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 Nuθ vs. Re) operated with glass ballotini particles ranging from 500 to 1100 μm, 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 μm and the vibration dimensionless (Γ) is increased from 1 to 3.

► Local heat-transfer coefficient in fluidized and vibrated fluidized beds was investigated. ► Vibrated fluidized beds performance on heat transfer is higher than those of fluidized beds. ► Increasing vibration leads to the increase of the local heat-transfer coefficient in the beds. ► Decreasing particle size will increase the local heat-transfer coefficient in the beds.