On the Gouy–Stodola theorem of thermodynamics for open systems

Abstract

The Gouy–Stodola theorem of thermodynamics is probably the most important one from an engineering point of view. It is indispensable in the analysis and design of a process from a thermodynamics perspective. It quantifies the level of irreversibility in the process. Yet, it has not received the due attention in the engineering literature. For example, the textbooks in chemical engineering thermodynamics rarely mention this theorem. This theorem can be expressed in two different ways, either in the form of exergy destruction or in the form of lost work. The conditions under which this theorem is applicable are not clearly spelled out in the existing textbooks and published literature. There is confusion in the literature regarding the general validity of the theorem. In this article, a complete analysis of this theorem is presented for open systems and its limitations are pointed out. This article should be of help to students in understanding and applying the Gouy–Stodola theorem to different practical situations dealing with flow processes. Due to its practical significance, it is important that this theorem is taught to all engineering undergraduate students regardless of their engineering discipline. As the theorem involves advanced level concepts in thermodynamics such as entropy generation and exergy destruction in the system and the surroundings, the appropriate place for the introduction of this theorem is the second advanced-level course in thermodynamics. This should not pose any problem as most engineering disciplines teach two one-semester courses on thermodynamics to the undergraduate students.