AICHE JOURNAL
·
2021
·Vol. 67
·期 5
·e17165
·
IF 3.993
Xin Huang,Limin He,Xiaoming Luo,Ke Xu,Yuling Lü,Donghai Yang
The dynamic behaviors of two droplets and droplet cluster under an alternating current (AC) electric field are investigated. Two droplets generally undergo transformation from complete coalescence to partial coalescence and finally to non-coalescence as the electric capillary number Ca p increases. The critical electric capillary number Ca pc for complete coalescence in the AC electric field remains unchanged and is twice as large as that in the direct current (DC) electric field when the frequency f ≥ 250 Hz. Charge transfer and reversal of electric field result in the reversal of the direction of electric force, which is the fundamental mechanism of non-coalescence of two droplets and chain formation in droplet cluster. The number of rebounds dramatically increases as f increases, promoting the stability of droplet chain. The droplet chains in the high-frequency AC electric field are longer and more stable than those in the low-frequency AC electric field.
研究领域:
流体力学
·
电动力学
✓ 已验证
产品关联
DOI
高影响因子
LANGMUIR
·
2020
·
IF 3.557
Xin Huang,Limin He,Xiaoming Luo,Ke Xu,Yuling Lü,Donghai Yang
Electrocoalescence technology is an important method for the demulsification of crude oil emulsion, but its development is restricted by the short circuit caused by droplet chain formation. To reveal the formation mechanism of droplet chains, the electrocoalescence behaviors of two droplets and droplet clusters under pulsed direct current (DC) electric fields are experimentally studied. The two droplets usually successively undergo complete coalescence, partial coalescence, and noncoalescence as the electric field strength increases. The critical electric field strengths for complete coalescence under pulsed DC electric fields with different frequencies are obtained. The effects of the electric field waveform and frequency on the noncoalescence characteristics of two droplets and the stability of droplet chains are explored. The droplet chains under a high-frequency electric field are more stable and longer than those under a low-frequency electric field due to the reduction of the movement distance and the generation of daughter droplets from tip streaming. The reversal of the composition of electric forces due to charge transfer is the fundamental mechanism of noncoalescence of two droplets and chain formation in the emulsion under a pulsed DC electric field.
研究领域:
物理学
·
化学工程
✓ 已验证
DOI
PubMed
高影响因子
PHYSICS OF FLUIDS
·
2015
·Vol. 27
·期 8
·
IF 2.031
Liu Zhou,Wyss Hans M.,Fernandez-Nieves Alberto,Shum Ho Cheung
We study the dynamics of two pinned droplets under the influence of an applied electric stress. We find that at a sufficiently strong field, this stress is sufficient to induce contact of the droplets. Interestingly, upon such contact, the dynamic behavior sensitively depends on the separation distance between the droplets. Besides the classical “coalescence” regime, we identify two other dynamic regimes: “fuse-and-split” and “periodic non-coalescence.” In the “fuse-and-split” regime, the droplets first fuse to form a jet, which subsequently breaks up into two droplets. In the “periodic non-coalescence” regime, the droplets contact and bounce away periodically without coalescence. Further analysis indicates that while the electric stress stretches the droplets into shapes that depend on the initial droplet separation, the surface tension stress dominates over the electric stress as soon as the droplets touch. We show that the shapes of the contacting droplets determine their subsequent dynamics. Our work provides a rationale for understanding the interplay between surface tension and electric stresses that govern the behavior of charged droplets and could inspire new methods for characterizing emulsion stability and surfactant performance.
研究领域:
物理学
·
材料科学
·
界面化学
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2024
·Vol. 70
·期 8
·e18462
·
IF 3.5
Xin Huang,Mindan Chen,Yunyun Huang,Xiaoming Luo,Lin Teng,Longqiang Xiao,Jiaqing Li
Excessive electric field strength causes the droplets to contact but not coalesce, severely deteriorating the oil–water separation efficiency. The investigation of the non-coalescence of nonidentical droplets in oil under a DC electric field is conducted using high-speed photography. The effects of droplet volume ratio and interfacial tension ratio on the characteristics and critical parameters for droplet non-coalescence are systematically explored. The results show the critical electrocapillary number for the non-coalescence of nonidentical droplets and critical contact cone angle decreases as the volume sum increases or the interfacial tension ratio decreases, which is related to the competition between the resultant electric field force and the interfacial tension force. These results contribute to optimizing the operating parameters of the electric coalescer and improving the oil–water separation efficiency.
研究领域:
化学工程
·
流体力学
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2022
·Vol. 69
·期 4
·e17975
·
IF 4.167
Xin Huang,Yijia Lu,Wanrui Li,Xiaoming Luo,Weidong Li,Jiaqing Li,Pengbo Yin,Lin Teng
The droplet non-coalescence characteristics and mechanism under a DC electric field are investigated by comprehensively using high-speed microscopic experiments, molecular dynamics simulations, and interface dynamics simulations. The researches show whether two droplets coalesce or not depends on the evolution of liquid bridge. The liquid bridge evolution is not only dominated by the electric force F E and the capillary force F i , but also slowed down by the viscous force. The relative strength of F E and capillary force F i relies on the electric capillary number Ca and the maximum liquid bridge radius R * max . The droplet non-coalescence is more likely to happen as the Ca increases or the R * max decreases. Furthermore, the critical value Ca c for droplet non-coalescence reduces as the R * max decreases. The ion transportation causes uneven distribution of ions and thus strengthens the F E , resulting in the non-coalescence. These results provide significant guidance for efficient demulsification of water-in-oil emulsion.
研究领域:
物理学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
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