## YXx X ni kIiJiJi 1x

Equation (15) covers region 2 of IAPWS-IF97 defined by the following range of temperature and pressure, see Fig. 1 273.15 K < T < 623.15 K 0 < p < ps ( T) Eq.(30) 623.15 K < T< 863.15 K 0 < p < p( T)Eq(5) 863.15 K < T < 1 073.15 K 0 < p < 100 MPa In addition to the properties in the stable single-phase vapor region, Eq. (15) also yields reasonable values in the metastable-vapor region for pressures above 10 MPa. Equation (15) is not valid in the metastable-vapor region...

## RTy0 yo yr nr

Where n p p and r T Twith R given by Eq. 1 . The equation for the ideal-gas part yo is identical with Eq. 16 except for the values of the two coefficients no and n 2, see Table 10. For the use of Eq. 16 as part of Eq. 18 the coefficients no and n 2 were slightly readjusted to meet the high consistency requirement between Eqs. 18 and 15 regarding the properties h and s along the saturated vapor line see below. The equation for the residual part yr reads where n pip and t T T with p 1 MPa and T...

## Basic Equation

The basic equation for this region is a fundamental equation for the specific Gibbs free energy g. This equation is expressed in dimensionless form, y g RT , and is separated into two parts, an ideal-gas part yo and a residual part yr, so that y k , t yo k , t yr k , t where k p p and r T Twith Rgiven by Eq. 1 . The equation for the ideal-gas part yo of the dimensionless Gibbs free energy reads where k p p and t T T with p 1 MPa and T 540 K. The coefficients nO and n2 were adjusted in such a...