Figures 2, 3, 4, 5 show error estimations for specific volume, isobaric heat capacity, saturation pressure and sound velocity calculated on equations of Formulation IF–97 . That are the tolerances for the values considered and have no static sense. The message «tolerace cannnot be determined» is connected with the region where extrapolated values from [1] are used as initial data for the equation.
Error for dynamic viscosity for liquid: at pressure up to 100 MPa and temperature up to 250 °C is 1%, up to 300 °C – 2%, at 350 °C and above – 3%. For steam at pressure up to 50 MPa and temperature up to 475 °C that amount to 2%, and at higher pressure and temperature – 3%.
Error for thermal conductivity for liquid: at temperature range 25 – 200 °C and pressure up to 5 MPa is 1.5%, and at higher pressure and temperature up to 300 °C – 2%. For steam at temperature up to 550 °C and pressure up to 0.1 MPa is 1.5%, and at pressure up to 40 MPa – 3%. The equation for thermal conductivity gives a finite value in critical point, while it must be infinite according to the theory. Correspondingly, the error for thermal conductivity cannot be estimated close to critical point.
Fig. 2. Relative error for specific volume
For critical region (hatched triangle), bordered by isohoric lines 0,0019 and 0,0069 m3/kg and isobar 30 MPa. Relative error for pressure is marked.
Fig. 3. Relative error for specific isobaric heat capacity
Borders of critical region (hatched triangle) – see. fig. 2
Fig. 4. Relative error for sound velocity
Borders of critical region (hatched triangle) – see. fig. 2
Fig. 5. Relative error for saturation pressure