Research Of Liquid-solid Two Phase Flow In Bittern Transfer Pump With Crystallization Phenomenon And Optimum Design Based On Population Balance Model

The two-phase flow associated with crystallization is a common phenomenon in industry.Crystallization appears during salt aqueous solution transportation,which has a negative impact on relevant equipment operations and even causes severe losses.Bittern transfer pump has a very wide range of applications in industry as an important fluid conveying device.Therefore,it is of great guiding significance to research two-phase flow associated with crystallization in bittern transfer pump in the academic study and engineering application.In order to understand the two-phase flow with crystallization in the pump more deeply,but the traditional CFD numerical simulation did not take into account the microscopic phenomena of particles,so this method is not reasonable for two-phase flow with crystallization.Unedr the support of Six talent peaks project in Jiangsu Province(2014-ZBZZ-016),a bittern transfer pump was designed as research object in this paper,population balance model(PBM)coupled with mixture two-phase model and user-defined crystal growth and nucleation models were used in this study.The main work and achievements are as follows:1.Present research states of the two-phase flow with crystallization and optimal design method of impeller at home and abroad were introduced.The microscopic behavior of salt-out crystal particles were elaborated.The growth of crystals was found to include surface energy effects,which are controlled by the energy requirements of the smallest surface.Under normal circumstances,during the growth process,the level of supersaturation determines whether the solute diffusion process or the surface reaction process plays a decisive role in crystal growth.2.The theoretical knowledge of population balance model was summarized.Considering the effects of particle size and supersaturation on growth and nucleation,the appropriate growth and nucleation models for salting out crystals were chosen to lay the theoretical foundation for the next numerical calculation.3.Three-dimensional modeling software Pro/E was applied to sculpt the centrifugal pump.The unstructured grids were generated in the area of flow passage in the pump.The two-phase flow field of salting out of the centrifugal pump was simulated with CFD-PBM two-way coupling method and the results are verified by experiments.It was found that the average particle size of the crystal particles,pump head and efficiency were closer to the experimental value compared with the original PBM model,which only consider the coalescence and the broken phase.4.Based on previous research,a bittern transfer pump was designed as research object to simulate operating conditions under different flow rates and different solid volume concentrations.It was found that the average particle size of the particles gradually decreased from the inlet of the impeller and then gradually increased,reaching the maximum at the outlet.5.The Box-Behnken design method was used to design the three structural parameters of the impeller.Multi-objective optimization was performed by the response surface method to obtain the regression equation of the head,efficiency,large particle size particle density,and the optimal solution was finally confirmed.The optimization model were compared with the original model,which showed the feasibility of the response surface method to optimize the two-phase flow with crystallization in the bittern transfer pump.