An Equation of State for Steam for Turbomachinery and Other Flow Calculations

Large-scale equations of state for steam used for generating tables are unsuitable for inclusion infinite difference flow calculation computer codes. Such codes, which are in common use in the turbomachinery industry, may require 10⁶ property evaluations before convergence is achieved. This paper describes a simple equation of state for superheated and two-phase property calculations for use in these circumstances. Computational efficiency is excellent and accuracy over the range of application is comparable to that of the large-scale equations. Further advantages are that complete thermodynamic consistency is maintained and the equation can be differentiated analytically for direct substitution into the gas dynamic equations where required. A truncated virial form is used to represent superheated properties and a new empirical correlation for the third virial coefficient of steam is presented.