Some simplified expressions for the thermal conductivity in an external field

For a polyatomic gas simple expressions have been derived for the thermal conductivity as well as for the variation of the thermal conductivity as a function of an external field. This has been achieved by using the total heat transport as a trial function in the kinetic theory instead of the usual approach in which translational and rotational heat transport are treated separately. For a number of gases a numerical comparison is made between both methods.