Numerical investigation of falling film evaporation of multi-effect desalination plant

In this study, a numerical investigation is performed to improve the heat transfer and pressure drop of falling film evaporator using multiphase flow formulations in Eulerian–Eulerian approach. A finite volume method code is used for solving the governing equations including continuity, energy and Reynolds averaged Navier–Stokes equations (RANS) with the k–ε turbulence model. Also, the heat and mass transfer during the phase change is taken into account. The effects of temperature difference, arrangement of tubes and tube pitch on the average heat transfer coefficient, the net vapor production and pressure drop across the tube bundles are presented. The results show that increase of temperature difference increases vaporization rate, heat transfer coefficient and pressure drop along the tube bundle. It is also found that the heat transfer coefficient for vertical arrangement of tubes is larger than that of horizontal arrangement.