Heat Transfer Research Of Falling Film Evaporation And Process Simulation Of Multi-Effect Distillation System

Vertical falling film evaporator has high heat transfer coefficient, low temperature difference, and has been extensive applied. This paper aims to develop high effective equipment to decrease the heat consumption.The minimal sprayed density is 35kg/h, saw-tooth and cone liquid distributors can greatly improve the effect of falling film.The falling-film evaporation heat transfer coefficient is calculated under various conditions with heat flux from 13 to 90 kW·m2, heat transfer temperature difference from 2.87 to 9.5℃, and liquid Reynolds number from 4500 to 15000. The experimental results of porous tube, spiral tube and corrugated tube are compared. The results show that:the porous tube has lower temperature difference and better performance than other enhanced tubes. The heat transfer coefficient is 100% higher than that of smooth tube. The porous tube still keep excellent performance in salt water, so it is available to be applied in MED system.To simulate the multi-effect distillation system with Aspen Plus, the results show that:The system of parallel feed has high gain out ratio, recovery ration and concentrate ratio. The system GOR of parallel feed can have greatly increase when extracting part of outlet steam.