Local hydrodynamics and heat transfer in fluidized beds of different diameter

Heat transfer coefficients were measured in fluidization columns of 0.29 m and 1.56 m ID at fixed distance above the distributor, using an identical vertical heater, the same alumina particles and geometrically scaled bubble-cap distributors. The magnitude of the maximum heat transfer coefficients was found to be unaffected by the column diameter, but occurred at higher superficial velocities in the larger column. When the local flow structure near the heater corresponded to the turbulent flow regime of fluidization, the local heat transfer coefficients were independent of radial position in both columns.

Graphical abstractHeat transfer from an identical immersed tube to fluidized beds of the same particles was measured in columns of diameter 0.27 and 1.56 m. The results show similar maximum heat transfer coefficients occurring in both columns near the transition to turbulent fluidization, with limited radial dependence of local heat transfer.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Heat transfer from an identical immersed tube was measured in two fluidized beds. ► The same particles were fluidized in columns of diameter 0.29 m and 1.56 m. ► Maximum heat transfer coefficients were similar in both columns. ► Heat transfer coefficients reached maxima near transition to turbulent fluidization. ► Local heat transfer varied little radially in the turbulent fluidization regime.