Lee/Kesler Correlation: Accuracy & Complexity

[gfd43tg]

Hello,

I have been doing Lee/Kesler correlations ad nauseum to compare with calculated values for residual enthalpy and entropy with the Redlich/Kwong equation. My enthalpy values have varied as much as 400 J/mol with the correlation compared to the equation (enthalpy's in the 2500 J/mol range).

My question is why do I care about these Lee/Kesler correlations if they aren't even that accurate (assuming Redlich/Kwong is accurate) or vice versa if Lee/Kesler is accurate.

Also, why are these equations so horrendous for calculating the residual enthalpy and entropy with RLK? There is so much number crunching for it.

 

[Navin A S]

Thanks,Lee/Kesler correlations are used to approximate the properties of a substance that are not easily measured experimentally. They rely on a set of parameters (such as temperature and pressure) to approximate the behavior of the substance. Redlich/Kwong (RLK) equations are more accurate at predicting the thermal properties of a substance, but they require a more complex set of parameters to be calculated. The Lee/Kesler correlations are useful when you need a quick estimate of a property and don't have the time to calculate an exact value. However, they should not be used when an exact value is needed. In that case, the RLK equations should be used instead. In terms of why the equations are so complex for calculating the residual enthalpy and entropy with RLK, it is because the equations involve multiple independent variables and require a lot of calculations to determine the values.