Formulation of the second axiom of thermodynamics using pressure motors

Abstract

In the normal teaching of thermodynamics as well as in the traditional textbooks, the second axiom is postulated in terms of thermal refrigerators and motors according to the Clausius and Kelvin-Planck's formulations, leaving open the possibility for generalizing the statement of the second axiom by means of motors and "refrigerators" associated to other intensive variables than temperature. In particular it is possible to employ pressure motors and vacuum pumps in the formulation of a corresponding second axiom, such that the maximum work is dependent on the pressure differences between two fixed "pressure reservoires". It is hoped that the teaching of this generalization of the second axiom leads the student to the understanding of two facts: first, that his perception of the fundamentals of thermodynamics is more profound, and second, that these fundamentals are not unalterable so that he could be responsible for its change. It might then be so that his learning of thermodynamics is more meaningful.