Choice of a reference state for exergetic analysis

The concepts of thermomechanical exergy, chemical exergy, restricted dead state, and unrestricted dead state are described. A detailed discussion is presented on identification of the reference state. The influence of commonly-used methods on evaluation of the overall exergy is analysed. The effect of using a standard reference state is compared with that for a reference state in which the composition is defined according to the problem under study. Finally the second-law efficiency is defined and discussed for general control volumes and closed systems.