CFD Simulation Of Fluid Flow Characteristics In Spherical Particles Packed Bed

Particle packed bed has been applied widely in many fields,such as chemical engineering,metallurgical engineering,agriculture and so on.The research on fluid dynamics characteristics of packed bed can provide solutions for problems of packed bed in use,and provide theoretical basis for the designing and manufacturing of packed bed equipment.The single-phase flow in spherical particle packed bed were simulated by using computational fluid dynamics software FLUENT,and main works and conclusions were as follows:First,the two-dimensional physical model of spherical particle packed bed was established,and fluid flow was simulated.The influence of interparticle void size,inlet velocity and particle packing method on flow characteristics were analyzed.According to the simulation results,pressure decreased by degrees in the axial direction.Pressure drop,flow velocity and eddy current were inversely proportional to the size of interparticle void.Pressure drop and outlet velocity were proportional to inlet velocity.Flow velocity near wall were bigger under triangle arrangement of particles,and compared with quadrilateral arrangement,triangle arrangement can make fluid flow more effective and more stable,thus weaken eddy diffusion,but higher pressure drop.Secondly,the two-dimensional physical models of spherical particle packed bed with diameter-expansion zone and diameter-reduction zone were simulated and analyzed respectively.Pressure distribution in two packed bed above mentioned were same as packed bed with normal column.But pressure drop increased because of existence of diameter-variation zones,pressure drop of packed bed with diameter-expansion zone increased by about 10%,and pressure drop of packed bed with diameter-reduction zone increased by over 10%.Flow velocity and eddy current weakened in diameter-expansion zone and enhanced in diameter-reduction zone.With the increase of diameter of diameter-expansion zone,the pressure drop increased first and then decreased,and with the increase of diameter of diameter-reduction zone,it increased all the time.At the end,the three-dimensional physical models of several spherical particle packed bed at 1<D/d<3 were simulated and analyzed.Porosity was proportional to D/d at D/d<2,while porosity was influenced by packing method at D/d=2.3,and the sequence of the corresponding porosity of the three packing methods is(C)>(A)>(B).Pressure and flow velocity in main flow channel composed of wide voids between particles and wall were bigger,and eddy current was weaker,while in interparticle void and narrow void between particles and wall,pressure and flow velocity were smaller and eddy current was more violent.The deviation between pressure drop of packed bed at 1<D/d<3 and Ergun equation was very large,and pressure drop of packed bed at 1<D/d<3 can not be predicted by Ergun equation precisely.According to the simulation results,modified pressure drop equation was proposed.