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High-pressure and high-temperature density and vapor-pressure measurements and derived thermodynamic properties of natural waters of Yardymli district of Azerbaijan
Misirkhan Talibov, Javid Safarov, Egon Hassel and Ilmutdin M Abdulagatov

Density of eight geothermal and natural water samples from Yardymli District of Azerbaijan have been measured over the temperature range from (274 to 413) K and at pressures up to 100 MPa. The measurements were made using the Anton Paar DMA HPM and DSA 5000М VTD densimeters. The combined expanded uncertainty of the density, pressure, and temperature measurements at the 95 % confidence level with a coverage factor of = 2 is estimated to be (0.01 to 0.03) %, (0.1 to 0.5) %, and 15 mK, respectively. For the same geothermal and natural water samples the vapor –pressures were also measured using absolute and differential static, at low temperatures from (274 to 323) K, and absolute static methods at high temperatures from (323 to 413) K. The measured vapor-pressures (PS-TS) and single-phase PVT data were used to accurately estimate saturated liquid densities (ρS-TS) for all studied geothermal and natural water samples using extrapolation technique to complete the high-temperature and high-pressure PVT phase diagram of natural waters. The Riedel’s characteristic density constant of the specific ions (ion contribution constants) for main ion species in the natural water samples were estimated on the bases of measured PVT properties. Measured values of density were used to develop equation of state which reproduced the experimental densities within an uncertainty of 0.005 % and can be used for engineering calculation of the other important thermodynamic properties such as adiabatic coefficient of bulk compressibility (KS), isothermal coefficient of bulk compressibility (KT), thermal expansion coefficient (αP), thermal pressure coefficient (𝛾V), internal pressure (Pint), enthalpy difference (ΔH), entropy difference (ΔS), isochoric heat capacity (CV), isobaric heat capacity (CP), and speed of sound (W) of natural waters. The measured values of density of natural waters at atmospheric pressure have been used as a reference data for prediction high-temperature and high-pressure PVT properties. The present high-pressure and high-temperature PVT data for natural waters were used to check and confirm the accuracy, reliability and predictive capability of the predictive methods.

Keywords: equation of state; density; natural waters; thermodynamic properties; vapor-pressure; vibrating tube densimeter

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