Supplementary Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the Industrial Formulation IAPWS-IF97 for Water and Steam

Published

July 11, 2006

Author(s)

H J. Kretzschmar, J Cooper, A Dittmann, J Trubenbach, Th Willkommen, Daniel G. Friend, J S. Gallagher, Radim Mares, Kiyoshi Miyagawa, Wolfgang Wagner, K Knobloch, I. Stocker

Abstract

In 2001, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for pressure as a function of enthalpy and entropy p(h, s) as supplement to the IAPWS Industrial Formulation 1997 for the Termodynamic Properties of Water and Steam (IAPWS-IF97). The p(h,s) equations are valid in the liquid region 1 and the region 2. With pressure p, temperature T(h, s), can be calculated using the IAPWS-IF97 backward equations T(h,s). When using the p(h,s) equations, the two-dimentional iterations of the IAPWS-IF97 basic equations can be avoided. The numerical consistency of pressure and temperature obtained in this way is sufficient for most heat cycle calculations. This paper summarizes the need and the requirements for the p(h,s) equations and gives complete numerical information about the equations. Moreover, the quality of the p(h,s) equations and the calculation of the backward function T(h,s) is presented regarding three aspects: numerical consistency with the IAPWS-IF97 basic equations consistency along subregion boundaries, and computation speed important for industrial use.

Citation

Journal of Engineering for Gas Turbines and Power-Transactions of the ASME

Volume

128

Pub Type

Journals

Download Paper

Local Download

Keywords

enthalpy, IAPWS, industrial formulation, water properties

Citation

Kretzschmar, H. , Cooper, J. , Dittmann, A. , Trubenbach, J. , Willkommen, T. , Friend, D. , Gallagher, J. , Mares, R. , Miyagawa, K. , Wagner, W. , Knobloch, K. and Stocker, I. (2006), Supplementary Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the Industrial Formulation IAPWS-IF97 for Water and Steam, Journal of Engineering for Gas Turbines and Power-Transactions of the ASME, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831910 (Accessed October 27, 2025)