Centrifugal Fluidized Bed Dryer Drying Properties

In this article, drying characteristics of more than ten kinds of materials with different characters in a Centrifugal Fluidized Bed Dryer was studied. The materials studied included some vegetables and seeds, ranging from 0.99mm to 9.01mm, and the particle density varied from 873kg/m3 to 2543kg/m3, so that the particles studied had the better representatives.Firstly, the fluid dynamics performance of the Centrifugal Fluidized Bed Dryer was studied. Compared with the result in different experimental conditions, such as altering the height of the shaft, changing gas velocity or rotate speed of drum, the correlation of the minimum fluidization velocity was obtained.Secondly, on the basis of the fluid dynamics performance of CFBD, the heat transfer performance of CFBD in constant drying stage was studied carefully, and the mathematical model calculating the coefficient of heat transfer between the fluid and particles was obtained by theoretical analysis and derivation.The main factors which had great influence on the coefficient of convective heat transfer between gas and particles were presented in the paper by experiments and analysis. The paper incorporated them as fivedimensionless groups according to analysis:Through the analysis of the experimental data of 31 groups, The corresponding correlation of the constant rate drying stage was obtained :Finally, the drying curves and drying rate curves of 8 kinds of vegetables and seeds in various experimental conditions were measured and compared. The main factors which had influence on drying rate were found: the operating air velocity, the speed of rotating drum, the temperature of air flow, the shapes and characteristics of materials. Then the positive or negative influence of the above factors on drying rate was discussed.