Abstract

We propose the concept of global temperature for spatially non-uniform heat conduction systems. With this novel quantity, we present an extended framework of thermodynamics for the whole system such that the fundamental relation of thermodynamics holds, which we call “global thermodynamics” for heat conduction systems. Associated with this global thermodynamics, we formulate a variational principle for determining thermodynamic properties of the liquid-gas phase coexistence in heat conduction, which corresponds to the natural extension of the Maxwell construction for equilibrium systems. We quantitatively predict that the temperature of the liquid–gas interface deviates from the equilibrium transition temperature. This result indicates that a super-cooled gas stably appears near the interface.

Highlights

  • The behavior of liquids and gases close to equilibrium have been extensively studied for a long time

  • A = d3r a(T (r), p(r))ρ(r) = a(T, p)N + O(ε2). This indicates that all global thermodynamic quantities are equivalent to those in equilibrium by adopting the global temperature Tin (10.1), and that global thermodynamics for heat conduction systems are generally mapped to equilibrium thermodynamics, regardless of the shape of the container

  • We have developed a thermodynamic framework for heat conduction states, which we call global thermodynamics

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Summary

Introduction

The behavior of liquids and gases close to equilibrium have been extensively studied for a long time. In this paper, we construct a new universal theory for thermodynamic properties in the linear response regime. A new concept, global temperature, is found, with which a novel framework of global thermodynamics is constructed to describe the whole of non-uniform non-equilibrium systems with local equilibrium thermodynamics. This outcome provides a fresh viewpoint for the description of systems out of equilibrium. In the remaining part of this introduction, we first present a brief summary of development in non-equilibrium statistical mechanics, confirming that the phenomenon described above has never been discussed by established theories. At the end of the introduction, we summarize the achievements of this paper

Non-equilibrium Statistical Mechanics
Extended Frameworks of Thermodynamics
Summary of Results
Equilibrium Thermodynamics
Setup of Heat Conduction Systems
Local Equilibrium Thermodynamics
Global Conditions for Steady States
Global Thermodynamic Quantities
Global Thermodynamics for Single-Phase Systems in the Linear Response Regime
Various Global Thermodynamic Functions
Clausius Equality
Correspondence of Global Thermodynamic Quantities to Equilibrium Quantities
Liquid–Gas Coexistence in Heat Conduction
Thermodynamics Under Equilibrium Conditions
Heat Conduction States
Global Quantities as a Function of X
Problem
Variational Principle for Determining the Liquid–Gas Interface Position
Equilibrium Systems
Extension to Heat Conduction Systems
Remarks
Steady State Determined from the Variational Principle
Temperature Relation
Properties of the Steady States with a Liquid–Gas Interface
Super-Cooled Gas in the Liquid–Gas Coexistence
Examples
Global Thermodynamics for Systems with a Liquid–Gas Interface
Preliminaries
Formal Derivation of Fundamental Relation
Explicit Forms of Seq and Veq
Heat Capacity and Compressibility
Fundamental Relation
Free Energy for the Coexistence Phase
Other Assumptions Leading to the Results of the Variational Principle
Variational Principle for Constant Volume Systems
Heat Conduction Systems
Thermodynamic Relation
Singularity Relation
Scaling Relation
10 Generalization for Single Phase Systems
10.1 Global Thermodynamic Quantities in an Arbitrarily Shaped Container
10.2 Equivalence of Non-equilibrium Global Quantities with Equilibrium Quantities
10.3 Fundamental Relation Beyond the Linear Response Regime
10.3.3 Factor Determined by the Geometry of Containers
11 Concluding Remarks

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