TEMPERATURE-DEPENDENCE OF THE THERMAL-CONDUCTIVITY FOR 2 MODELS OF LIQUID BUTANE

We study the temperature dependence of the thermal conductivity of liq uid butane on the atmospheric pressure isobar for the Ryckaert-Bellema ns and anisotropic united atom models of butane by non-equilibrium mol ecular dynamics simulation methods. Expressions for the pressure tense r and the heat flux vector in the molecular representation for the AUA (2) model are derived, and our heat flow algorithm for the calculation of thermal conductivities of interaction site model molecules is modi fied to apply to the AUA(2) model. We find that the RE model systemati cally 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) mode l gives better results than the RE model near the boiling point, diffe ring from experiment by only 7%, but it becomes very difficult to simu late near the freezing point and poor results are obtained for the two lowest temperatures due to inadequate sampling of phase space.