This method (GSE) is the same as the Grayson-Streed method with the exception that special liquid fugacity equations developed by Erbar of Oklahoma State University are used for N2, H2S and CO2. The original Grayson-Streed method uses the simple fluid model for these components.
See "Erbar Modification to Chao-Seader (CSE) and Grayson-Streed" under "Generalized Correlation Methods" in Chapter 2, Volume 1, of the PRO/II Reference Manual for more information.
Application Guidelines
The Erbar equations were developed from data for natural gas processing systems and do not give reliable results at temperatures above 400 degrees or pressures exceeding 1000 psia. This limits use of this method to processing conditions encountered in natural gas processes when significant quantities of N2, H2S, or CO2 are present. In particular, poor results have been observed for systems with CO2 at elevated temperatures.