Numerical Study On Multi-dimensional Effect Of Gas-solid Flow Field In Scaling Up Procedure In Rectangular Spouted Bed

The spouted bed are widely used in various areas such as agriculture and chemical industry as a result of its significant regular gas-solid flow.Since the 1950s,the exploration of the internal flow mechanism in spouted bed has been a hot and core issue for researchers.The scale up of spouted bed from experimental one to industrial scale is a difficult topic which puzzled the engineer and academician.Due to the complexity of effect factors on gas-solid flow property in spouted bed,as well as the experimental limitations and measurement methods,it is very difficult to explore and understand the essential mechanism of the internal flow property and scale up rule of spouted bed.With the development of computational fluid dynamics(CFD),as well as the improvement of numerical algorithms and continuous updating of computer hardware,numerical simulation turns into one of the important methods to study spouted bed.In the present work,the different scale rectangular spouted beds are investigated with the help of CFD simulation under the framework of the Euler-Euler two-fluid flow model in conjunction with kinetic theory of granular flows.The gas and solid phases are treated as continuous phase and described with the same governing equation.To save computational resources,symmetric grid was used in the simulations.This research mainly includes three parts:The first part:Five kinds of drag models and four kinds of radial distribution function models are used to study the quasi two-dimensional spouted bed from the experimental presentation of Liu.The volume fraction of particle and the axial&radial velocity distribution of particle along the bed axis for different conditions were obtained.Comparing the experimental results,optimal drag model and radial distribution function which describing the gas-solid two-phase momentum exchange and particles radial distribution probability are explored.The second part:Basing on the results of the first part,the rectangular spouted beds with 0mm(two dimensions),15mm(quasi-two-dimensional)and 100mm(three dimensions)thickness are further studied by manipulating the particle-wall specularity coefficient and restitution coefficient,.The momentum transport between the particle and the wall due to friction and collision is discussed to explore the fundamental mechanism how the micro dynamic event such as collision and friction affects the macroscopic flow field in spouted bed.The optimal parameter values are obtained by comparing experimental.The last part:Basing on the optimal boundary conditions obtained from the first and second parts,the effects of superficial gas velocity,particle-wall specularity coefficient and restitution coefficient on macroscopic flow field in spouted bed in scale up process are discussed,where the thickness of the spouted bed are stepwise increased from Omm to 100mm(thickness:0mm,15mm,30mm,50mm,75mm and 100mm)respectively.