The purpose of this book is to lay the groundwork for the analysis and the design of processes with a view to energetic efficiency. Energetics is used in the original sense of the engineer W. J. M. Rankine (Proc. Roy. Philosoph. Soc. of Glasgow III, 381 [1955]) and the physical chemist J. N. Br\3nsted (Principles and Problems in Energetics, Interscience, New York, 1955), i.e., the macroscopic description of the flows of different forms of energy, and the general laws governing the mutual transforma tions of these flows. The prerequisite for the use of the book is a conventional course in equilibrium thermodynamics as usually taken in the junior (third) col lege year. The author believes that while knowledge about equilibria is essential, most engineers and many scientists are mostly interested in systems in which equilibrium has not yet been reached. In such systems, flow phenomena such as heat, mass and electricity transfer, as well as chemical reactions, can take place, and it is important to know the driv ing forces and laws governing the interactions of these flows.