2.3 Air Cooling System Equipment

The air entering a combustion turbine can be cooled by different methods and by a wide range of equipment types. Historically, air cooling has been accomplished by evaporative cooling with wetted media, secondary fluid cooling with cooling coils, using chilled water from ice storage, or direct refrigerant cooling using evaporator coils. Evaporative cooling using treated water is relatively inexpensive, but the decrease in inlet air temperature is limited to approaching the ambient saturated wet-bulb temperature. As such, evaporative cooling is most advantageous in drier climates where the required water supply is not limited.

Chilled water inlet air cooling `using water-chilling refrigerating equipment, with or without ice or chilled water storage, allows greater decreases in turbine inlet air temperature than evaporative cooling, a greater increase in generation capacity, and a greater decrease in heat rate. The choice of the most appropriate CTIAC air-cooling equipment is economically driven, considering the required turbine capacity and the associated required equipment and fuel costs, climate, heat rate decrease, turbine and cooling equipment operating hours, and the values of steam, electricity, source water, and condensate water. Some of the characteristics of the cooling equipment and typical applications are discussed below.