Correcting for High Pressure

Jossi et al. (1962) presented a generalized correlation for the viscosity of high density fluids as a function of the reduced density via a corresponding states method. This method was discussed earlier. Among the gases that Jossi et al. (1962) used to build their correlation were carbon dioxide, methane, ethane, and propane. This gives us some confidence that this approach should be satisfactory for our acid gas mixtures. 

Although the Jossi et al. (1962) correlation will not be used in this study, it will be used as a guide for building a new correlation. Therefore, we seek a function of the form  

Pure C02 will be used as the reference fluid and take the viscosity data from the tables of Vesovic et al. (1990). The densities will be 

The first attempt at correlating the viscosity used a polynomial in density. The correlation that resulted was  

By most statistical measures, this was an excellent fit of the data (for example r2 = 0.9929). However, this correlation was deemed unsatisfactory for two reasons. First, the equation had a curvature that was not indicated by the data set. This is a common problem when one attempts to fit a set of data with a polynomial. Second, it resulted in significant errors in the low-density region. Seeming small statistical errors translate into large errors in the estimate viscosity. 

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For predicting the vapour viscosity at Tr > 0.6, low pressure values, are calculated from a low pressure equation and then corrected for high pressure by the method of Dean and Stiel [16] with the following equations ... 

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