Thermodynamic property model for fluid-phase n-butane

A Helmholtz free energy equation of state for the fluid phase of n-butane ( R-600) has been developed on the basis of the ITS-90 temperature scale. Thi s model has been established on the basis of selected measurements of the p ressure-density temperature (P, p, T), isochoric heat capacity, speed of so und, and the saturation properties. The linear structural regression optimi zation and nonlinear fitting procedure were used to determine the functiona l form and the numerical parameters of the present equation of state. Based on a comparison with available experimental data, it is recognized that th e developed model represents most of the reliable experimental data accurat ely in the range of validity covering temperatures from 134.87 K (the tripl e-point temperature) to 589 K, at pressures up to 69 MPa, and at densities up to 745 kg (.) m(-3). The reasonable behaviors of the derived thermodynam ic propel tics have also been confirmed over the entire fluid phase of n-bu tane.