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