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 βcommonβ 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]

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

Usageπ

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 []

Source code