fluid circuit with a heat exchanger, or can be in a common fluid circuit with the process fluid.
Isolated Source System
In an isolated source system, a heat exchanger isolates the process cooling system from the free cooling system. This allows the use of a glycol solution as the cooling source and/or to protect the process fluid from contamination from the cooling source. In cases where a fluid cooler or adiabatic fluid cooler with a glycol solution is the cooling source, the heat exchanger isolates the process fluid from the glycol solution to allow water to be used in the process loop. In cases where a cooling tower is the cooling source, the heat exchanger provides protection of the process fluid from possible contamination from the cooling tower water.
Isolated Source Free Cooling Circuit Diagram
Common Source System
In a common source system, the process cooling system and the free cooling system share a common fluid. The common source free cooling system is typically only used when there is a dedicated fluid cooler in line with a chiller, designed to run during cooler weather conditions, where the ambient air is able to provide a portion or all of the process cooling. These systems typically use a glycol solution as the cooling fluid due to prevent freezing in the fluid cooler during winter operation.