Creation of entropy

In contrast to thermodynamic properties, transport properties are classified as irreversible processes because they are always associated with the creation of entropy. The most classical example concerns thermal conductance. As a consequence of the second principle of thermodynamics, heat spontaneously moves from higher to lower temperatures. Thus the transfer of AH from temperature to T2 creates a positive amount of entropy ... 

THOMSON PRINCIPLE. The hypothesis that, if thermodynamically reversible and irreversible processes take place simultaneously in a system, the laws of thermodynamics may be applied to the reversible process while ignoring for this purpose the creation of entropy due to die irreversible process. Applied originally by Thomson to the case of... 

It can be readily shown (29) that the internal creation of entropy, dSh is given by... 

In the irreversible process the total entropy change is always positive i.e., there is a net creation of entropy. Degradation of work due to its irreversible nature accounts for this creation of entropy. 

In an advancing irreversible process such as a mechanical movement of a body, dissipation of energy for instance from a mechanical form to a thermal form (frictional heat) takes place. The second law of thermodynamics defines the energy dissipation due to irreversible processes in terms of the creation of entropy Slrr or the creation of uncompensated heat Qirr. 

This equation 3.10 defines the creation of uncompensated heat Qlrr and the creation of entropy Sirr ... 

As an irreversible process advances in a closed system, the creation of entropy inevitably occurs dissipating a part of the energy of the system in the form of uncompensated heat. The irreversible energy dissipation can be observed, for instance, with the generation of frictional heat in mechanical processes and with the rate-dependent heat generation in chemical reactions different from the reversible heat of reaction. In general, the creation of entropy is always caused by the presence of resistance against the advancement in irreversible processes... 

According to irreversible thermodynamics [Ref. 2.], the rate of the creation of uncompensated heat, which equals the rate of the creation of entropy times the absolute temperature, is equivalent to the driving force A times the rate v = d /dt of the irreversible reaction as shown in Eq. 3.14 (vid. Eq. 3.39) ... 

No creation of entropy and uncompensated heat occurs in the reversible heat engine and pomp, and hence Eq. 3.45 gives the maximum efficiency theoretically attainable for heat engines and heat pumps. This equation also shows that thermal energy (heat) can not be... 

The affinity of irreversible processes is a thermodynamic function of state related to the creation of entropy and uncompensated heat during the processes. The second law of thermodynamics indicates that all irreversible processes advance in the direction of creating entropy and decreasing affinity. This chapter examines the property affinity in chemical reactions and the relation between the affinity and various other thermodynamic quantities. 

In a reversible process, the maximum external work is dw = —dG. Irreversible change in the system decreases the maximum external work of the system by TdiS, the energy associated with creation of entropy in the system. For a finite state change, the available external work is... 

This distinction between heat which is exchanged with the outside world, and that which is produced within the system enables us to give a physical significance to equation (3.5). The entropy of a system can vary for two reasons and for two reasons only either by the transport of entropy to or from the surroundings through the boundary surface of the system, or by the creation of entropy inside the system. 

The inequality (3.4) states that the creation of entropy is always positive, that is to say irreversible processes can only create entropy, they cannot destroy it. We note that for an isolated system... 

The idea of the creation of entropy will play a fundamental role throughout this work. Instead of limiting ourselves to qualitative statements as to the sign of the entropy production however, the method we shall employ is based upon its quantitative evaluation. This enables us to discard the limitation imposed by the classical method to a discussion of reversible processes, and permits the development of the thermodynamics of irreversible phenomena, based on a study of real transformations. 

The choice of the thermodynamic potential to indicate the presence of irreversible changes, and the possibility of employing such a potential, depends upon the type of change considered. On the other hand the definition of irreversibility in terms of the creation of entropy—zero in the absence of irreversible processes, and positive in their presence— is completely general. 

The Creation of Entropy in Physico-chemical Changes in Uniform Systems. 

On the other hand the method adopted in this work, based upon the creation of entropy, is independent of all hypotheses as to the type of irreversible process under consideration. 

In the last chapter we introduced a precise definition of the affinity of a chemical reaction based upon the creation of entropy. The most important property of the affinity is expressed by the fundamental inequality... 

In the presence of a nonuniformity in concentration a diffusive flux occurs, resulting in the creation of entropy. The rate of irreversible entropy production is, in general, a homogeneous quadratic function of the gradients of... 

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