Probing free jet expansions of supercritical fluids
Phys. Scr. 80 (4), 048127, October 2009
Submitted to Cluster Science: 31 October 2009
Last Update: 6 January 2011

OA Status: unknown


Attempting to improve the comprehension of supersonic molecular beams at elevated pressures we present a comparative study of thermodynamic descriptions of the terminal flow velocity in free jet expansions. As model system we choose carbon dioxide due to its widespread utilization in supercritical fluid technology. Numerical results for the thermodynamic quantities are obtained using a high accuracy equation of state explicit in the Helmholtz free energy. The influence of pressure and temperature on the beam velocity is investigated for a broad range of stagnation conditions. A consistent physical picture is obtained for calculations employing the initial and final molar enthalpies, while enormous discrepancies are found for descriptions based on the molar isobaric heat capacity or the heat capacity ratio. The deviations are particularly pronounced at the gas–liquid phase transition and in the vicinity of the critical point and can be related to the diverse assumptions of ideal gas behavior. It is shown that computations using real fluid enthalpies permit to assess the fraction of condensation in supersonic jets.


Document Type theoretical
Research Field Thermodynamics and Phase Transitions
PACS 82.33.De
PACS 82.60.Cx
PACS 82.60.Hc
PACS 82.60.Lf
PACS 82.60.Fa