(7e) Effect of Scale-up on the Heat Transfer Coefficient and Rate In Bubble Columns

Scale-up effects on the time-averaged local heat transfer coefficients were investigated in two different size columns with diameters of 0.16 and 0.44 m. Air-water system was used with superficial gas velocities ranging from 0.03 to 0.30 m/s which cover both the homogenous and heterogeneous flow regimes. By using an advanced fast response heat transfer probe, the local instantaneous heat transfer coefficients were measured in fully developed flow region (Z/D=5.5) at different radial positions of the columns. These measurements are important to select proper location and appropriate configuration of internal heat exchanging surfaces in bubble columns. Experiments results indicate that time-averaged local heat transfer coefficients in 0.44 m column diameter are larger than these obtained in 0.16 m column diameter. The heat transfer coefficients in the center of both columns for all the conditions studied are larger than those near the wall region. Also, local heat transfer coefficient increases as superficial gas velocity increased.

Keywords: bubble column; heat transfer coefficients; column diameter effect; scale-up.

Note: the work was performed at Washington University in St. Louis.