Research On The Characteristics Of Fluidization Of Wet Particles With The Influence Of Interstitial Fluid

The process of particle fluidization is closely related to the daily production activities,various kind of craftworks are realized by the fluidization of particles,especially in the process industry.Peaple begin to carry out sorts of research on the characteristics of particle-fluid system from the beginning of 20 th century,they try to establish the mathematical model of two-phase flow, and the key role is determining the relationship of the interphase interaction. Many researchers have made their every effort on this subject.Drag force is regarded as the main form of interphase interaction in the traditional model of two-phase flow,it is suitable for figuring out the characteristics of gas-solid system in the dry condition.Nevertheless,with the exist of the interstitial fluid,change of characteristics will be observed in the liquid-solid system or gas-solid system with relative humidity more than 65%,which has much to do with the energy dissipation during the collision and rebound of the particles.The effect of interstitial fluid has not been took into account in the traditional model,it is necessary to make some improvements accordingly,to make the description of the characteristics of wet particle motion more sensible.This paper builds up the relationship between the coefficient of restitution and the Stokes number with the exist of interstitial fluid according to the result of experiment carried out by Gollwitzer ea al.(2012),which demonstrates with the perspective of energy dissipation during particle collision.In order to describe the process of wet particle collision more reasonablly,soft sphere model is updated with this relationship.A DEM-CFD coupled algorithm is introduced to simulate the particle motion in liquid-solid and gas-solid fluidized bed.By contrast with the result calculated by the unimproved model,the effect of interstitial fluid dring the fluidization of wet particles has been revealed.The results show that the energy disspation of collision of wet particles decreases with the increase of the Stokes number.It is more easily affected by the interstitial fluid for the particles with lower inertia.The physical properties of fluid such as density,viscousity,surface tension can also affect the effect of interstitial fluid.In liquid-solid system,the bed height of fully fluidization has a slight drop compared with the situation which not taking account of the effect of interstitial fluid.In moister gas-solid system,the particles have trend to agglomerate and move as a bulk.The cohesive effect becomes more obvious with the increase of the coating thickness.