Local heat-transfer coefficient of immersed cylindrical surface in fluidized and vibrated fluidized beds

Due to the good air-particle mixing couple with the high heat and mass transfer rates, fluidized and vibrated fluidized beds of particles have been widely used for many chemical engineering processes involving particulate systems. On the other hand, in practice, for using such beds in the treatment of heat-sensitive materials (i.e., polymer, food products) the installation of heat-exchange surface within the bed are needed to provide indirect heat as well as prevent thermal degradation. Therefore, this paper presents an investigation to determine the local heat-transfer coefficient in fluidized and vibrated fluidized beds (by expressing Nu(theta) vs. Re) operated with glass ballotini particles ranging from 500 to 1100 mu m, in diameter. The data show that, at a given air velocity, the local heat-transfer coefficient obtained in the vibrated fluidized beds is significantly higher as compared to those of fluidized beds. In addition, vibrated fluidized beds can achieve higher local heat-transfer coefficients as the particle diameter is reduced from 1100 to 500 mu m and the vibration dimensionless (Gamma) is increased from 1 to 3. (C) 2011 Elsevier B.V. All rights reserved.