HEATING AND EVAPORATION OF TURBULENT FALLING LIQUID-FILMS

Falling film heat exchangers find wide application in industry. In this work an analysis of heat transfer in turbulent falling films is presented. The objective is to develop a single analytical formula for the fully developed heat transfer coefficient for the cases of evaporation (or condensation) and heating (or cooling). In the model developed the turbulent transport near the wall is described by a modified Van Driest equation for the eddy diffusivity as proposed by D. T. Hanna et al. This expression was further modified here for turbulent transport in falling films using the reduction factor suggested by H. Limberg and recommended by R. A. Seban. The resulting eddy diffusivity expression is similar to the Nikuradse distribution.