Thermal conductivity of liquids and gases

In this article on fluid thermal conductivity data, we have tried to gather the most credible values from the literature. The accuracy of these data is never better than 1%; however, even for the most common fluids, discrepancies between experimental data can reach several percent, so great care must be taken when using these tables.

With very few exceptions, the thermal conductivity of gases increases with temperature; that of liquids, on the other hand, decreases. Any other change is often due to the radiation effect, which is difficult to estimate for partially transparent fluids, and sometimes to convection.

The thermal conductivity of fluids also varies with pressure. As pressure rises, the thermal conductivities of gases and liquids increase. This variation with pressure is quasi-linear in some regions of the phase diagram, e.g. for low-density gases near atmospheric pressure, or for liquids far from the critical region. In the critical region of a fluid, thermal conductivity increases very rapidly, and its variation along the critical isochorus shows infinite divergence at the critical temperature; its behavior is analogous to that of the heat capacity at constant pressure. There are few experimental data in this field and few practical calculation methods, so we won't deal with this case.

Mixtures that are not p lus will not be considered. The mixing law of heat conduction is rarely linear, especially if the molecules have very different masses and are in different thermodynamic states.