Thermodynamic properties of standard seawater: extensions to high temperatures and pressures
- 1Lehrstuhl für Technische Thermodynamik, Universität Rostock, Albert-Einstein-Str. 2, 18059, Rostock, Germany
- 2Department of Heat and Refrigeration Techniques, Azerbaijan Technical University, H. Javid Avn. 25, AZ1073 Baku, Azerbaijan
- 3Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, 33149, Miami, FL, USA
- 4Sektion Physikalische Ozeanographie und Messtechnik, Leibniz-Institut für Ostseeforschung, Seestr. 15, 18119 Warnemünde, Germany
- 5Abteilung für Physikalische Chemie, Universität Rostock, Hermannstr. 14, 18051, Rostock, Germany
Abstract. Measurements of (p, ρ, T) properties of standard seawater with practical salinity S≈35, temperature T=(273.14 to 468.06) K and pressures, p, up to 140 MPa are reported with the reproducibility of the density measurements observed to be in the average percent deviation range Δρ/ρ=±(0.01 to 0.03)%. The measurements are made with a newly constructed vibration-tube densimeter which is calibrated using double-distilled water, methanol and aqueous NaCl solutions. Based on these and previous measurements, an empirical expression for the density of standard seawater has been developed as a function of pressure and temperature. This equation is used to calculate other volumetric properties including isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, the thermal pressure coefficient, internal pressure and the secant bulk modulus. The results can be used to extend the present equation of state of seawater to higher temperatures for pressure up to 140 MPa.