The pure species thermal conductivities are computed only for the purpose of later evaluating mixture-averaged thermal conductivities; the mixture conductivity in the multicomponent case does not depend on the pure species formula stated in this section. Here we assume the individual species conductivities to be composed of translational, rotational, and vibrational contributions as given by Warnatz [. ]

(5–17)

where

(5–18)

(5–19)

(5–20)

and,

(5–21)

(5–22)

The molar heat capacity relationships are different depending on whether (or not) the molecule is linear (or not). In the case of a linear molecule,

(5–23)

(5–24)

(5–25)

In the above, is the specific heat at constant volume of the molecule and is the universal gas constant. For the case of a nonlinear molecule,

(5–26)

(5–27)

(5–28)

The translational part of is always the same,

(5–29)

In the case of single atoms (H atoms, for example) there are no internal contributions to , and hence,

(5–30)

where . The " self-diffusion" coefficient comes from the following expression,

(5–31)

The density comes from the equation of state for an ideal gas,

(5–32)

with being the pressure and the species molecular weight.

The rotational relaxation collision number is a parameter that we assume is available at 298 K (included in the database). It has a temperature dependence given in an expression by Parker [40] and Brau and Jonkman, [41]

(5–33)

where,

(5–34)