Nonequilibrium calorimetry

TL;DR

This paper introduces a nonequilibrium heat capacity concept for driven systems in contact with a thermal bath, linking heat dissipation to temperature changes and proposing a practical measurement method via heat flux response.

Contribution

It generalizes equilibrium thermodynamics to nonequilibrium steady states and offers a new way to experimentally determine heat capacity from heat flux responses.

Findings

Defines nonequilibrium heat capacity as excess dissipated heat.

Proposes a method to measure heat capacity through heat flux response.

Connects heat dissipation with temperature variations in driven systems.

Abstract

We consider stationary driven systems in contact with a thermal equilibrium bath. There is a constant (Joule) heat dissipated from the steady system to the environment as long as all parameters are unchanged. As a natural generalization from equilibrium thermodynamics, the nonequilibrium heat capacity measures the excess in that dissipated heat when the temperature of the thermal bath is changed. To improve experimental accessibility we show how the heat capacity can also be obtained from the response of the instantaneous heat flux to small periodic temperature variations.