Thome-Enskog equation

The viscosity of a dense gas mixture of rigid, spherical molecules containing N components according to the Thome-Enskog equation can be written in the form (DiPippo etal. 1971 Vesovic Wakeham, 1989a,b)... 

In the case of the thermal conductivity, as has been discussed in Chapter 4 and Section 5.2, it is necessary to account for the transport of internal energy as well as translational energy. For that reason the Thome-Enskog equations in their original form for rigid, spherical molecules can be applied only to the translational component of the energy transport. Accordingly, before a method can be developed for the evaluation of... 

The Rainwater-Friend theory that has proved so successful in the representation of the initial-density dependence of the viscosity of pure gases has not been extended to mixtures. It is therefore necessary to make use of the Thome-Enskog equations... 

An alternative application of the Thome-Enskog equations is that en loyed by Veso-vic Wakeham (1989,1991). The procedure has been described in detail in Section 5.5, so that it is necessary here to describe only the sources of information employed. First the correlation of the viscosity of pure carbon dioxide has been taken from the work of Vesovic etal. (1990) and that of ethane from the workofHendl etal. (1994). For each temperature at which it was desired to evaluate the mixture viscosity these correlations were used in equation (5.53) to evaluate the pseudo-radial distribution functions g,- for each pure component, while equation (5.56) was used to determine a consistent value of the mean free-path shortening parameter a,-, for i-i interactions. Figure 15.3 contains a plot of the pseudo-radial distribution function determined in this way for the two pure gases at one temperature. 

The evaluation of the excess contribution to the thermal conductivity of carbon dioxide-ethane mixtures has been performed by a route parallel to that employed for the viscosity. Again, that route has been described in detail in Section 5.5.1.2 so that here it is merely recorded that for pure carbon dioxide and pure ethane the thermal conductivity has been taken from the work of Vesovic et al. (1990, 1994). All other quantities required for the calculation are the same as those employed for the zero-density thermal conductivity. In this context it should be noted that the Thome-Enskog equations employed for these calculations have, as their zero-density limit, the Hirschfelder-Eucken result in the form of equation (15.5). Figure 15.3 contains the pseudo-radial distribution functions for carbon dioxide and ethane determined... 

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