#
73rd Annual Gaseous Electronics Virtual Conference

## Volume 65, Number 10

##
Monday–Friday, October 5–9, 2020;
Time Zone: Central Daylight Time, USA.

### Session TR4: Reaction and Electron Kinetics

10:00 AM–11:45 AM,
Thursday, October 8, 2020

Chair: Vladimir Kolobov, CFD Reseach Corporation

### Abstract: TR4.00001 : What is the entropy extremum principle far away from local equilibrium?*

10:00 AM–10:15 AM
Live

Preview Abstract
Abstract

####
Author:

Elijah Thimsen

(Washington University in Saint Louis)

Predicting the direction of chemical reactions using thermodynamics requires
an entropy extremum principle. Under the governance of local equilibrium,
the system evolves towards a stationary equilibrium state, at which entropy
attains a constant maximum value. The equilibrium state is constrained by a
set of independent state variables, which are often taken to be the
temperature, pressure, and relative amounts of different chemical elements.
Nonequilibrium systems are classified into two regimes: linear and
nonlinear. In the linear regime, it has been argued that the entropy
generation rate, which is positive semidefinite according to the
2$^{\mathrm{nd}}$ law of thermodynamics, attains a \textit{minimum} value at stationary
states. For chemical reactions, a criterion must be fulfilled for operation
in the linear regime. The chemical affinity of a reaction must be much
smaller than the thermal energy: $A_{\mathrm{i}}$/\textit{RT}$_{\mathrm{M}}$ \textless
\textless 1, where $A_{\mathrm{i}}$ is the chemical affinity, $R$ is the ideal
gas constant, and $T_{\mathrm{M}}$ is the temperature of the gas. In
chemically reactive nonequilibrium plasmas, we have recently demonstrated
that stationary states are reached at which
$A_{\mathrm{i}}$/\textit{RT}$_{\mathrm{M}}$ \textgreater \textgreater 1, therefore the
system is governed by nonequilibrium, nonlinear thermodynamics. It is
currently unknown if an entropy extremum principle governs the nonlinear
regime. Discovery of that principle would have immense impact on a broad set
of disciplines, for example evolution of life on planet earth. In this
presentation, our published experimental data will be used to test a
recently proposed hypothesis that systems in the nonlinear regime evolve
towards constrained stationary states at which the entropy generation rate
is \textit{maximized}.

*NSF CBET 1847469