EXPERIMENTAL AND CFD INVESTIGATION OF LIQUID FLOW OUTSIDE EVAPORATION TUBES AND ITS INFLUENCE ON HEAT TRANSFER

Liquid film flow significantly affects distillation, which directly determines the heat transfer coefficient. This study investigates the effects of flow patterns, as well as of heat and mass transfer on the vapor-liquid interface, on the heat transfer in a horizontal-tube falling-film evaporator. Related data are acquired through simulation and experiment. A volume of fluid model coupled with a user-defined function module was adopted to simulate a liquid-vapor system. In addition, an experimental apparatus and its principal characteristics were introduced. This method was used to test the extended droplets on the tube surface, the flow patterns, and the effect of liquid film state on heat transfer. Simulation results show good agreement with the experimental results, with both having a deviation band within 10%. A computational method suitable for simulating liquid-steam flow is established. Both simulation and experimental results indicate that 0.08kg/( m-s) of sprinkling density is the breakpoint of liquid outside a tube from columnar flow to sheet flow, and the overall coefficient of heat transfer K under the experimental conditions reaches up to 4.06 kW/m(2) K. This value is significant in guiding the design of the spraying density of low-temperature multieffect seawater desalination devices. Thus, this research provides a basis for the further improvement of heat transfer performance.