Performance And Mechanism Of Multi-field Coalescence Of Droplets In Gas-liquid Heterogeneous System

With the rapid development of our economy and the pursuit of a better life for people,the contradiction between the sharp increase in freshwater consumption and the current situation of water shortage is becoming increasingly apparent.The immediate priority is to develop efficient water-saving technology and multiple ways to obtain freshwater resources.In the process of industrial modernization,industrial fog as an important freshwater resource has been gradually valued.Capturing industrial fog can not only recover fresh water,but also achieve certain environmental and social benefits.In order to capture industrial fog,firstly,the dynamics of the movement and coalescence of water droplets under electric field in the air atmosphere was studied by theoretical calculation and numerical simulation.Then,a new multi-field coalescence demisting and water recovery device which integrated electric coalescence and fibrous coalescence technology was designed.Finally,it was studied including the gas-liquid separation effect of different parameters of PEF and gas-liquid mixture on the multi-field coalescence device,the size of water droplets in the gas-liquid mixture flowing out of the electric field coalescence unit,the pressure drop and its influence factors of the multi-field coalescence device.The results showed that the deformation of a single uncharged micro water droplet in the air atmosphere caused by the polarization under electric field was very small,and after charging,the water droplet could move due to the electric force.The acceleration and velocity of charged water droplet were related to the droplet diameter,the strength of electric field and the frequency and duty cycle of PEF.The electric field could promote the coalescence of two water droplets and shorten the coalescence time.The reduction of coalescence time was influenced by the droplet diameter,the center distance between two droplets and the strength of electric field.The high duty cycle,frequency and voltage were beneficial to the gas-liquid separation performance of the multi-field coalescence device.The water recovery efficiency of the multi-field coalescence device with PEF applied could be increased to 95.13%from 85.33%with no electric field applied.When the total liquid water concentration and the flow rate of the wet air flow were 105g/m~3 and 4m~3/h respectively,the water recovery efficiency of the multi-field coalescence device could exceed 95%and the liquid concentration of the outflow was only 5.08/m~3.The PEF coalescence unit could promote the coalescence of water droplets and increase the average droplet size from 2.869μm to 4.881μm.The total pressure drop of the multi-field coalescence device depended on the pressure drop of the microfibers coalescence unit and increased with the rise of the total liquid water concentration and the flow rate of the wet air flow.This thesis opened up a new method for efficient water recovery from industrial fog discharged by the wet cooling tower.