An action principle of classical irreversible thermodynamics - Irreversible thermodynamic cycles and embodied bits of information

Abstract

Despite its simplicity, it seems to my best of knowledge that the possibly simplest approach towards deriving equations governing irreversible thermodynamics from gas-kinetic considerations within the framework of classical mechanics has never been pursued. In this paper we address this omission and derive the equations describing the irreversible thermodynamics of a gas in a piston and associated thermodynamic cycles performed in finite time. What we find is a thermodynamic action principle: The irreversible work we require for performing a thermodynamic cycle in finite time times the time we require to run through the cycle, a isothermal compression/decompression cycle for instance, will always be larger or equal to a lower bound given by a system specific constant with the dimension of an action. This process specific action constants can take values of the order of Plank's constant for microscopic processes, such as displacing a Hydrogen atom by one atom diameter. For macroscopic processes (e.g. a bicycle pump) also the action constant takes macroscopically observable values. We discuss the finite time Carnot cycle, and estimate the lower bound for irreversible work required when rewriting physically embodied bits of information and compare the resulting values with Landauer's bond, the irreversible amount of energy that needs to be dissipated for re-writing a bit.