Numerical analysis and optimization of falling film evaporation with tangential inlet for saline wastewater treatment

Both the flow state of the liquid film and the heat transfer effect all affected the efficiency of falling film evaporation directly. In this study, based on computational fluid dynamics and orthogonal tests, numerical simulations were performed for different inlet velocities, inlet temperatures, and upper and lower tube diameter ratios of evaporation tubes with tangential inlet methods. Results showed that the tangential inlet method makes the liquid film distributed evenly. The increase in the ratio of upper and lower pipe diameters could enhance the heat transfer effect. When it was 1.5:1, the export salt concentration increased to 5.87%. When the inlet velocity increased, the heat transfer effect became better. The inlet temperature had a positive effect on the heat transfer effect. The orthogonal test results showed that when the upper and lower tube diameter ratio was 1.5:1, the inlet flow rates reached 0.4 ​m/s and the inlet temperature was 303 ​K, the flow distance increased by 6.98%.