Abstract
A re-evaluation of the second virial coefficient of steam is presented in the paper. The work is a part of broader effort to develop a formulation of the properties of dry and metastable steam suitable for CFD computations. The re-evaluation follows up previous work by Harvey and Lemmon [1], however with a special care for the lower temperature region close to the triple point and including more experimental data. The second virial coefficient was evaluated from volumetric (pvT) data, calorimetric measurements for saturated vapor, steam expansion experiments (measurements of the Joule–Thomson coefficient and the isothermal throttling coefficient) and measurements of the speed of sound. To accurately evaluate the uncertainty of calorimetric measurements, the uncertainty of the temperature derivative of the saturation pressure was determined based on refitting of the IAPWS saturation pressure formula to the experimental data. In the second step, the evaluated data and their uncertainties were used to develop an analytical formula to compute the second virial coefficient as function of internal energy in a range corresponding to the ideal-gas temperatures from 273.16 K to 1073.15 K. The choice of internal energy and density as independent variables is required for the CFD computations to avoid time-consuming iterations.
Highlights
To accurately evaluate the uncertainty of calorimetric measurements, the uncertainty of the temperature derivative of the saturation pressure was determined based on refitting of the IAPWS saturation pressure formula to the experimental data
A new formulation of thermodynamic property of steam and water designed for CFD computation [2] describes residual entropy as a function of density and internal energy in the form of a virial equation
The lower temperature region is usually out of interest because of a little difference of steam properties from the ideal gas ones on the other hand, the metastable region connected with the low temperature region in direction of increasing density lies in centre of low-pressure turbine interests [3]
Summary
A new formulation of thermodynamic property of steam and water designed for CFD computation [2] describes residual entropy as a function of density and internal energy in the form of a virial equation. The virial coefficients as the function of internal energy instead of thermodynamic temperature are required. There is another need for re-evaluation of the virial coefficients. The accuracy of virial coefficients is critical to proper description of the metastable region because of the multiplicative affect of virial coefficients error on the thermodynamic property accuracy The re-evaluation of second virial coefficient is focusing on correct interpretation of its uncertainty with main interest in the lower temperature region where measured data are scarce
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