Survey of heat transfer mechanisms in a slurry bubble column

Heat transfer mechanisms in the bulk and distributor regions of a slurry bubble column are investigated based on the measurements of local heat transfer in a 0.28 m diameter Plexiglas column. The gas, liquid and solid phases used are oil-free compressed air, tap water and 35 μm glass beads. The slurry concentration and superficial gas velocity are varied from 0 to 40 vol% and 0.05 to 0.30 m/s respectively. Measurements have been made with a fast response heat flux probe which provided local instantaneous heat transfer coefficients. The time-averaged heat transfer coefficients in the bulk region were on average about 50% higher than the distributor region of the column. The wall region heat transfer coefficients are well predicted by the correlation of Deckwer et al. (1980). Heat transfer mechanism in column centre can be adequately described by the consecutive film and surface renewal model. Les mecanismes de transfert de chaleur dans le coeur et dans la region du distributeur d'une colonne a bulles a suspensions sont etudies en mesurant le transfert de chaleur local dans une colonne en plexiglass de 0.28 m. Les phases gazeuse, liquide et solide utilisees sont de l'air cornprime dehuile, de l'eau du robinet et des billes de verre de 35 μm. On a fait varier la concentration des suspensions et la vitesse de gaz superficielle de 0 a 40% en volume et de 0.05 a 0.30 m/s, respectivement. Les mesures ont ete faites a l'aide d'une sonde de flux de chaleur a reponse rapide qui fournit les coefficients de transfert de chaleur instantanes locaux. Les coefficients de transfert de chaleur moyennes dans le temps dans le coeur etaient, en rnoyenne, environ 50% superieurs a ceux de la region du distributeur dans la colonne. Les coefficients de transfert de chaleur de la region de la paroi sont bien predits par la cordation de Deckwer et al. (1980). Le mecanisme de transfert de chaleur au centre de la colonne peut ětre adequatement decrit par le modele de renouvellement de surface et de film consecutif.

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