Evaporation heat transfer of falling films on horizontal tube. Part 1: Analytical study

Abstract

Evaporation heat transfer of a saturated falling film on a horizontal tube was studied analytically. For laminar flow, a model comprised of the developing, transitional, and developed regions is proposed. The boundary layer integral method was used to reach a closed-form solution. A third-order polynomial temperature profile was assumed in the developing region, and a linear profile in the developed region. Both profiles join smoothly in the transition region. From this analysis, the Nusselt number was presented as a function of film Reynolds number, Prandtl number, and dimensionless tube radius. A similar correlation was developed for turbulent flow using the eddy viscosity model, where the Nusselt number was obtained as a function of film Reynolds number and Prandtl number.