A reference equation of state for the thermodynamic properties of nitrogenfor temperatures from 63.151 to 1000 K and pressures to 2200 MPa

A new formulation for the thermodynamic properties of nitrogen has been dev eloped. Many new data sets have become available? including high accuracy d ata from single and dual-sinker apparatuses which improve the accuracy of t he representation of the p rhoT surface of gaseous, liquid, and supercritic al nitrogen, including the saturation states. New measurements of the speed of sound from spherical resonators yield accurate information on caloric p roperties in gaseous and supercritical nitrogen. Isochoric heat capacity an d enthalpy data have also been published. Sophisticated procedures for the optimization of the mathematical structure of equations of state and specia l functional forms for an improved representation of data in the critical r egion were used. Constraints regarding the structure of the equation ensure reasonable results up to extreme conditions of temperature and pressure. F or calibration applications, the new reference equation is supplemented by a simple but also accurate formulation, valid only for supercritical nitrog en between 250 and 350 K at pressures up to 30 MPa. The uncertainty in dens ity of the new reference equation of state ranges from 0.02% at pressures l ess than 30 MPa up to 0.6% at very high pressures, except in the range from 270 to 350 K at pressures less than 12 MPa where the uncertainty in densit y is 0.01%. The equation is valid from the triple point temperature to temp eratures of 1000 K and up to pressures of 2200 MPa. From 1000 to 1800 K, ti le equation was validated with data of limited accuracy. The extrapolation behavior beyond 1800 K is reasonable up to the limits of chemical stability of nitrogen, as indicated by comparison to experimental shock tube data. ( C) 2001 by the U.S. Secretary of Commerce on behalf of the United States. A ll rights reserved.