Figure 11. Comparison between the experimental results of DDSD
and that calculated by our previous correlation 37.
Conclusions
In this work, a method to quantitatively characterize the DIFT in PDDC
is developed based on the measurement of DBFF. We found that the DBFF
varies with column height in the PDDC under mass transfer conditions.
This variation is attributed to the interfacial tension changing caused
by mass transfer. The changing interfacial tension along the height of
the PDDC is defined as DIFT. A correlation between the DBFF and the
static interfacial tension obtained under conditions without mass
transfer in our previous work was used to determine the DIFT. The values
of DIFT along the column height were obtained by regressing the
interfacial tension in the correlation. By analyzing the equilibrium
interfacial tension and DIFT between two phases, it was found that the
difference between the DIFT and the equilibrium interfacial tension has
a positive correlation with the mass transfer flux. Moreover, it is
found that there are two types of breakage patterns, ensile breakup and
revolving breakup, under mass transfer conditions. Binary breakup plays
a dominant role in droplet breakup events at different height of the
column. Under mass transfer conditions, the DDSD is inverted U-shaped at
different heights. To introduce a single parameter of DIFT is sufficient
to describe the droplet breakage under mass transfer conditions in the
PDDC, no other parameters are needed.
Acknowledgments
We gratefully acknowledge the support of the National Natural Science
Foundation of China (21776151, 21576147, 21376132).
Notation