Quantification of irreversibilities in practical cyclic processes using exergy analysis and Gouy-Stodola theorem

The exergy analysis of a process to quantify the irreversibilities is advantageous over the entropy analysis in that it provides the definition of efficiency of a process, referred to as exergetic efficiency (defined as the ratio of exergy recovered to exergy supplied to the process). Unfortunately, the exergy analysis of practical multi-unit cyclic processes is rarely covered adequately in the undergraduate courses in engineering thermodynamics. In this article, the quantification of irreversibilities is illustrated in detail for a practical cyclic steam power plant using exergy analysis and Gouy-Stodola theorem. The efficiencies are determined for the various components and for the whole process. The theoretical background related to exergy, exergy analysis, and Gouy-Stodola theorem is also covered briefly for the benefit of the students. An assessment problem dealing with vapor-compression refrigeration cycle is included at the end in order to assess the intended learning outcomes of this article. The key solution steps along with answers are also provided for the benefit of the readers. As exergy analysis involves advanced level concepts in thermodynamics, the appropriate place for the introduction of the material presented in this article is the second, advanced level, course in thermodynamics.