Chemical potential dissipative term

Returning to Equation (15), it is noted that = 0 the steady state because although energy is being dissipated, this is supplied exactly by transfer of water at high chemical potential in bulk to low chemical potential at the membrane. For the unsteady state, the second term in brackets is not zero and this is no longer true. Equation (15) must then be evaluated from the solution of a partial differential equation which describes the particular unsteady state in question. 

Because wrev is the maximum available work of any type, we can say from (5.53) that AG is the maximum available non-PV work. Here, available (or free ) refers to the idealized reversible limit in which no useful work is dissipated. Practically speaking, the major non-PV work of interest to chemists is the chemical energy (as manifested, for example, in electrochemical or osmotic phenomena), associated with the chemical potential terms that will be introduced in Chapter 6. 

The expression for shows, that the entropy flux for open systems consists of two parts the thermal flux associated with the heat transfer, and the flux due to diffusion. The second expression consists of four terms associated with, respectively, the heat transfer, diffusion, viscosity, and chemical reactions. The expression for the dissipative function a has quadratic form. It represents the sum of products of two factors a flux (specifically, the heat flux /, diffusion flux momentum flux n, and the rate of a chemical reaction and a thermodynamic force, proportional to gradient of some intensive variable of state (temperature, chemical potential, or velocity). The second factor can also include external force F]t and chemical affinity Aj. 

The second term corresponds to entropy production that is, its change is not due to a redistribution of the parts of the system but due to different dissipative processes of chaotization (temperature equalizing, chemical potential equalizing, and chemical reaction processes). Entropy generation (urihke its fiiU change) is always positive and approaches zero only at equilibrium. Usually, entropy generation is determined per unit volume and unit time ... 

The disposition of the radioactive waste resulting from spent nuclear-fuel reprocessing is one of the major problems of nuclear technology. Many of these wastes are high-level (HLW) and present a potential environmental hazard. Because of the expense associated with long-term storage, it is desirable to minimize the volume of radioactive waste and store it as material with maximal chemical stability to avoid the dissipation of radionuclides in the environment. 

If there are no dissipative effects, that is, friction, viscosity, inelasticity, electrical resistance, and so on, during a quasi-static process, the process is termed reversible. Only an infinitesimal change is required to reverse the process, a concept that leads to the name reversible. Most industrial processes exhibit heat transfer over finite temperature differenees, mixing of dissimilar substances, sudden changes in phase, mass transport under finite concentration differences, free expansion, pipe friction, and other mechanical, chemical, and thermal nonidealities, and consequently are deemed irreversible. An irreversible process always involves a degradation of the potential of the process to do work, that is, will not produce the maximum amount of work that would be possible via a reversible process (if such a process could occur). 

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