Energetic and exergetic performance analyses of a combined heat and power plant with absorption inlet cooling and evaporative aftercooling

In this paper, exergy method is applied to analyze the gas turbine cycle cogeneration with inlet air cooling and evaporative aftercooling of the compressor discharge. The exergy destruction rate in each component of cogeneration is evaluated in detail. The effects of some main parameters on the exergy destruction and exergy efficiency of the cycle are investigated. The most significant exergy destruction rates in the cycle are in combustion chamber, heat recovery steam generator and regenerative heat exchanger. The overall pressure ratio and turbine inlet temperature have significant effect on exergy destruction in most of the components of cogeneration. The results obtained from the analysis show that inlet air cooling along with evaporative aftercooling has an obvious increase in the energy and exergy efficiency compared to the basic gas turbine cycle cogeneration. It is further shown that the first-law efficiency, power to heat ratio and exergy efficiency of the cogeneration cycle significantly vary with the change in overall pressure ratio and turbine inlet temperature but the change in process heat pressure shows small variation in these parameters.

► Application of exergy analysis along with energy analysis of gas turbine cogeneration is essential in order to observe its complete thermodynamic view.
► We adopt absorption inlet cooling along with evaporative aftercooling in gas turbine cogeneration which results in significant performance improvement.
► Analysis of the results concluded that the major option to improve the global thermal efficiency of gas turbine cogeneration is to reduce the local irreversibility rates in the combustion chamber.
► Evaporative aftercooling along with absorption inlet cooling results in higher optimum pressure ratios.
► It is recognized that experimental studies are needed to establish the practical usefulness of this proposed cycle.