Abstract
In the present work, the effect of the restitution coefficient on the numerical results for a binary mixture system of sand particles and char particles in a bubbling fluidized bed with a huge difference between the particles in terms of density and volume fraction has been studied based on two-fluid model along with the kinetic theory of granular flow. Results show that the effect of restitution coefficient on the flow characteristics varies in different regions of the bed, which is more evident for the top region of the bed. The restitution coefficient can be categorized into two classes. The restitution coefficients of 0.7 and 0.8 can be included into one class, whereas the restitution coefficient of 0.9 and 0.95 can be included into another class. Moreover, four vortices can be found in the time-averaged flow pattern distribution, which is very different from the result obtained for the binary system with the similar values between particles in density and volume fraction.
Highlights
Bubbling fluidized beds are commonly used in industrial processes [1], such as combustion and gasification, due to their good mixing ability and heat transfer characteristic between the gas and solid phases
For the binary particles the experimental system huge difference in density volume fraction between particles, the predicted degree betweenwith particles, the predicted degreeand of segregation compared with experimental result may be between particles, the predicted degree of segregation compared with resultvalue may be of experimental result may be too low, whenexperimental a From relatively small of toosegregation low, when compared a relativelywith small value of restitution coefficient is adopted
The effect of the restitution coefficient on the numerical results for a binary particles system in a bubbling fluidized bed with the huge difference between the particles in terms of density and volume fraction has been studied based on two-fluid model along with the kinetic theory of granular flow
Summary
Bubbling fluidized beds are commonly used in industrial processes [1], such as combustion and gasification, due to their good mixing ability and heat transfer characteristic between the gas and solid phases. The particle collision characteristics are defined based on the restitution coefficient, and the wall boundary conditions are defined in at least three ways, which are the traditional no-slip boundary conditions and two partial slip conditions [9,10] The effects of these parameters on the simulation results have been studied by some researchers. In this study, based on a Gidaspow drag model and no-slip wall boundary conditions, a simulation is carried out to investigate the effect of the restitution coefficient on the segregation and flow characteristics of a binary particles system in a bubbling fluidized bed with a huge difference between the particles in terms of density and volume fraction. According to the comparison of results between computation and experiment, a suitable scope of the restitution coefficient is determined, and the effect of different particles characteristics in the binary mixture on the fluid dynamic behavior is compared
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