2 - Transport and rate processes

Abstract

This chapter summarizes nonequilibrium systems, the kinetic theory, transport phenomena, and chemical reactions. Statistical mechanics can provide phenomenological descriptions of nonequilibrium processes. An alternative approach based on kinetic theory is favorable, especially in describing the transport and rate phenomena. A kinetic theory of nonequilibrium systems has been developed for dilute monatomic gases at low pressure. Substantial progress has also been achieved in extending the theory to dense gases, real gases, and liquids. Typically, kinetic approaches start with the Boltzmann equation for the velocity distribution function of each component in a multicomponent system, and the time evolution of the distribution function is obtained by solving the governing kinetic equations with a set of initial conditions. Evolution of the velocity distribution function with time is calculated with an external force acting on a molecule and using an intermolecular potential energy function, such as the Lennard–Jones potential. The kinetic theory leads to the definitions of the temperature, pressure, internal energy, heat flow density, diffusion flows, entropy flow, and entropy source in terms of definite integrals of the distribution function with respect to the molecular velocities. If the collisions of molecules produce a chemical reaction, the Boltzmann equation is modified in obtaining the equations of change.