There are many important systems that exhibit nonequilibrium or noncontinuum behavior. This final chapter examines some important examples of such systems. In doing so, we have two objectives. The first is to understand how, and under what conditions, the system behavior may deviate from the idealizations embodied in equilibrium theory or continuum theory. The second is to demonstrate theories and methods that are commonly used to model nonequilibrium and noncontinuum systems. Because they are commonly used to analyze such systems, kinetic theory and the Boltzmann transport equation are introduced. Nonequilibrium and noncontinuum phenomena associated with multiphase systems and electron transport in solids are examined in detail. The final section of Chapter 10 uses results from previous chapters to examine length scales and time scales at which classical and continuum theories become suspect. Doing so defines the range of conditions for which we expect classical and continuum theories to be accurate models of real physical systems. Although limited in its coverage, this chapter provides an introduction to microscale aspects of nonequilibrium and noncontinuum phenomena and serves to illustrate how they relate to the theoretical framework developed in the preceding chapters.

Basic Kinetic Theory

With increasing frequency engineers are dealing with microscale systems in which the applicability of classical macroscopic equilibrium thermodynamics becomes questionable. Generally, the applicability of classical equilibrium theory breaks down because the system is far from equilibrium and/or the system behavior deviates from a continuum model.