Exergy analysis of a novel inlet air cooling system with gas turbine engines using cascaded waste-heat recovery

In this work, an innovative sustainable energy efficient system is dealt with cascaded waste-heat recovery system (CWHRS). It is composed of a gas turbine (GT) engine, where the heat was recovered from exhaust gases in an upper propane ORC cycle which produces power from the first expander. This heat is further recovered in another lower propane gas refrigeration cycle, where the most important target is cooling the ambient intake air of the GT engine. Thus, engine power is boosted and thermal efficiency is improved. An exergy analysis is carried out, where the primary objective is to analyse each component and overall system, hence determining where the major losses of exergy occur. Many operating variables are taken into consideration: namely, inlet temperature of expander 1, turbine inlet temperature, pressure ratio for the GT, upper and lower propane cycles. The analysis shows that at design point the overall exergy efficiency and destruction are 37% and 95,952 kW, respectively. Moreover, the highest amount of irreversibility occurs in the combustion chamber due to the high temperature difference in the chemical reaction. The optimisation analysis reveals best exergy efficiency with about 40%.