The Thermal Conductivity of Hydrogen, Deuterium and Their Mixtures Near Room Temperature within the Pressure Range 2 36 MPa

The paper reports new, absolute measurements of the thermal conductivity of hydrogen and deuterium as well as of two binary mixtures of the two components at 27.5°C. The measurements have been carried out as a function of density in a transient hot‐wire instrument and extend over the pressure ranges 2  13 MPa for the mixtures and 2  36 MPa for pure hydrogen. The uncertainty in the absolute thermal conductivity data is estimated as one of ±0.2%. The measurements have been arranged so as to yield the ratio of the thermal conductivities of the two pure gases with essentially the same uncertainty.  The Eucken factors for the two pure hydrogen isotopes at zero density have been derived and differ from each other by as much as 1.8% which is well beyond experimental uncertainty. The existing kinetic theory expressions for the Eucken factor of a polyatomic gas are not able to account for this difference. On the other hand the first density coefficients for the thermal conductivity of the two hydrogen isotopes are found to be the same within the limits of experimental error.