HEAT-TRANSFER FROM IMMERSED TUBES IN A BAFFLED SLURRY BUBBLE-COLUMN

Heat transfer coefficients have been measured from heat transfer tube bundles simulating heat exchanger configurations and surrounding two-p hase and three-phase dispersions in a slurry bubble column. The tube b undles are comprised of a single tube, and five-, seven-, and thrity-s even tubes of 19 mm outer diameter. The Pyrex glass bubble column is 0 . 305 m internal diameter and 3.30 m tall and is heated electrically b y internal heaters to temperatures in the range 298 to 353 K. Air, wat er and glass beads are used as gas, liquid and solid phases respective ly. Heat transfer coefficients are measured for air-water, and air-wat er-glass bead systems as a function of air velocity up to about 0.3 m/ s, and solids concentration up to about 30 weight percent in slurries of glass beads of average diameters 125, 168 and 212 mum at temperatur es of 298, 323, 343 and 353 K. The nondimensional correlation availabl e for heat transfer coefficient is also examined and modifications in its form are proposed on the basis of experimental data. Heat transfer coefficient values are compared with the predictions based on correla tions due to Deckwer et al., Suh and Deckwer, Kim et al., and Pandit a nd Joshi. These correlations are inadequate and hence a semitheoretica l correlation is proposed which synthesizes the data successfully. The influence of tube bundle size on heat transfer coefficient is discuss ed.