The effect of mass transfer on the heat-transfer coefficient (HTC) in evaporation of ternary liquid films inside a vertical tube was experimentally studied. The triangular diagram of the ratio h(exp)/h(id) as a function of the liquid compositions, based on our own experimental data for the system methanol-isopropanol-water and the corresponding binary systems, is presented. The calculation results of HTC from the model equations, taking into account the mass-transfer coefficients in a liquid film, were compared with experimental data for the systems studied. Different assumptions in model matrix equations were applied and these effects on calculated HTC values analysed. (C) 2003 Published by Elsevier B.V.