The pseudocritical regions for supercritical water

Vapour pressure curves and stability lines can be extended beyond the critical points into the supercritical domain by so-called Widom lines, along which some thermodynamic property undergoes a rapid change and liquid-like behaviour turns to vapour-like one. Knowledge about such lines is therefore important for thermohydraulic calculations and design. There are several properties that can be chosen as defining property of a Widom line. In this short note we calculate and compare several kinds of Widom lines for water.

► Supercritical water behaves anomalously around the Widom lines.
► We calculated the location of the Widom lines for several thermodynamic functions.
► Simple quadratic fitting equations are given to describe these lines.