Heat Transfer Modeling in Downflowing Films

The manuscript deals with heat transfer in two phase flows in industrial film evaporators. The results of mathematical and physical heat transfer modeling to the films of saturated water and water solutions are presented. The films that were analyzed are downflowing on the vertical heated surfaces, having turbulent and laminar structures with the developed wavy surface. The analyses has been carried out for the regimes of evaporation from the interphase and nucleate surface boiling. The developed heat transfer model represents heat transfer as a cyclic process of temperature field relaxation at the conditions of periodic mixing of the bulk of the film by large waves. The analytic correlations obtained allow to calculate the temperature field in the liquid characterized by the developed wavy structure at the films free falling or together with co-current steam core. The integral characteristics of heat transfer have been derived. The simplified correlations for engineering calculations are presented. The presented work can be recommended for the engineering and research stuff engaged in the design calculation of industrial film evaporators.