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Measurement of internal flow field during droplet formation process accompanied with mass transfer

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Abstract

The internal flow field during droplet formation stage accompanied with mass transfer is heuristically investigated in a T-junction micro-channel. De-ionized water/phosphate acid/butanol is used as the working system. Micro-PIV measurement is conducted to capture the velocity distribution inside the droplet. Experimental results illustrate that as the mass transfer is involved in this process, the dispersion size of droplet is decreased. There exists an internal circulation inside the droplet during formation stage in the T-shape micro-channel. The velocity of vortex inside the droplet can be reduced when the mass transfer process is enhanced. A parameter of swirling strength is applied to demonstrate the convection effect inside the droplet. At the initial stage of the formation process, swirling strength of the vortices is increased as the phosphate acid concentration increases. But, as the generation of droplet, the swirling strength of the condition with lower phosphate acid concentration increases much faster than that with higher phosphate acid concentration. The experiment results can help to explore the mass transfer mechanism in micro-devices.

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Abbreviations

d e :

Effective diameter of seeding particles on CCD (µm)

d p :

Diameter of seeding particles (µm)

d s :

Point spread function (µm)

M :

Magnification of the lens

NA:

Numerical aperture (dimensionless)

FOV:

The resolution of the CCD (m)

n :

The number of pixels per interrogation region (pixel)

RES:

The field of view in the flow direction (pixel)

Δt :

Time interval (s)

T :

Generation time of the droplet in a whole period (s)

U max :

Maximum velocity in the flow direction (m/s)

λ :

Swirling strength (dimensionless)

ɛ :

Generation extent of a droplet (dimensionless)

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Acknowledgment

Financial supports from National Natural Science Foundation of China (21406129, 91334201, U1463208, U1302271) and China Postdoctoral Science Foundation (2014M550741) are gratefully acknowledged.

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    Authors and Affiliations

    1. The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, China

      Xi Wang, Guotao Liu, Kai Wang & Guangsheng Luo

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    1. Xi Wang
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    2. Guotao Liu
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    3. Kai Wang
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    4. Guangsheng Luo
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    Corresponding author

    Correspondence to Guangsheng Luo.

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    Xi Wang and Guotao Liu have contributed equally to this work.

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    Wang, X., Liu, G., Wang, K. et al. Measurement of internal flow field during droplet formation process accompanied with mass transfer. Microfluid Nanofluid 19, 757–766 (2015). https://doi.org/10.1007/s10404-015-1600-6

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    • DOI: https://doi.org/10.1007/s10404-015-1600-6

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