I am doing a project on developing a code for the first and second law analysis of the Brayton Simple and Modified cycles. The first law part is simple. But I have run into a roadblock when I started the second law part. In the book on thermodynamics by Cengel and Boles, where he has performed the exergy analysis for the Otto cycle, he has mentioned that exergy destruction takes place only when irreversibilities exist and hence the heat addition processes, that take place through a finite temperature difference, have exergy destruction associated with them. Now in the modified Brayton Cycle with an exhaust heat exchanger, does exergy destruction occur in the exhaust exchanger by the same logic?
In any real Gas Turbine Cycle, exergy destruction takes place in each every component, be it the Turbine, Compressor or Exhaust Gas Heat Exchanger. In the analysis of the Otto Cycle in Cengel and Boles, he has performed the exergy analysis on an ideal cycle. Additionally, to perform exergy analysis on any component, the simple exergy balance equation needs to be employed as:
WorkTransfer = (Chemical Exergy) + (Exergyin) - (Exergyout) - (ExergyDestroyed) - (Heat Supplied/Temperature of heat supply)