Calculates saturated water/steam properties based on the steam tables, IF97 formulation (IAPWS-IF97).
Two calculation methods are available: from $T$ and $x$ or from $P$ and $x$, where $x$ is the mass fraction, or vapor quality. For two-phase mixtures, properties are interpolated by quality:
$$ h = x \cdot h_{vap} + (1 - x) \cdot h_{liq} \ \quad s = x \cdot s_{vap} + (1 - x) \cdot s_{liq} \ \quad c_p = x \cdot c_{p,vap} + (1 - x) \cdot c_{p,liq} $$