Statistical Mechanics Application to Real Fluids

Statistical Mechanics Application to Real Fluids b.Internal Energy... 

After the seminal work of Guggenheim on the quasichemical approximation of the lattice statistical-mechanical theory[l], various practical thermodynamic models such as excess Gibbs energies[2-3] and equations of state[4-5] were proposed. However, the quasichemical approximation of the Guggenheim combinatory yields exact solution only for pure fluid systems. Therefore one has to resort to numerical procedures to find the solution that is analytically applicable to real mixtures. Thus, in this study we present a new unified group contribution equation of state[GC-EOS] which is applicable for both pure or mixed state fluids with emphasis on the high pressure systems[6,7]. 

In practice, however, due to the limitations in the applicability of Statistical Mechanics to real fluids, that will be considered in Chapters 16 and 17, evaluation of thermodynamic properties is carried out with the approach discussed next. 

Application of statistical mechanics to real fluids becomes difficult because of the complications that arise from the presence of intermolecular forces. Through simplifications and approximations, however, more and more understanding of the properties of such fluids is achieved through statistical mechanics, as outlined in the next Chapter. 

Through approximations and the use of molecular simulation, however, application of statistical mechanics to real fluids has provided enhanced understanding of their behavior and improved description of it through equations of state. Furthermore, the molecular approach of statistical mechanics, as compared to the macroscopic one of traditional thermodynamics, combined with molecular simulation renders it a very useful tool in new applications biochemical processes prediction of matter behavior at and near surfaces, for example in porous materials or thin films ceramic materials polymers etc. 

Our objective in this Chapter is to review very briefly some of the approximations involved in applying statistical mechanics to real fluids. Apparently this is a complex subject with continuously growing applications and its detailed discussion is beyond the scope of this book. It is... 

The motivation for establishing accurate values of the various transport properties has been discussed in previous chapters. The current stams of fundamental kinetic and statistical mechanical theory, computer simulation and experimental technique and data acquisition impose severe limits on the accuracies achievable in any description of a transport property surface for a real fluid. For instance, it will not be possible to determine viscosities to one part in 10 for the near future. Thus, the accuracies associated with primary standards for transport properties fall an order of magnitude below those associated with primary measurement standards for equilibrium thermodynamic properties. Fortunately, the technological applications of transport property information do not require extreme accuracies. 

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