A model of heat transfer in gas fluidized beds

Numerical calculation of wall‐to‐bed heat‐transfer coefficients in gas‐fluidized beds

“…However, at relatively short packet residence times the effect of this surface layer becomes increasingly important and the simple emulsion phase model fails. Therefore, this model type has been refined by several workers (Baskakov, 1969; Kubie and Broughton, 1975) to extend its validity to relatively short packet residence times.…”

“…Kubie and Broughton (1975) modified the simple packet renewal theory to allow for property variations near the heat-transfer surface. They used simple geometrical considerations to model the spatial voidage variation normal to the heat-transfer surface and subsequently used the resulting expression for the voidage profile to describe the corresponding property variations.…”

Wall-to-bed heat transfer in a circulating fluidized bed for the reduction of iron ore particles

“…[6,[12][13][14][15][16] However, recent experiments revealed a linear variation of voidage along the radial direction from the surface to the core-annulus interface. [20,23] Hence, it is assumed in Eq.…”

“…In this work, a free-slip condition was applied for the wall boundary, and a linearity for radial variation of the voidage in the annulus region; other research groups assumed a constant voidage in the annulus region. [6,[12][13][14][15][16] Model predictions were compared with experimental results taken from the literature and showed good agreements. The overall heat-transfer phenomenon in the CFB reactor of iron ore particles also has been discussed.…”

“…To resolve such a problem, this model has been modified by introducing the concept of a time-independent contact resistance to account for the spatial voidage variation near the heat-transfer surface. [13,14] In spite of modifications, the refined emulsion-phase model has limited use due to the lack of actual packet residence times that cannot easily be obtained by measurements.…”