Abstract
In this article, a novel method of inlet air cooling is proposed to enhance the performance of a gas turbine operating in hot climates. The intake air at the compressor bell-mouth is cooled by an air Brayton refrigerator driven by the gas turbine, and the refrigerator uses air as the working fluid. Introducing the air refrigeration cycle provides the advantage of quite low temperatures close to 0 degrees C and even lower. This is not possible with other methods of intake air cooling, namely evaporative cooling or use of waste heat-driven absorption machines. A thermodynamic analysis through energy and exergy is employed, and a comprehensive parametric study is performed to investigate the effects of extraction pressure ratio, extracted mass rate, turbine inlet temperature (TIT), and ambient relative humidity (RH) on increase in net work output, first law efficiency, and second law efficiency of a compressor inlet air-cooled gas turbine cycle using a Joule-Brayton refrigerator. The analysis of the results indicates that the maximum exergy destroyed in the combustion chamber, which represents > 80 per cent of the total exergy destruction in the overall system, is significantly affected by the extraction pressure ratio and TIT and is slightly affected by ambient RH. The increase in the net work output, the first law efficiency, and the second law efficiency of the cycle significantly varies with a change in the extraction pressure ratio, extraction mass rate, TIT, and ambient RH. Results clearly show that performance evaluation based on first law analysis alone is not adequate, and hence more meaningful evaluation must include second law analysis. Decision-makers should find the methodology presented in this article useful in comparison and selection of various methods for inlet air cooling in gas turbines.