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Research Papers: Micro/Nanoscale Heat Transfer

Droplet Formation and Fission in Shear-Thinning/Newtonian Multiphase System Using Bilayer Bifurcating Microchannel

[+] Author and Article Information
Yong Ren

Mem. ASME
Department of Mechanical, Materials and
Manufacturing Engineering,
Research Centre for Fluids and
Thermal Engineering,
University of Nottingham Ningbo China, 199
Taikang East Road,
Ningbo 315100, China
e-mail: yong.ren@nottingham.edu.cn

Kai Seng Koh

School of Engineering and Physical Sciences,
Heriot-Watt University Malaysia,
No. 1 Jalan Venna P5/2,
Precinct 5,
Putrajaya 62200, Malaysia
e-mail: k.koh@hw.ac.uk

Jit Kai Chin

Department of Chemical and
Environmental Engineering,
University of Nottingham Malaysia Campus,
1816, West Street, Jinjang North,
Jalan Broga,
Semenyih 43500, Selangor, Malaysia
e-mail: jit-kai.chin@nottingham.edu.my

Jing Wang

Department of Electrical and
Electronic Engineering,
University of Nottingham Ningbo China,
199 Taikang East Road,
Ningbo 315100, China
e-mail: jing.wang@nottingham.edu.cn

Conghua Wen

School of Mathematical Sciences,
University of Nottingham Ningbo China,
199 Taikang East Road,
Ningbo 315100, China
e-mail: alan.wen@nottingham.edu.cn

Yuying Yan

Research Centre for Fluids and
Thermal Engineering,
University of Nottingham Ningbo China,
199 Taikang East Road,
Ningbo 315100, China;
Research Group of Fluids and Thermal
Engineering,
Faculty of Engineering,
University of Nottingham,
Nottingham NG7 2RD, UK
e-mail: yuying.yan@nottingham.ac.uk

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received May 26, 2016; final manuscript received March 23, 2017; published online October 4, 2017. Assoc. Editor: Chun Yang.

J. Heat Transfer 140(1), 012405 (Oct 04, 2017) (7 pages) Paper No: HT-16-1310; doi: 10.1115/1.4037338 History: Received May 26, 2016; Revised March 23, 2017

With a novel platform of bilayer polydimethylsiloxane microchannel formed by bifurcating junction, we aim to investigate droplet formation and fission in a multiphase system with complex three-dimensional (3D) structure and understand the variations in mechanism associated with droplet formation and fission in the microstructure between shear-thinning/Newtonian system versus Newtonian/Newtonian system. The investigation concentrates on shear-thinning fluid because it is one of the most ubiquitous rheological properties of non-Newtonian fluids. Sodium carboxymethyl cellulose (CMC) solution and silicone oil have been used as model fluids and numerical model has been established to characterize the shear-thinning effect in formation of CMC-in-oil emulsions, as well as breakup dynamics when droplets flow through 3D bifurcating junction. The droplet volume and generation rate have been compared between two systems at the same Weber number and capillary number. Variation in droplet fission has been found between two systems, demonstrating that the shear-thinning property and confining geometric boundaries significantly affect the deformation and breakup of each mother droplet into two daughter droplets at bifurcating junction. The understanding of the droplet fission in the novel microstructure will enable more versatile control over the emulsion formation and fission when non-Newtonian fluids are involved. The model systems in the study can be further developed to investigate the mechanical property of emulsion templated particles such as drug encapsulated microcapsules when they flow through complex media structures, such as blood capillaries or the porous tissue structure, which feature with bifurcating junction.

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References

Figures

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Fig. 1

Schematic diagram of (a) bilayer microfluidic system and (b) bifurcating junction at downstream of microchannel

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Fig. 2

Generated mesh of the bilayer microsystem

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Fig. 3

Shear stress distribution at cross section located 1.05 mm upstream of bifurcating bilayer junction with mesh size of (a) 0.01 mm, (b) 0.015 mm, and (c) 0.02 mm

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Fig. 4

Comparison of shear stress results along middle line of cross section as depicted in Fig. 3 with different mesh sizes

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Fig. 5

Comparison of droplet shape at T-junction ((a)–(c)) using water/oil system at WeDP = 0.000141 and CaCP = 0.0112 and bifurcating junction ((d)–(f)) using CMC/oil system at WeDP = 0.0000353 and CaCP = 0.00562 with different grid sizes

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Fig. 6

Droplet formation ahead of bifurcating junction in Newtonian/Newtonian system versus shear-thinning/Newtonian system at the same Weber number and capillary number

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Fig. 7

Comparison of volume of generated droplets in Newtonian/Newtonian system versus shear-thinning/Newtonian system at the same Weber number and capillary number

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Fig. 8

Comparison of generation rate of droplets in Newtonian/Newtonian system versus shear-thinning/Newtonian system at the same Weber number and capillary number

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Fig. 9

Droplet fission by bifurcating junction in Newtonian/Newtonian system versus shear-thinning/Newtonian system at the same Weber number and capillary number

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