HEAT TRANSFER FROM IMMERSED TUBES IN A BAFFLED SLURRY BUBBLE COLUMN

Abstract

Heat transfer coefficients have been measured from heat transfer tube bundles simulating heat exchanger configurations and surrounding two-phase and three-phase dispersions in a slurry bubble column. The tube bundles are comprised of a single tube, and five-, seven-, and thirty-seven 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 by internal heaters to temperatures in the range 298 to 353 K. Air, water and glass beads are used as gas, liquid and solid phases respectively. Heat transfer coefficients are measured for air-water, and air-water-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 μm at temperatures of 298, 323, 343 and 353 K. The nondimensional correlation available 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 correlations due to Deckwer et al., Suh and Deckwer, Kim et al., and Pandit and Joshi. These correlations are inadequate and hence a semitheoretical correlation is proposed which synthesizes the data successfully. The influence of tube bundle size on heat transfer coefficient is discussed

KEYWORDS:

• Slurry
• bubble columns
• Phase holdup
• Heat transfer coefficient
• Baffled columns