Modeling investigation on the thermal conductivity of saturated vapor

A general analytical equation to predict thermal conductivity of saturated vapors has been expressed. It was started with a global energy transfer equation which rearranged by molecular heat capacity and density. Then we replaced speed of sound and a new parameter as characteristic length of energy, Λ, instead of heat transfer velocity and mean free path, respectively. The values of Λ for ideal gases showed a linear correlation to molar volume with a material dependent slope behind the σ (molecular diameter) parameter. However, considering different materials in the saturated vapor state, say 14, including monatomic and polyatomic as non-polar, polar and polar-protic substances concluded a linear relation for Λ value versus reduced molar volume. It is noticeably found that for saturated vapor the Λ value and then the final equation for thermal conductivity can be considered independent of material type.