Thermal equation of state for real gas in a wide range of state parameters, including the critical region
A.B. Kaplun1, B.I. Kidyarov2, A.B. Meshalkin3, A.V. Shishkin4
1 Kutateladze Institute of Thermophysics SB RAS, kaplun@itp.nsc.ru
2 Kutateladze Institute of Thermophysics SB RAS
3 Kutateladze Institute of Thermophysics SB RAS
4 Kutateladze Institute of Thermophysics SB RAS
Keywords: equation of state, compressibility factor, critical region, heat capacity, carbon dioxide, helium-4
Pages: 359-368
Abstract
The compressibility factor was calculated in a wide range of parameters including the critical region using the equations of state obtained previously for real gas and conditions and limitations formulated by the authors for the form (structure) of the equation of state. It was determined that maximal deviations of compressibility factor values calculated by these analytical equations from the experimental (tabulated) values occur mainly within the critical region. A corresponding correction was introduced into the initial equation, and the analytical equation accurately describing experimental data in a wide range of real gas state parameters, including the critical region, was derived. It was shown by the example of analysis of high-accuracy experimental data on thermal properties of helium in the critical region that data description by the proposed analytical equation is at least as good as that obtained by the equation of fluctuation theory (scaling). It is shown that the proposed equation meets the classical conditions at the critical point.
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