In modeling steam power cycles, thermodynamic properties as functions of the variables enthalpy and entropy are required in the liquid and the vapor regions. It is difficult to perform these calculations with IAPWS-IF97, because they require two-dimensional iterations calculated from the IAPWS-IF97 fundamental equations. While these calculations are not frequently required, the relatively large computing time required for two-dimensional iteration can be significant in process modeling. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for pressure as a function of enthalpy and entropy as a supplement to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97) in 2001. These equations are valid in the liquid region 1 and the vapor region 2. With pressure , temperature can be calculated from the IAPWS-IF97 backward equations . By using the equations, the two dimensional 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 equations and gives complete numerical information about the equations. Moreover, the achieved quality of the equations and their use in the calculation of the backward function is presented. The three aspects, numerical consistency with the IAPWS-IF97 basic equations, consistency along subregion boundaries, and computational speed important for industrial use are discussed.
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July 2006
Technical Papers
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
H.-J. Kretzschmar,
H.-J. Kretzschmar
Department of Technical Thermodynamics,
e-mail: hj.kretzschmar@hs-zigr.de
University of Applied Sciences of Zittau and Gorlitz
, P. O. Box 1455, D-02754 Zittau, Germany
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J. R. Cooper,
J. R. Cooper
Department of Engineering,
Queen Mary University of London
, London, UK
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A. Dittmann,
A. Dittmann
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, Germany
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D. G. Friend,
D. G. Friend
Physical and Chemical Properties Division,
National Institute of Standards and Technology
, Boulder, CO
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J. S. Gallagher,
J. S. Gallagher
Physical and Chemical Properties Division,
National Institute of Standards and Technology
, Gaithersburg, MD
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K. Knobloch,
K. Knobloch
Department of Technical Thermodynamics,
University of Applied Sciences of Zittau and Gorlitz
, P.O. Box 1455, D-02754 Zittau, Germany
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R. Mareš,
R. Mareš
Department of Thermodynamics,
University of West Bohemia
, Plzeň, Czech Republic
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I. Stöcker,
I. Stöcker
Department of Technical Thermodynamics,
University of Applied Sciences of Zittau and Gorlitz
, P.O. Box 1455, D-02754 Zittau, Germany
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J. Trübenbach,
J. Trübenbach
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, Germany
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W. Wagner,
W. Wagner
Lehrstuhl für Thermodynamik,
Ruhr-Universität Bochum
, Bochum, Germany
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Th. Willkommen
Th. Willkommen
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, Germany
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H.-J. Kretzschmar
Department of Technical Thermodynamics,
University of Applied Sciences of Zittau and Gorlitz
, P. O. Box 1455, D-02754 Zittau, Germanye-mail: hj.kretzschmar@hs-zigr.de
J. R. Cooper
Department of Engineering,
Queen Mary University of London
, London, UK
A. Dittmann
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, Germany
D. G. Friend
Physical and Chemical Properties Division,
National Institute of Standards and Technology
, Boulder, CO
J. S. Gallagher
Physical and Chemical Properties Division,
National Institute of Standards and Technology
, Gaithersburg, MD
K. Knobloch
Department of Technical Thermodynamics,
University of Applied Sciences of Zittau and Gorlitz
, P.O. Box 1455, D-02754 Zittau, Germany
R. Mareš
Department of Thermodynamics,
University of West Bohemia
, Plzeň, Czech Republic
K. Miyagawa
Tokyo, Japan
I. Stöcker
Department of Technical Thermodynamics,
University of Applied Sciences of Zittau and Gorlitz
, P.O. Box 1455, D-02754 Zittau, Germany
J. Trübenbach
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, Germany
W. Wagner
Lehrstuhl für Thermodynamik,
Ruhr-Universität Bochum
, Bochum, Germany
Th. Willkommen
Department of Technical Thermodynamics,
Technical University of Dresden
, Dresden, GermanyJ. Eng. Gas Turbines Power. Jul 2006, 128(3): 702-713 (12 pages)
Published Online: June 22, 2004
Article history
Received:
October 20, 2003
Revised:
June 22, 2004
Citation
Kretzschmar, H., Cooper, J. R., Dittmann, A., Friend, D. G., Gallagher, J. S., Knobloch, K., Mareš, R., Miyagawa, K., Stöcker, I., Trübenbach, J., Wagner, W., and Willkommen, T. (June 22, 2004). "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." ASME. J. Eng. Gas Turbines Power. July 2006; 128(3): 702–713. https://doi.org/10.1115/1.1915392
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