Detailed thermal desalination analysis of a falling film on a horizontal tube using a sharp-interface elliptic numerical model

An in-house code is utilized to simulate the evaporation from falling films of fresh water and salt water over an isothermal horizontal tube. Full elliptic governing equations for the liquid and gas phases are solved employing a two-dimensional, two-phase model. This modelling represents a significant advancement in the simulation of the evaporation phenomenon that employs innovative methods to precisely determine the location of the liquid and gas interface, the mass transfer in the system, and address the occurrence of the supersaturation phenomenon in the mixture phase. It is also capable of capturing reverse flow and recirculation zones. A sharp interface model is used that determines the evaporation rate using an energy balance at the interface. The accuracy of the model is verified by comparing the present results with relevant experimental and numerical data available in the literature. New numerical results are provided for a parametric study examining how variations in inlet salt mass fraction, inlet pressure, inlet mixture Reynolds number, wall temperature, and inlet liquid mass flow rate affect the falling film development, heat transfer, and evaporation rate around the tube.