ABSTRACT
This chapter presents equilibrium thermodynamics. Thermodynamics places strong constraints on the interactions of the various processes, which further clarifies experimental predictions. Thermodynamics in general deals with the average properties of a system and describes transformations between work and energy in various forms. The limitation of equilibrium thermodynamics is that it describes static processes. Non-linear classical field theory is also commonly referred to as thermostatics, since it is the limit that non-equilibrium thermodynamics reduces to in the absence of motion. M. A. Biot's work on poroelasticity was founded on a 'megascopic thermodynamics' in which the relations were equivalent in form to single-component equilibrium thermostatics. Megascopic systems such as porous media contain additional dynamic variables not present in macroscopic systems such as elastic solids and Newtonian fluids. The discussion of thermodynamics was expanded from that of a chemically homogeneous system based on mass fractions to include the new dynamic variable porosity.
