26 - The pivotal functions

Abstract

The entropy production function and the energy retention function are referred to as the pivotal functions of the theory of coupled linear steady-state thermodynamics. This chapter extends their definition and meaning in some generality to the vector and tensor theories and elaborates some of their salient features. The entropy production function is the sum of the products of the thermodynamic fluxes and their conjugate driving forces. If tensorial cross-effects are negligible, the Curie symmetry principle allows one to extend earlier definition of the entropy production function, as one of the two pivotal functions of steady-state thermodynamics to include scalar, vector, and tensor quantities alike. It explains neither the entropy production function nor the energy retention function is determined uniquely. It suffices that the products of whatever are chosen as the generalized fluxes and driving forces have the dimensions of entropy per unit time per unit volume and energy per unit time per unit volume, respectively.