Decompression waves in fluidized beds

G. B. Wallis, S. P. Harvey, R. Difelice

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

A packed bed of particles may be held against the permeable roof of a fluidized column by a fluid flux that is several times the minimum fluidization flux. When the fluid flux is sufficiently reduced, particles rain down and a decompression wave propagates into the packed bed. We report new data of the velocity of this wave, summarize previous work and compare with new analyses. The speed of the decompression wave cannot be predicted from continuum theories that contain a mutual drag force dependent only on the relative velocity and void fraction. Several hypotheses about additional forces are used to derive theoretical values of the decompression wave velocity which are compared with data. The three most successful hypotheses, which are shown to be roughly equivalent at the higher wave speeds, include: a force proportional to the second derivative of void fraction; a discrete averaging method over distances scaled by particle size; and a modification to the drag force using the geometrical relationship between area fraction and number density.

Original languageEnglish
Pages (from-to)839-874
Number of pages36
JournalInternational Journal of Multiphase Flow
Volume19
Issue number5
DOIs
Publication statusPublished - 1993
Externally publishedYes

Fingerprint

pressure reduction
Fluidized beds
beds
Void fraction
Packed beds
Fluxes
drag
Drag
voids
Fluids
fluids
roofs
Fluidization
rain
Roofs
Rain
Particle size
continuums
Derivatives

Keywords

  • averaging
  • constitutive equations
  • fluidization
  • stability
  • waves

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes
  • Mechanical Engineering

Cite this

Decompression waves in fluidized beds. / Wallis, G. B.; Harvey, S. P.; Difelice, R.

In: International Journal of Multiphase Flow, Vol. 19, No. 5, 1993, p. 839-874.

Research output: Contribution to journalArticle

Wallis, G. B. ; Harvey, S. P. ; Difelice, R. / Decompression waves in fluidized beds. In: International Journal of Multiphase Flow. 1993 ; Vol. 19, No. 5. pp. 839-874.
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