Sage Journals: Discover world-class research

Abstract

The results of the International Wet Steam Modelling Project presented at the Wet Steam Conference in Prague in 2016 again gave rise to a discussion about the suitability of the flow solver ANSYS CFX for the prediction of spontaneous condensation. In this article, the main reason for the discrepancy between results obtained with CFX and measurement data is identified. It could be found that in CFX the temperature of already existing droplets is used for evaluating the fluid properties involved in the nucleation process. This is not in agreement with the isothermal classical nucleation theory, which is based on the assumption that clusters of critical radius are formed at vapour temperature. The most dominant parameter affected by this is the surface tension, the evaluation of which can be altered easily by the user. The influence of the correction is illustrated by means of standard Laval nozzle test cases, and a significant improvement of the results compared to measurement data can be observed.

Keywords

Wet steam spontaneous condensation Laval nozzle ANSYS CFX

Get full access to this article

View all access options for this article.

References

Starzmann J, Hughes FR, White AJ, et al. Results of the international wet steam modelling project. In: Bartoš O and Kolovratník M (eds)Wet Steam Conference, Prague, Czech Republic, 12–14 September 2016.

Starzmann J. Numerische Untersuchung der Zweiphasenströmung und Analyse von Nässeverlusten in Niederdruckdampfturbinen. Dissertation, University of Stuttgart, Germany, 2014.

Grübel

Starzmann

Schatz

et al.

Two-phase flow modeling and measurements in low-pressure turbines – part 1: numerical validation of wet steam models and turbine modeling. Trans ASME, J Eng Gas Turb Power 2015; 137: 042602–1–11.

Becker

Döring

. Kinetische Behandlung der Keimbildung in übersättigten Dämpfen. Annalen der Physik 1935; 416: 719–752.

Bakhtar

Young

White

et al.

Classical nucleation theory and its application to condensing steam flow calculations. Proc IMechE, Part C: J Mechanical Engineering Science 2005; 219: 1315–1333.

Kantrowitz

. Nucleation in very rapid vapor expansions. J Chem Phys 1951; 19: 1097–1100.

Young

. The spontaneous condensation of steam in supersonic nozzles. Physicochem Hydrodyn 1982; 3: 57–82.

Gerber

. Inhomogeneous multifluid model for prediction of nonequilibrium phase transition and droplet dynamics. Trans ASME, J Fluids Eng 2008; 130: 031402–1–11.

Wagner

Cooper

Dittmann

et al.

The IAPWS industrial formulation 1997 for the thermodynamic properties of water and steam. Trans ASME, J Eng Gas Turb Power 2000; 122: 150–182.

10.

Gyarmathy G. Grundlagen einer Theorie der Nassdampfturbine. Dissertation, ETH Zürich, Switzerland, 1962.

11.

IAPWS. Revised release on surface tension of ordinary water substance. Moscow, Russia: IAPWS, 2014.

12.

Moses

Stein

. On the growth of steam droplets formed in a Laval nozzle using both static pressure and light scattering measurements. Trans ASME, J Fluids Eng 1978; 100: 311–322.

13.

Moore MJ, Walters PT, Crane RI, et al. Predicting the fog-drop size in wet-steam turbines. In: Proceedings of the IMechE conference on heat and fluid flow in steam and gas turbine plant, Coventry, April 1973, paper no. C37/73, pp.101–109. London: Institution of Mechanical Engineers.

14.

Starzmann

Hughes

White

et al.

Numerical investigation of boundary layers in wet steam nozzles. Trans ASME, J Eng Gas Turb Power 2017; 139: 012606–1–8.

15.

Guha A and Young JB. Time-marching prediction of unsteady condensation phenomena due to supercritical heat addition. In: Turbomachinery: Latest Developments in a Changing Scene, Proc. IMechE. London: IMechE, 1991, pp.167–177.

Modelling of condensing steam flows in Laval nozzles with ANSYS CFX

Abstract

Keywords

Get full access to this article

References