Four-Parameter Generalized Compressibility Charts for Nonpolar Fluids

Abstract

A series of five generalized compressibility charts for nonpolar and slightly polar substances in the gaseous and liquid states and in the two-phase region is presented. The charts are plots of the compressibility factor Z versus the reduced pressure Pr with the reduced temperature Tr as a parameter. Each chart is for a group of substances with similar values of the critical compressibility factor Zc and the slope of the reduced vapor-pressure curve at the critical point, αc . The use of four independent parameters (Pr , Tr , Zc , and αc ) results in an increase in accuracy over existing methods of presenting compressibility charts.