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The International Association for the Properties of Water and Steam (IAPWS) has not only developed an international standard for the thermodynamic properties of water and steam (see Introduction to IAPWS-IF97 and Equations of IAPWS-IF97) but also equations for transport properties and other properties [1-5]. We have summarized the equations for calculating the transport properties dynamic viscosity and thermal conductivity as well as the surface tension of the interface between the liquid and the vapor phase of water in an Adobe pdf-file. IAPWS also gives equations for the static dielectric constant and the refractive index of water which are of less interest in chemical engineering applications. If required these equations can be found in the references [1, 2].

The equations for dynamic viscosity and thermal conductivity are given as a function of temperature and density. The use of density as an independent variable makes it possible to calculate properties of the liquid and vapor phase using one single equation. In most cases, however, temperature and pressure are the independent variables and the density must be determined first from the IAPWS-IF97 equations.

Viscosity can be calculated for temperatures from 0 °C to 900 °C and for pressures up to at least 3000 bar depending on the temperature. The equation for thermal conductivity can be applied for temperatures from 0 °C to 800 °C and pressures up to at least 1000 bar. Surface tension can be calculated over the whole range where a liquid-vapor interface exists, i.e. from the triple point to the critical point of water. Accuracy of the equations is more than sufficient for engineering applications. Details can be found in the references [3-5].

References

1. William T. Parry et al., ASME International Steam Tables for Industrial Use, American Society of Mechanical Engineers 2000.
2. W. Wagner, A. Kruse, Properties of Water and Steam, Springer-Verlag, Berlin 1998.
3. IAPWS Release on the Viscosity of Ordinary Water Substance, IAPWS Secretariat 1997.
4. IAPWS Release on the Thermal Conductivity of Ordinary Water Substance, IAPWS Secretariat 1998.
5. IAPWS Release: "Surface Tension of Ordinary Water Substance", IAPWS Secretariat 1994.

IAPWS Releases are available from the Executive Secretary of IAPWS.

Part I: Introduction to IAPWS-IF97
Part II: Equations of IAPWS-IF97

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