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The janaf model provides thermodynamic property characteristics as a function of temperature. The model is based on two sets of coefficients that describe the property variation with temperature above, and below, the model ‘common’ temperature, \(T_{\text{common}}\), i.e.

\[\mathrm{coeffs} = \begin{cases} \mathrm{low} & \text{if}\, T \gt T_{\text{common}} \\ \mathrm{high} & \text{otherwise} \\ \end{cases}\]

The functions are valid within the range \(200 \lt T \lt 6000 \; \text{[K]}.\)

If the bounds are exceeded, calculations will fail with a fatal error.

Heat capacity at constant pressure, \(c_p\) [J/kg/K]

\[c_p = c_1 + c_2 T + c_3 T^2 + c_4 T^3 + c_5 T^5 + c_{p, eos}\]

Absolute enthalpy, \(H_a\) [J/kg]

\[H_a = c_1 T + \frac{c_2 T^2}{2} + \frac{c_3 T^3}{3} + \frac{c_4 T^4}{4} + \frac{c_5 T^5}{5} + H_{eos}\]

Entropy, \(S\) [J/kg/K]

\[S = c_1 \ln T + c_2 T + c_3 \frac{T^2}{2} + c_4 \frac{T^3}{3} + c_5 \frac{T^4}{4} + c_6 + S_{eos}\]

Usage

The janaf thermodynamics model is defined using the entries:

thermodynamics
{
    Tlow            <scalar>;
    Thigh           <scalar>;
    Tcommon         <scalar>;
    lowCpCoeffs     (<scalar> <scalar> <scalar> <scalar> <scalar> <scalar> <scalar>);
    highCpCoeffs    (<scalar> <scalar> <scalar> <scalar> <scalar> <scalar> <scalar>);
}

Where

  • Tlow : Low temperature limit [K]
  • Thigh : High temperature limit [K]
  • Tcommon : Common temperature [K]
  • lowCpCoeffs : Low coefficients []
  • highCpCoeffs : High coefficients []

Further information

Source code