# 11.2: Comparative Assessment of RK, SRK, and PR EOS

Over the years, these EOS have been tested, and some comparisons can be made. As an engineer, you have to be able to decide which EOS best fits your purposes.

## Redlich Kwong EOS:

• Generally good for gas phase properties.
• Poor for liquid phase properties.
• Better when used in conjunction with a correlation for liquid phase behavior.
• Satisfactory for gas phase fugacity calculation @ $$P_r < T_r/3$$.
• Satisfactory for enthalpy departure and entropy departure calculations.

## Soave Redlich Kwong & Peng Robinson EOS

• Serve similar functions as the Redlich Kwong EOS but require more parameters.
• PR obtains better liquid densities than SRK.
• Overall, PR does a better job (slightly) for gas and condensate systems than SRK. However, for polar systems, SRK always makes a better prediction, but in the petroleum engineering business we do not usually deal with those.