Working Group: Thermophysical Properties of Water and Steam

The Thermophysical Properties of Water and Steam (TPWS) Working Group focuses on the characterization of the thermophysical properties of water and aqueous systems. Composed of experts with scientific and industrial backgrounds, the group conducts experimental and theoretical research to accurately determine the thermophysical properties of steam, water, ice, and aqueous mixtures and develops formulations for the thermophysical properties over a wide range of conditions, including temperature, pressure, and chemical composition, which are regarded as international standards in various scientific and industrial areas. The group's efforts contribute significantly to the understanding of the thermophysical properties of water, steam, and aqueous systems and provide guidelines on the application of formulations for the thermophysical properties in various areas such as energy conversion technology, ocean science, atmospheric science, and environmental studies to ensure accurate and reliable information for various scientific and industrial advances.

Current activities include the following:

Replacement of Standard Reference Equation of State for Water

In 1995, IAPWS adopted a standard formulation for the thermodynamic properties of ordinary water in its fluid phases, valid up to 1000 MPa and 1273 K. This equation of state has become known as IAPWS-95. While the accuracy of IAPWS-95 is excellent at conditions where reliable data existed for its development, new data (from experiments and also to some extent from molecular calculations) have revealed significant room for improvement in other regions. In addition, small flaws have been identified that could be avoided with modern equation-of-state technology. The Working Group is currently organizing existing data and identifying gaps, and will be constructing a replacement equation of state over the next few years.

Accurate Determination of Enhancement Factors for Water and Ice in Gases

Enhancement factors describe the solubility of ice and liquid water in a gaseous phase, and are essential for any application where knowledge of humidity is important. We will calculate enhancement factors in important gases such as helium, neon, argon, nitrogen, oxygen, air, hydrogen, hydrogen sulfide, carbon monoxide, carbon dioxide, and sulfur dioxide based on water-gas cross virial coefficients obtained from first principles. This approach yields more accurate enhancement factors than direct experimental measurements or a calculation using experimental data for the respective cross virial coefficients. The results of this project are to be issued in the form of an IAPWS Guideline.

For further information, please contact the Working Group officers:
Chair: Karsten Meier,, Helmut-Schmidt University
Vice-Chair: Jan Hrubý,, Institute of Thermomechanics, Acad. Sci. Czech Republic

This page updated December 7, 2023 >> Working Groups >> TPWS