About

In power generation and HVAC engineering, the precise thermodynamic state of water is governed by the IAPWS-IF97 standard (International Association for the Properties of Water and Steam). Unlike simple look-up tables that rely on linear interpolation, this tool computes properties directly using the fundamental equations of state for Region 1 (Subcooled Liquid) and Region 2 (Superheated Vapor).

This utility is essential for sizing boilers, heat exchangers, and steam turbines. It determines the phase state automatically based on the saturation curve and returns high-precision values for Enthalpy (h), Entropy (s), and Specific Volume (v).

Formulas

Specific Enthalpy h is derived from the specific Gibbs free energy g via the relation:

h = g − T × ∂g∂Tp

Where g is approximated by a 34-term polynomial for liquid and a 43-term polynomial for vapor, scaled by the specific gas constant R (0.461526 kJ/kg·K).

Reference Data

Region	State	Independent Variables	Key Property Form
Region 1	Subcooled Liquid	p, T	g(p,T) (Gibbs Free Energy)
Region 2	Superheated Vapor	p, T	g(p,T) (Gibbs Free Energy)
Region 4	Saturation Line	p or T	p_sat(T) / T_sat(p)

Frequently Asked Questions

It is the industrial standard formulation adopted in 1997 for calculating the properties of water and steam. It replaces the older IFC-67 standard and is used in all modern power plant simulations for its computational speed and accuracy.

This simplified tool focuses on Region 1 (Liquid) and Region 2 (Vapor) up to 100 MPa and 800°C. It automatically detects if the input crosses the saturation line defined by the auxiliary equation for Psat.

Thermodynamic equations of state rely on absolute pressure. Gauge pressure (psig) varies with atmospheric conditions. 0 bar absolute is a perfect vacuum.