Estimation of the thermodiffusion coefficients for dodecane/n-butane/ methane mixtures and comparison with experimental data from foton M3 mission

Two different ternary mixtures of methane, n-butane and n-dodecane at a high temperature and pressure have been studied in micro-gravity conditions to understand the thermal diffusion process. It was found that in both mixtures n-dodecane separated to the cold side whereas methane segregated to the hot side, n-butane, the species with an intermediate density, showed a variation in the separation direction. More precisely, at low concentration it collected on the hot side but separated to the opposite direction when its mole fraction was increased. A combination of the relative density and the mixture composition has been presented as a reason.