The Influence of Continuous Phase Velocity on Bubble Size

The Influence of Continuous Phase Velocity on Bubble Size 

Depending on its subtraction from or addition to the buoyancy force, the continuous phase velocity can either increase or decrease the bubble volume. Normally, this velocity is such that the bubble detaches prematurely from the nozzle tip. Maier (M2) has shown that the shear force experienced by the bubble, which causes its premature detachment, is a maximum when the continuous phase flows at right angles to the nozzle axis. 

Krishnamurthy et ah (K13) have confirmed the above conclusion and have developed an expression for evaluating the bubble volume under conditions of flow when the corresponding volume for static conditions is given. These authors used capillaries of different diameters ground at the tip as nozzles. The capillaries were arranged horizontally, and the fluid travelled vertically so as to add to the buoyancy. The liquid viscosity was varied from 1 to 30 cp and the surface tension from 62 to 70 dyn/cm. 

The results showed that for all nozzle diameters the decrease in bubble volume with an increase in the continuous phase velocity is nonlinear. Further, for any particular velocity, the reduction in the bubble volume is greater as the liquid viscosity is increased. 

The reduction in bubble volume due to the continuous phase velocity is attributed to an extra upward drag force, which adds to the buoyancy. Thus, 

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X. The Influence of Continuous Phase Velocity on Bubble Size. 332... 

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