3.3.2 Effect of Liquid Flow Rate on Bubble Size
Figure 11 conveys the variation of bubble size and quantity with liquid flow rate. The increase of liquid flow rate reduces the residence time of bubbles, resulting in a drop in quantity of bubbles. Thed av slightly changes from 330 to 340 μm at the liquid flow rate of 1-3 ml/min, and the quantity of bubbles decreased 16%. As the liquid flow rate is greater than 3 ml/min, thed av augment to 388 μm, and the quantity of bubbles decreased to 355 at 4 ml/min of liquid flow rate. With the increasement of liquid flow rate, the shear force of the liquid becomes larger, so that the drag force of the bubble during the growth process also gets larger. The unshedding bubble will coalesce with the adjacent bubble, and the bubble would start to expand. Since a growth of liquid flow rate made the bubble collision frequency and velocity ascend, the bubbles tended to coalesce, resulting in the increase of bubble size and the decrease of bubble quantity.
FIGURE 11 Effects of liquid flow rate on bubble sizes (d av) and quantity at a gas flow rate of 10 ml/min with 10 cm ceramic membrane