CFD simulation of hydrodynamics and heat transfer for scale-up of the jetting fluidized beds

Abstract

This paper presents a CFD modelling of hydrodynamics and heat transfer for scaling up the gas-solid jetting fluidized beds. Through coupling with energy conservation equation, a simple hydrodynamic model (Brandani and Zhang, 2006) is extended to predict the heat transfer between the gas and particle phases in a fluidized bed. A similitude method is established by nondimensionalizing the governing equations involved in the CFD model for fluidized beds. Numerical simulations are conducted in the platform of CFX 4.4, a commercial CFD code, together with user-defined FORTRAN subroutines. The controlling equations are verified in the fluidized bed with a pulse jet by using the penetration theory (Kuipers et al., 1992). The effect of jet on heat transfer is examined by introducing a continuous jet. The computational results show that local time-averaged heat transfer coefficient increases with an increase in solid thermal conductivity or with a decrease in jet gas velocity, particle size and nozzle size. Reasonable similarities of jet evolution, time-averaged radial voidage distribution and dimensionless heat transfer coefficient can be obtained in the standard, two-sized and five-sized fluidized beds when dimensionless parameters are matched.