The thermodynamics of flow is based

The thermodynamics of flow is based on mass, energy, and entropy balances, which have been
developed in Chaps. 2 and 5. The application of these balances to specific processes is con-
sidered in this chapter, The discipline underlying the study of flow is fluid mechanics,' which
encompasses not only the balances of thermodynamics but also the linear-momentum principle
(Newton's second law). This makes fluid mechanics a broader field of study. The distinction
between thermodynanzics problems and juid-mechanics problems depends on whether this
principle is required for solution. Those problems whose solutions depend only on mass con-
servation and on the laws of thermodynamics are commonly set apart from the study of fluid
mechanics and are treated in courses on thermodynamics. Fluid mechanics then deals with
the broad spectrum of problems which require application of the momentum principle. This
division is arbitrary, but it is traditional and convenient.