The main objective of this chapter is to study the liquid film condensation in a thermal desalination process, which is based on the phase change phenomenon. The external tube wall is subjected to a constant temperature. The set of the non-linear and coupled equations expressing the conservation of mass, momentum and energy in the liquid and gas mixtures is solved numerically. An implicit finite difference method is employed to solve the coupled governing equations for liquid film and gas flow together with the interfacial matching conditions. Results include radial direction profiles of axial velocity, temperature and vapour mass fraction, as well as axial variation of the liquid film thickness. Additionally, the effects of varying the inlet conditions on the phase change phenomena are examined. It was found that increasing the inlet-to-wall temperature difference improves the condensate film thickness. Decreasing the radius of the tube increased the condensation process. Additionally, non-condensable gas is a decisive factor in reducing the efficiency of the heat and mass exchanges. Overall, these parameters are relevant factors to improve the effectiveness of the thermal desalination units.
Part of the book: Desalination and Water Treatment