Engineering Thermodynamics - Concepts and Laws

An Informal Presentation

Abstract

The structure of these notes is as follows:

The first chapter presents the fundamental concepts. This chapter should not be dismissed as mere review or philosophical preamble; it constitutes the essential foundation of thermodynamics. I urge you to pause and reflect on each concept and definition, critically engaging with the material and even considering alternative formulations.

Chapter 1 establishes a critical foundation for subsequent material by rigorously defining the thermodynamics system and detailing the treatment of its properties under equilibrium conditions.

Building upon this foundation, Chapters 2 and 3 provide a detailed elaboration of the concepts of work and heat, the two fundamental modes of energy transfer.

The core laws of thermodynamics are introduced beginning in Chapter 4. This chapter covers the Zeroth Law and the principle of thermometry. In Chapter 5, based on the First law of thermodynamics, a new system property—internal energy—is derived, utilizing concepts established in the preceding chapters. Moreover, another form of energy—enthalpy—arises when applying the first law of thermodynamics to open systems. Consequently, a separate section is devoted to this topic.

Chapter 6 explains the pivotal distinction between reversible and irreversible processes. This sets the stage to introduce the Second Law of Thermodynamics explained in chapters 6 to 8.

Chapter 9 reflects the authors’ personal understanding of entropy. It should be read with caution, as its contents may be controversial.

Exergy—defined as the available work or the available energy to do work with respect to a dead state—is intentionally not covered in this note. First of all, Exergy is not itself a fundamental law; rather, it is a derived concept from the first and second laws. Second, applying the exergy concept requires an understanding of optimization in energy systems under specific constraints such as cost, sustainability, and other factors. Consequently, a dedicated field known as exergoeconomics formally studies the application of exergy.

This note focuses on the basic concepts and laws of thermodynamics, with applications primarily in the domains of engineering majors such as mechanical and chemical engineering.

Finally, to ensure a clear and paced presentation, key historical developments that contributed to the unified understanding of thermodynamic laws are included in the appendices. A thorough review of this supplementary material is highly recommended for a deeper and more complete mastery of the subject.

Note that each chapter builds upon the preceding material and readers with moderate exposition to Thermodynamics are encouraged to revisit earlier chapters whenever difficulties arise.

Formal references have been intentionally omitted, as this document is not a formal textbook.

Finally, the reader may find the tone of the manuscript rather philosophical, yet its purpose is to insist on the logical arguments required to explain or prove the concepts. Logic, of course, is a branch of philosophy. Moreover, the style of the manuscript resembles that of an oral lecture. This is, of course, a deliberate choice by the authors.

The authors acknowledge that this note may contain inaccuracies or address controversial issues, and welcome feedback and error notifications.