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Transient heating and cooling of cocurrent three‐phase fluidized beds
Author(s) -
Grandjean B. P. A.,
Carreau P. J.,
Paris J.
Publication year - 1991
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450690316
Subject(s) - sparging , materials science , fluidized bed , thermodynamics , particle (ecology) , dispersion (optics) , heat transfer coefficient , heat transfer , mechanics , chemistry , optics , geology , physics , oceanography
The thermal transient behaviour of three‐phase fluidized beds have been investigated for a liquid viscosity ranging from 35 to 75 mPa · s. For the operating conditions used in this study, a 6 mm glass particle bed was found to have a thermal response similar to that of a fixed bed. The transient responses, which were not significantly affected by gas sparging, were, however, faster for heating than for cooling. This result has been analyzed from a model assuming liquid plug flow through stationary particles using combined free and forced convection correlations for heat transfer around the particles. Different correlations are then proposed to predict the contribution of natural convection to the liquid‐to‐particle heat transfer in heating and cooling modes. The effect of gas sparging was found to strongly affect The 2.0 mm particle bed responses but only moderately the 3.9 mm bed responses. These responses were analyzed using axial dispersion models for the liquid and solid phases. For the 3.9 mm particle bed, the axial dispersion coefficient of the solids, E ZS , was found to be of the same order of magnitude as that of the liquid coefficient, E ZL . However, the value of E zs for the 2 mm particle bed was found to be five times that of E ZL .