The concepts of thermodynamic friction, thermal available energy, chemical available energy and thermal energy

Abstract

Internal energy can be pictured as the energy contained by quiescent matter because of particle motion—the thermal energy—and because of particle interaction—the chemical energy. Attempts to separate these two parts thus far have yielded only qualitative discussions with no logical formulations. In the present paper, definitions of chemical available energy and thermal energy are justified and expressions for these new properties and their changes are rigorously developed. First, thermodynamic friction is defined to include not only the usual mechanical form, but also forms called here the chemical and thermal friction. Then, the concepts of chemical available energy, thermal available energy and thermal energy are defined, and the equations of change for these new properties are developed. It is proved quantitatively that mechanical and chemical friction are, respectively, the irreversible conversion of mechanical energy and chemical available energy into thermal energy of less availability, while thermal friction is the degradation of thermal energy through temperature gradients. The equations are applicable for chemically reacting or non-reacting fluid systems, with or without diffusion. The developments have been restricted to systems with conservative body forces, alike for all species, to avoid distracting attention from the main thesis: the mathematical and physical relationships between friction and available energy. 1 1 The definition of potential energy given in the first footnote of a previous paper [6] allows the development to be extended to systems with non-conservative, species-dependent body forces.