BASIC PRINCIPLES OF NON-EQUILIBRIUM THERMODYNAMICS

Systems in equilibrium are simple so far as analysis is concerned. The moment we move away from equilibrium or far away from equilibrium, we immediately enter the region of complexity. For analysis of such situations, new procedures have to be involved. Non-equilibrium thermodynamics is amongst such powerful tools for which a number of monographs are available [1-11]. We shall give a brief and concise account of the subject in this chapter with special reference to steady states close to equilibrium. 

Living systems and social systems are quite complex open systems. They consist of many sub-systems between which interaction can take place. In the world of today, we have continents and nation states between which continuous interaction takes place. Even such nations can have various sub-units as we have in the United States, which can act for separate sub-systems for a limited purpose. The interaction between such sub-systems may be quite complex depending on the geographical location, ethnic and political considerations. 

Non-equilibrium thermodynamics (NET) as it developed turned out to be quite useful in basic understanding of non-equilibrium steady states close to equilibrium and also in the region far from equilibrium. The theoretical and experimental studies can serve as a model for studies of similar type of real systems including biological, social and economic systems. 

In this chapter, the main objective is to present the basic principles of NET in a concise form. Applications to specific systems and phenomena along with correlation of theory and experiment have been discussed in subsequent chapters. 

Open systems are typical non-equilibrium systems, which display a variety of exotic phenomena. Typical examples are Continuous Stirred Tank Reactor (CSTR) (Fig. 2.1) and the living state. 

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Chapter 2. Basic Principles of Non-Equilibrium Thermodynamics 2.4.2. For continuous systems... 

The book is divided into four parts. Part One, which consists of six chapters, deals with basic principles and concepts of non-equilibrium thermodynamics along with discussion of experimental studies related to test and limitation of formalism. Chapter 2 deals with theoretical foundations involving theoretical estimation of entropy production for open system, identification of fluxes and forces and development of steady-state relations using Onsager reciprocity relation. Steady state in the linear range is characterized by minimum entropy production. Under these circumstances, fluctuations regress exactly as in thermodynamics equilibrium. 

The main objective of performing kinetic theory analyzes is to explain physical phenomena that are measurable at the macroscopic level in a gas at- or near equilibrium in terms of the properties of the individual molecules and the intermolecular forces. For instance, one of the original aims of kinetic theory was to explain the experimental form of the ideal gas law from basic principles [65]. The kinetic theory of transport processes determines the transport coefficients (i.e., conductivity, diffusivity, and viscosity) and the mathematical form of the heat, mass and momentum fluxes. Nowadays the kinetic theory of gases originating in statistical mechanics is thus strongly linked with irreversible- or non-equilibrium thermodynamics which is a modern held in thermodynamics describing transport processes in systems that are not in global equilibrium. 

A most often observed fact of colloid and surface chemistry is that work must be done in order to create a new surface. This law is a basic principle not only valid for liquid interfaces, as shown in Chapter 1, but also for solid bodies work is necessary for grinding and crushing for example. Surface thermodynamics starts from the ftmdamental principles of the general thermodynamics and includes equilibrium and non-equilibrium states. 

In order to simplify these equafimis, the basic principle of microscopic reversibility introduced by Onsager in the 1930s can be evoked [70]. According to this principle, used to derive the reciprocal relations in non-equilibrium thermodynamics, there is a local reversibility of all (sub-)processes even though the system is out of equilibrium. Hence, applying this principle, which is strictly speaking only likely to be valid close to equilibrium, we can write ... 

The data reduction of vapor-pressure osmometry (VPO) follows to some extent the same relations as outlined above. However, from its basic principles, it is not an equilibrium method, since one measures the (very) small difference between the boiling point temperatures of the pure solvent drop and the polymer solution drop in a dynamic regime. This temperature difference is the starting point for determining solvent activities. There is an analogy to the boiling point elevation in thermodynamic equilibrium. Therefore, in the steady state period of the experiment, the following relation can be applied if one assumes that the steady state is sufficiently near the vapor-liquid equilibrium and linear non-equilibrium thermodynamics is valid ... 

The basic thermodynamic, kinetic, and structural principles which govern the crystallization behavior of polymers have been developed so far. These principles can now be applied to give an understanding of the properties of semicrystalline polymers. There is a continuing interest in understanding the properties of crystalline polymers in terms of structure. Because of the non-equilibrium character of the... 

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