A comparison of experimental and theoretical values of the thermal conductivity of binary mixtures of nitrogen and hydrogen

Abstract

Recent experimental measurements of the thermal conductivity of mixtures of nitrogen and hydrogen are compared with values calculated from Hirschfelder’s theory of the transport of heat in mixtures of polyatomic gases. The discrepancies between theory and observation, though small, appear to be greater than the experimental error; the observed thermal conductivities almost always exceed the theoretical values. Similar small discrepancies have been reported in some other experimental work. It is shown that for mixtures of nitrogen and hydrogen the discrepancies are unlikely to be due to a failure to assign correct values to the parameters appearing in the theroretical equations. Attention is therefore drawn to the validity of the assumptions underlying the theory. Hirschfelder’s theory distinguishes translational and internal contributions to the conductivity of the mixture. It rests on the assumption, originally due to Eucken, that the translational contributions to the thermal conductivity of the individual constituents may be calculated as if the gases were monatomic, i.e. by setting K trans. = 2·5 nc v trans. .It is suggested that this is an overestimate of the translational contribution and that complete accuracy is therefore not to be expected from calculations based on Hirschfelder’s theory. A recent theoretical study by Mason & Monchick is in accord with this suggestion.