Theory

The heat capacity is evaluated with equation (1). The material library checks it at 51 temperatures across Polynomial temperature range (custom gas) and rejects the material if $c_p$ does not exceed the gas constant anywhere in that range. The program converts the coefficients exactly into the molar polynomial of the solver's janaf thermodynamics (OpenFOAM user guide, 2026); see Heat capacity model (custom gas).

Data published as a molar heat capacity $\bar{c}_p(T)$ in J/(mol K) convert to these coefficients by multiplication by $1000/M$ ; data given as $\bar{c}_p/\mathcal{R}$ (the usual 7-coefficient form) convert by multiplication by $\mathcal{R}/M$ , equation (2).

Equations

c_p(T) = c_0 + c_1 T + c_2 T^2 + c_3 T^3 + c_4 T^4

(1)

c_i = a_{i+1}\,\frac{\mathcal{R}}{M}

(2)

where	meaning	unit
$c_p$	Specific heat capacity at constant pressure	J/(kg K)
$c_i$	Coefficient of $T^i$	J/(kg K^(i+1))
$a_{i+1}$	Coefficient of $T^i$ in the molar form $c_p M/\mathcal{R}$	-
$M$	Molar mass	kg/kmol
$\mathcal{R}$	Universal gas constant, 8314.47	J/(kmol K)

Default and rule

Default: c0 = 1006, others 0
Rule: $c_0 = 1006$ , the others 0 (a constant air value) in a new material.
Source: The polynomial form and its conversion to the janaf coefficients are defined by the program; the janaf form is that of OpenFOAM (OpenFOAM user guide, 2026).

Valid range c_p(T) > R over the whole range

Positive cv

$c_p(T) > R$ at every temperature of the range.

References 1

OpenCFD Ltd. (2026). OpenFOAM user guide. openfoam.com. Web page

Theory

Equations

Default and rule

Valid range c_p(T) > R over the whole range

Related 3

References 1