Determination of Mass Transfer Coefficient in Fluidized Bed Dryer with Bed and Particle Diffusion Coefficient

High mass transfer rate in fluidized bed dryer causes drying of moist particles in short residence time and obtaining homogeneity of their moisture content. It is difficult to define an exact mass transfer coefficient for drying of solids because of fluidized state and bubble moving. A method for determination of mass transfer coefficient of single spherical particle in fluidized bed is combination of mass transfer coefficients of bed and particles.In this paper, the basic principles of these two mechanisms, mass transfer in bed and particles, were illustrated and many correlations which can predict overall mass transfer coefficient with aid of the mechanisms, were presented. These correlations were derived by different researchers for different conditions and particles. With studying of different correlations and application of regression method and error function, the equations which can estimate Sherwood number in different flow regimes and for different particles, has been presented. The error values and percentages show that the obtained results from this general equation is adequately comparable with previous data of mass transfer coefficient of particles in fluidized bed.