Numerical investigation of falling film generation outside vertical tube with ammonia-water nanofluid

This paper constructed a mathematical model of ammonia-water nanofluid falling film generation outside the vertical tube, which considers the change of the film thickness of the falling film solution, the thermal convection along the film thickness direction and the physical properties of the solution. By solving the mathematical model, the temperature field and other elements of the liquid film were determined. The influence of the properties of the working fluid on the heat and mass transfer in the falling film process is investigated. According to the calculation results, a method of adding nanoparticles in the process of ammonia falling film generation is proposed. The simulation results showed that the heat efficiency of entire falling film process can be enhanced by adding an appropriate amount of Al₂O₃ nanoparticles_. When the added Al₂O₃ nanoparticles are 1 vol.%, the coefficient of the heat transfer is increased by about 4%, and the mass transfer effect is also improved by about 12%. In brief, the establishment of this model aims to improve heat and mass transfer efficiency and promote the application and integration of low-grade waste heat or renewable energy technologies in built environment.