Thermodynamic Properties of Heated Air

This sample employs the Chemked program units for calculation of mean gas parameters. The properties of abruptly heated air at fixed pressure and fixed temperature is considered.


Input values

Pressure: 1 atm
Interval of initial temperatures: 298 - 4000K

Air composition: [N2]0 : [O2]0 : [Ar]0 : [CO2]0 = 78.084 : 20.9476 : 0.9365 : 0.0319

 

Solution

The calculations have been made to equilibrium states; some profiles for T=3000K are shown in Fig. 1.


 

Fig 1. Species mole fractions, the enthalpy H (kJ/mol) and the heat capacity Cp (J/K mol); T0 = 3000k, P = 1atm

 

Mixture-averaged gas parameters (the enthalpy, the heat capacity and the molecular weight)  are shown in Fig. 2 as functions of temperature for initial and equilibrium gas mixtures.

 

Fig 2. The enthalpy and the heat capacity vs. temperature, lines – this simulation, points – calculation from the polynomials [1]

 

In Fig. 2, the thermodynamic properties of air for initial gas mixture (non-dissociated air) are compared with the independent calculations from the polynomials [1] (presented below). The calculations were made using the standard NASA formulas.

 

AIR           L 9/95                  0.G   200.000  6000.000  B  28.96518     1

 3.08792717E+00 1.24597184E-03-4.23718945E-07 6.74774789E-11-3.97076972E-15    2

-9.95262755E+02 5.95960930E+00 3.56839620E+00-6.78729429E-04 1.55371476E-06    3

-3.29937060E-12-4.66395387E-13-1.06234659E+03 3.71582965E+00-1.50965000E+01    4


References

[1] Alexander Burcat, Ideal Gas Thermodynamic Data in Polynomial Form for Combustion and Air Pollution Use. http://garfield.chem.elte.hu/Burcat/burcat.html