3.1 Assessing the Benefits of Inlet Air Cooling

The benefit and desire for combustion turbine inlet air cooling stems from the desire to increase turbine-generator capacity and, possibly, decrease the heat rate. A typical inlet air temperature desired is near 40 F (4.4 C), though this temperature varies. Some aeroderivative engines attain maximum capacity at higher temperatures. The relative effectiveness of CTIAC has been addressed by Kitchen and Ebeling (1995) by taking the ratio of the change in enthalpy of the air cooled from the ambient condition to the desired inlet condition, m _a ?h _a, and the increase in generation capacity, ?Wo.

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The value of inlet cooling is comparatively easy to assess as the cost of cooling is approximately proportional to the cooling load. The inverse of the effectiveness is the ratio of the relative benefit to the relative cost of cooling the air. Defining the relative performance (or a coefficient of performance) as the inverse of effectiveness as

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the greater the value of PI, the greater the relative enhancement of turbine-generator capacity, which corresponds to smaller values of E. A list of some combustion turbines with operating characteristics and values of E and PI are given in Table 1 (Kitchen and Ebeling 1995). It should be noted that the effectiveness values given represent the capacity improvement potential for a specific combustion turbine at the indicated inlet air temperature. Lower "effectiveness" values generally represent ISO higher-efficiency combustion turbines and, therefore, the...