In this paper the author develops an algorithm on the basis of heat and thermodynamics theory, to predict data for film condensation on horizontal integral—fin tubes for R32/R134a and R32/R125 mixtures in 25/75, 50/50 per cent compositions by mass correspondingly. Emphasis is focused on the presentation of thermophysical properties of the blends involved in the process considered, i.e. liquid density, viscosity, surface tension, thermal conductivity and latent heat of vaporization. The main point of this work is to define with computational techniques the blend with the most favourable composition, as an environmentally acceptable solution for R22 replacement in some shell-side condensers. Copyright © 2001 John Wiley & Sons, Ltd.