Heat transfer between a vertical tube and an air fluidized bed at moderate temperatures (335–528 K)

Abstract

Heat transfer coefficient is measured between a 25.4 mm outer diameter smooth vertical tube immersed in 0.254 m internal diameter fluidized beds of sand (d_p = 265, 507 and 787 μm), glass beds (239, 357 and 412 μm), silicon (368 μm) and alumina (267 μm) as a function of bed temperature (335 – 528 K) and fluidizing velocity. The solids movement and mixing in the bed is investigated by measuring the heat transfer coefficient at two radial positions in the bed for various values of fluidization velocity and bed temperature. The minimum fluidization velocity, bed voidage and maximum heat transfer coefficient are also reported for different experimental conditions. The qualitative variation of h_o with different operating and system parameters is found consistent with the known mechanisms of heat transfer for an immersed surface in a fluidized bed. Quantitative correlation of h_o and h_omax will be reported in a future publication.