Equation (4) can be rewritten in terms of the

compressibility factor, Z:

The specific terms and coefficients were determined by calculating a set of

compressibility factor values distributed in (p, T) space with the REFPROP (7) implementation of Eq.

3]/ mol Z

compressibility factor Greek Symbols [delta] fluid specific constant [epsilon] fluid specific constant [tau] reduced temperature function [omega] acentric factor [zeta] molar fraction Subscripts B Boyle c critical f liquid phase g vapour phase m mixture inv inversion nbp normal boiling point r reduced sat saturation

Introduction of

Compressibility Factor Z in Baldwin et al.

Dry air property equations were developed based on the ideal gas model and the

compressibility factor and virial contributions calculated by means of polynomial correlations as functions of pressure and temperature.

The physical part of the

compressibility factor [Z.

ext], the

compressibility factor, [gamma], and the slip coefficients on the tube wall.

Equations 3 and 4 constitute the second iterative loop of this model and solution results, in particular the

compressibility factor, are functions of temperature and pressure.

In fact, the

compressibility factor (Z) determines the amount of deviation from the behaviour of real flow rate, considering the behaviour of ideal flow rate.

g] is the molar gas constant, and Z is the

compressibility factor.

f] are the mass of the solute cylinder before and after the filling, M is the molar mass of the gas, R is the gas constant, Z is the

compressibility factor of the gas, and [m.

The

compressibility factor for natural gas is determined using the AGA 8 Thermodynamic Database [25].