Numerical simulation analysis of heat and mass transfer of saline wastewater in a falling film evaporation tube based on different inlet modes

Abstract

Falling film evaporation technology is widely used in the treatment of salt-containing wastewater in coal chemical industry. However, there is still a lack of research on the inlet method of vertical falling film evaporation tubes. In this paper, the heat and mass transfer processes of saline wastewater under vertical and tangential inlets were investigated using numerical simulations. On this basis, the differences in flow and heat transfer processes between saline wastewater and pure water under tangential inlet were investigated. The results showed that the flow velocity of saline wastewater with a falling film evaporation tube in a tangential inlet mode was larger. Meanwhile, the turbulence in this way was more intense and the fluid temperature in the vertical tube was higher. Saline wastewater has higher temperature and smaller liquid volume fraction than pure water liquid membrane in the range of 193–1,000 mm from the inlet. The use of tangential inlet method to treat salt-containing wastewater has higher evaporation efficiency and is a very effective way to guide the improvement of heat transfer efficiency. HIGHLIGHTS Study on the heat transfer of a falling film evaporator tube with different inlets.; The liquid film velocity at the tangential inlet is faster than that at the vertical inlet.; Salty wastewater is thinner than pure water, which is more conducive to evaporation.;

Keywords

• saline wastewater
• pure water
• falling film evaporation
• vertical tube
• mass and heat transfer