Exergetic analysis of a natural gas-burning steam power plant

An exergetic analysis of the main subsystems of a steam power plant was undertaken. The product of the entropy generation rate and the effective temperature (modified Gouy–Stodola law) was used to calculate the real power/exergy loss due to various irreversibilities present in the subsystems. The use of the effective temperature was deemed appropriate because its derivation depends on the dynamics of the subsystem(s) under consideration. The results of our analysis showed that the highest rate of entropy generation occurred in the condenser while the maximum rate of entropy generation for the feed-water heaters was observed in the Heater6. The reasons for these observations were discussed in the relevant sections of this study. The greatest power/exergy loss was observed in double-flow low-pressure turbine. This could be due to the fact that the inlet steam was split and flows axially in opposite directions through the turbine blades, thereby creating a lot of irreversibilities. According to the results of this study, it can be concluded that the most irreversible unit in the system is the condenser with (Formula presented.) loss and followed by the high-pressure turbine with a power/exergy loss of (Formula presented.). It was observed that when environmental temperature was used in the calculation of power/exergy loss, the results always underestimated the real power/exergy loss. Finally, the results of this study have highlighted the areas where the various subsystems of the power plant can be improved. The analyses show where the largest quantities of power/exergy loss are being dissipated within the plant, thus pointing to areas where improvement in energy usage can be made. The use of exergy as a potential design and retrofit tool was also pointed out. © 2016 Engineers Australia.