Density, sound speed and derived thermophysical properties of n-nonane at temperatures between (283.15 and 473.15) K and at pressures up to 390 MPa

Abstract

Abstract In this paper, we present density and speed-of-sound experimental measurements for n-nonane at temperatures between (283.15 and 473.15) K and pressures up to 68 MPa and 390 MPa respectively. The density measurements were performed with a vibrating-tube densimeter and the speed-of-sound measurements were carried out in a dual-path pulse-echo apparatus. The vibrating-tube densimeter was calibrated using pure helium and water over the full range of temperature and pressure investigated, while the speed-of-sound apparatus was calibrated using pure water at low pressure over the full range of temperature. The expanded relative uncertainties of the measurements were 0.08% for density and between (0.1 and 0.3)% for sound speed at 95% confidence. The density data were correlated with the modified Tait equation over the entire temperature and pressure range, with an absolute average relative deviation of 0.006%. An empirical equation was developed to represent the sound speed data with an absolute average relative deviation of 0.03%. Both sets of data were compared with the predictions from the equation of state developed by Lemmon and Span. Comparisons have also been made with the available literature and satisfactory agreement was found. Correlations were developed for the density and isobaric heat capacity of the liquid as functions of temperature at a reference pressure of 0.1 MPa, the latter based on literature data. Combining these correlations with the sound-speed surface, properties of the liquid were computed by thermodynamic integration up to a pressure of 390 MPa. Density, isobaric heat capacity, isothermal compressibility and isobaric expansivity values are reported, and their uncertainties were carefully investigated.