Thermodynamic Properties of Air at Pressures to 2000 MPa
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Abstract
A new formulation for the thermodynamic properties of standard dry air at pressures to 2000 MPa has been developed. This formulation, which can be used at temperatures from the freezing liquid line to 2000 K, is based on comprehensive experimental measurements of densities, heat capacities and sound speeds at lower pressures and temperatures and on the use of corresponding states to calculate the properties of air from nitrogen data at high pressures and temperatures. The experimental and calculated properties were then used in a regression analysis to develop a fundamental equation for standard air with a nominal mole fraction composition of 0. 78 N<SUB>2</SUB>+0. 21O<SUB>2</SUB>+0. 01 Ar. In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the fundamental equation for the vapor is ±0. 1%; the uncertainty in calculated liquid densities is ±0. 2%. The estimated uncertainty of calculated heat capacities is ±1%, and that for calculated speed of sound values is ±0. 2%. At temperatures above 873 K and 100 MPa, the estimated uncertainty of calculated density values is ±0. 5%.
Journal

 The Review of High Pressure Science and Technology

The Review of High Pressure Science and Technology 7, 11711176, 1998
The Japan Society of High Pressure Science and Technology