Re-evaluation of experimental data on the second virial coefficient for steam and development of its analytical representation as a function of the internal energy

Institute of Thermomechanics AS CR, v.v.i, Dolejškova 5, 18200 Prague 8, Czech Republic

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.