The Gravity Controlled Film Condensation of Saturated and Superheated Binary Vapour Mixtures on a Vertical Plate

The gravity controlled film condensation of saturated and superheated binary vapour mixtures on a vertical plate is theoretically treated. Similarity solutions are numerically obtained for ethanol -water and air-water mixtures. It is revealed that the buoyancy force due to temperature difference is important as well as due to concentration difference and convective heat transfer is appreciable for superheated vapour and that the temperature distribution in the vapour boundary layer is markedly affected by the diffusion flux toward the vapour-liquid interface. New correlation equations of heat and mass transfer are derived from the numerical results. These equations can be reduced to the equations of condensation of saturated and superheated pure vapours, simultaneous heat and mass transfer for very small diffusion velocity, and single-phase free convection.