Cooling towers are common components of centralized cooling systems. Cooling towers are used either in conjunction with water-cooled chillers for chilled water systems or with plate and frame heat exchangers for water source heat pump systems.
Cooling towers are used for HVAC applications in conjunction with water-cooled HVAC equipment to cool water by exposing it either directly or indirectly to the ambient air.
Cooling towers that expose the cooling water directly to the ambient air are called open cooling towers. Those that expose the cooling water indirectly to the ambient air are called closed-circuit cooling towers
For open cooling towers, the water circulating through the water-cooled equipment is the same water that is circulated through the cooling tower; this water is in direct contact with the ambient air. Thus, for open cooling towers, the cooling water system is an open system.
For closed-circuit cooling towers, the water circulating through the water-cooled equipment is circulated through a separate heat exchanger coil mounted within the cooling tower. This water is not in direct contact with the ambient air. Water circulated within a separate open system within the cooling tower is in direct contact with the ambient air and is sprayed over the heat exchanger coil. Thus, for closed-circuit cooling towers, there are two separate cooling water systems: the closed system,41 which circulates water through the water-cooled equipment, and the open system, which circulates water through the cooling tower and is sprayed over the heat exchanger coil