液-固两相流热交换器内的防除垢研究

Study on Anti-fouling and Scale Prevention in Liquid-solid Two-phase Flow Heat Exchanger

为了脱除附着在换热管壁面的污垢,研究了换热管中污垢剥除所需的碰撞次数,探讨了液-固两相流污垢剥除所需的时间。基于液-固两相流固体颗粒与污垢层多次碰撞对防除垢的作用,建立了液-固两相流防除垢模型,采用EDEM-FLUENT耦合,模拟计算换热管内非稳态液-固两相流动,探索换热管内固体颗粒的分布情况和碰撞分布。结果表明,颗粒在换热管中分布较为均匀;污垢被剥除需要经过多次碰撞,碰撞次数随循环流速的增大而减少,随固体颗粒粒径的增大而增加,与固体颗粒的体积分数基本无关,在最佳防除垢状态下需要经过5～8次的碰撞;适当增加循环流速和固体颗粒体积分数,同时减小颗粒的粒径可以加快污垢的剥除速度。

In order to remove the scale and fouling attached on the wall of the heat exchange tube, the collision times of fouling stripping in heat exchanger tube were studied and the duration required to remove fouling in liquid-solid two-phase flow was discussed. Based on the multi-collision performance between solid particles in liquid-solid two-phase flow and dirt layers, a liquid-solid two-phase flow anti-scaling model was established and the two-phase flow was simulated by using EDEM-CFD on the solid particles and collision distribution inside the heat exchange tube. The results show that the particles in heat transfer tube is uniformly distributed and the multi-collisions are required to remove the scale inside. The number of collisions decreases with the increasing of circulating velocity, and increases with the increasing of particle size, while not much related to the volume fraction of solid particles. The scale removing ratio could be improved by increasing the circulation velocity and the volume fraction of solid particles with decreased the particle size.