A secondary fluid cooling (SFC) process is also shown in Figure 10, where the air-water vapor mixture is being cooled from the same initial condition, condition 1. The SFC fluid process decreases the enthalpy (and temperature) of the air-water vapor mixture as the mixture is cooled. The water vapor content (the humidity ratio) remains constant as the mixture decreases in temperature to condition 8,73.5 F (23.1 C). Continued cooling will follow the cooling coil performance curve. If cooled to 40 F (4.4 C), the condition is shown as condition 9. Condition 9 represents a mixture where the relative humidity of the air is near 100% with a decreased humidity ratio, having forced part of the water vapor to condense out from the mixture.

This process entails concerns regarding the possibility of liquid water drops carried into the turbine that may have not evaporated. An overspray system uses additional water beyond that required for inlet air cooling to cool the air in the first stages of the compressor and to increase the air mass flow rate (Nolan and Twombly 1990).

A water wash system, where the air is directed through a spray or falling film of chilled water or fluid, undergoes both sensible and latent cooling, a nonadiabatic cooling process, as discussed later.