Computer modeling of thermotransport in a uniform binary liquid solution with equimolar n-alkane mixtures

Abstract

By means of molecular dynamics (MD), two novel methods, a thermal mean-path that may outline temperature profiles effectively in the MD system and a modified coarse-grained force field potential (the MCG-FFP) that may depict inter/intra-molecular interactions fairly well among n-alkane species, are employed to simulate a thermotransport process in a uniform liquid solution with two equimolar n-pentane (nC-5) and n-decane (nC-10) mixtures. In addition, all the MD simulations are running under two constraints: a weak thermal gradient exerting on the MD system from its hot through cold boundary sides and the standard-state acting on the MD system from its outer environment. During the whole MD simulations, coefficients of thermal diffusion and mass mutual diffusion, and the Soret coefficient (SC) for the MD system are calculated by using the MCG-FFP. As a result, the MD simulations indicate that nC-5 species with light molar-mass would migrate toward the hot boundary region, while nC-10 species with heavy molar-mass would migrate toward the cold one. Coefficients calculated from the MCG-FFP are found to meet relevant experimental outputs fairly well. Furthermore, an empirical formula developed by means of relevant continuum methods is used for calculating coefficients of mass mutual diffusion in solutions mixing with multimolar nC-5 and nC-10 species. Its one output is found to corroborate pretty well with that from the MD simulations. This may expect that such the formula would perform universally when characterizing properties of mass mutual diffusion in binary liquid solutions with other multimolar alkane mixtures in the petroleum engineering.