Temperature dependence of the thermal conductivity for two models of liquid butane Original Research Article

We study the temperature dependence of the thermal conductivity of liquid butane on the atmospheric pressure isobar for the Ryckaert-Bellemans and anisotropic united atom models of butane by non-equilibrium molecular dynamics simulation methods. Expressions for the pressure tensor and the heat flux vector in the molecular representation for the AUA(2) model are derived, and our heat fkow algorithm for the calculation of thermal conductivities of interaction site model molecules is modified to apply to the AUA(2) model. We find that the RB model systematically underestimates the thermal conductivity of butane by 14% at the highest temperature (the boiling point), with the discrepancy growing to 19% at the lowest temperature (the freezing point). The AUA(2) model gives better results than the RB model near the boiling point, differing from experiment by only 7%, but it becomes very difficult to simulate near the freezing point and poor results are obtained for the two lowest temperatures due to inadequate sampling of phase space.