Heat, mass and momentum transfer of a water film flowing down a tilted plate exposed to solar irradiation

This paper has investigated the heat, mass and momentum transfer of a water film falling over a tilted plate with solar radiant heating and water evaporation. A cluster of physical models which include conduction, convection with flow turbulence, diffusion, radiation and phase change was developed for predicting the characteristics of heat, mass and momentum transfer. A fully implicit control-volume finite-difference procedure was used to solve the coupling equations. The effects of various parameters on heat, mass and momentum transport were investigated. The results revealed that the gradients of temperature and the mass fraction of water vapor in the gas layer, and the wind velocity played a key role in the heat and mass transfer along the gas-water interface. The water film Reynolds number related to the film thickness and the plate tilt angle markedly exerted an influence on the eddy viscosity and the turbulent Prandtl number of the water film. The ambient atmospheric temperature only dramatically affected the interfacial sensible heat transfer. The magnitude of solar incident flux had intense influence on the water film temperature but not on the interfacial heat and mass transfers.