HEAT TRANSFER AND HYDRODYNAMIC INVESTIGATIONS IN A BAFFLED BUBBLE COLUMN: AIR-WATER-GLASS BEAD SYSTEM

Abstract

Measurements of heat transfer coefficient between an immersed surface and surrounding two- and three-phase dispersions have been conducted as a function of gas velocity in a cylindrical bubble column equipped with either a single axial tube or a seven-tube bundle at 309 K. Gas holdup is also measured under the same conditions. In particular, the systems that have been investigated are air-water and air-water-glass beads. For the latter system, glass beads of three different sizes (50-143 μm) have been used and slurry concentration has been varied up to thirty percent by weight. It is observed that the seven-tube bundle configuration leads to higher heat transfer coefficient and gas holdup values over the entire air velocity range than the single axial tube arrangement. The influence of particle size and slurry concentration is nominal at least as long as it is less than ten weight percent. The presence of solids in the column lowers the gas holdup and raises the heat transfer coefficient. These qualitative variations have been discussed in terms of the bubble dynamics, and liquid or slurry movement in the bubble column that prevails as discrete bubbling, bubble coalescing and coalesced bubble regimes are encountered by increasing the air velocity. Gas holdup and heat transfer coefficient data have been correlated