Thermodynamics is an attractive field of science concerned with the energy and work of a system, and this branch of physics has long been a crucial part of engineering programs worldwide. Thermodynamic application is widespread to such fields as macroscopic organisms to public domestic appliances. With different chapters included in this book, students and engineers will gain an understanding of the concepts and definitions, necessary background and importance of the subject of thermodynamics. They will be able to apply the basic terminology, principles and theories in order to analyze and evaluate various thermodynamic cycles used for the production of energy, heat, and work within the natural limits. This book would be suitable to both university students and engineers. It can be used as a university textbook and guide to the numerous technologies in the electric power industry. We have taught this subject for several years and we are aware of the lack of suitable texts and references available for students and engineers. We believe that this book represents a fundamental assistance to that community and that it will be considered the standard work in the area.