FIGURE 6 Images of microbubbles formed at different pressures:
(A) 0.2 MPa, (B) 0.3 MPa, (C) 0.4 MPa, (D) 0.5 MPa and (E) 0.6 MPa.
Liquid flow rate: 1.0 ml/min and gas flow rate: 10 ml/min with 10 cm
ceramic membrane
FIGURE 7 Effect of gas pressure on the average bubble diameter.
Liquid flow rate: 1.0 ml/min and gas flow rate: 10 ml/min with 10 cm
ceramic membrane
3.2 Flow Pattern
The flow patterns of gas-liquid in ceramic membranes mainly include
bubble flow and slug flow, as shown in Figure 8. It can be seen
that the shape of the bubble is closely related to the gas flow and
liquid flow. Therefore, a prediction model based on the critical point
bubble for flow pattern is proposed as Eq. (4):
\begin{equation}
\left\{\begin{matrix}Q_{G}=45-26Q_{L}\text{\ \ \ }\left(0<Q_{L}\ <1,0<Q_{G}<20\right)\text{\ \ \ }R^{2}=0.94857\ \ \ \ \ \mathbf{\text{bubble\ flow}}\\
Q_{G}=16.5+2.5Q_{L}\text{\ \ \ \ \ }\left(Q_{L}\ \geq 1,\ Q_{G}\geq 20\right)\text{\ \ \ \ \ \ \ \ \ \ \ \ \ }R^{2}=0.85714\ \ \ \ \ \mathbf{\text{slug\ flow}}\text{\ \ \ \ \ }\\
\end{matrix}\right.\ (4)\nonumber \\
\end{equation}When the liquid flow and gas flow are low, the gas phase is
discontinuously distributed in the form of small bubbles in the liquid
phase. The bubbles are spherical but the gas holdup is low, and the flow
pattern at this time is mainly sparse bubble flow (Figure 9A). With the
increase of gas flow, more small bubbles are generated and transferred
to bubble flow (Figure 9B). As the gas flow rate continues to increase,
the small bubbles gather and transform into large bubbles, which take on
the shape of a convex front and a flat back, with the flow pattern
transforming into the slug flow in Figure 9C. It has been found large
bubbles have a small phase interfacial area, which is not conducive to
mass transfer.28
FIGURE 8 Flow patterns with ceramic membrane of two phases.
Liquid flow rate: 1.0 ml/min and gas flow rate: 10 ml/min with 10 cm
ceramic membrane