Exergy Analysis of Combined Effect of Evaporative Cooling and Steam Injection on Gas Turbines Performance Enhancement in Hot and Humid Climates

Abstract

Abstract:In this paper, an exergy analysis has been used to examine for a combination of cooling the compressor intake air and inject steam in the combustion chamber the performance enhancement of gas turbine power plants using by a combination of intake air cooling the compressor intake air and injecting steam in the combustion chamber is studied. The limits of the cooling capability of an evaporative cooler are analyzed and formulated in terms of the characteristic dimensionless groups: the temperature ratio (ξ T ), the power gain ratio (PGR), Thermal efficiency change (TEC) and humidity ratio (RH). Similarly the effect of steam injected is presented as a ratio (y) of total volumetric flow rate. The effect of different pressure ratio (PR) is examined for Saudi Arabia summer weather when the turbine inlet temperature, T 3 , is a predetermined of 1373.15 K. The results for a specific example where the air evaporative cooler drops the temperature to the wet bulb temperature is presented and show the power gain ratio enhancement depends on the ambient temperature, relative humidity, evaporative cooler effectiveness and slightly on the pressure ratio. The results indicate for PR =10, the PGR is enhanced by 9% at 20% relative humidity and drops to 3.37% at 60% relative humidity. The daily performance of the cooling method is examined for the hot humid conditions of Jeddah, Saudi Arabia. The results show that the evaporative cooler increased both the daily power output and the thermal efficiency by 2.52% and 0.112% respectively. In addition, the result shows that the combustion irreversibility is the dominant in the governing the system PGR and TEC with various steam injection ratios for PR=10.