چكيده به لاتين
Abstract:
Gas-solid fluidized-beds are practical equipment in the chemical industry due to the high rate of heat and mass transfer. One of the effective parameters on the performance of this fluidized-beds is the mixing of particles. In this study, we choose CFD-DEM simulations to study the Global (macro) and local (micro) mixing. Various injection patterns, including center oriented (CeOIP), corner oriented (CoOIP) and uniform (UIP) have been used to check the mixing quality. In order to calculate the global and local mixing, respectively, the nearest distance method and the correlation in kinetic theory of granular flows, are manipulated. By using the particles averaged moving patterns, validation of simulation results is performed. The pseudo 2-dimensional bed and the PIV-DIA method have been employed to obtain the particles averaged moving patterns. Simulation results at different air inlet velocities achieved 1.25, 1.5, 1.75 and 2 times the Umf and particle diameter of 2, 2.5 and 3 mm. In x-direction mixing, the CeOIP at 1.25 Umf, 1.75 Umf, and 2 inlet Umf velocities has the lowest time to mix, and at 1.5 Umf, the CoOIP decrease mixing time. By increasing the particle diameter from 2 to 3, UIP improves the quality of mixing. In the y-direction mixing, the CeOIP at all speeds has the lowest time to achieve mixing, and by increasing the particle diameter, the UIP had the best mixing quality. In the study of local mixing, with increasing inlet air velocity in all patterns, the averaged granular temperature, averaged diffusion coefficient, averaged bubble granular temperature, and averaged dispersion coefficient increases along the bed. At all the inflow velocities, the CeOIP has the highest averaged granular temperature and averaged diffusion coefficient and CoOIP, has the highest averaged bubble granular temperature, and averaged dispersion coefficient along the bed. In all injection patterns, the particles with the highest diameter have the highest averaged granular temperature and averaged diffusion coefficient, and particles with the lowest diameter, have the highest averaged bubble granular temperature and averaged dispersion coefficient along the bed.
Keywords: injection pattern, CFD-DEM, fluidized bed, mixing, PIV-DIA
