Research Papers: Fundamental Issues and Canonical Flows

Analysis of a Novel Y-Y Micromixer for Mixing at a Wide Range of Reynolds Numbers

[+] Author and Article Information
Vladimir Viktorov

Department of Mechanical and Aerospace
Engineering (DIMEAS),
Politecnico di Torino,
Turin 10129, Italy
e-mail: vladimir.viktorov@polito.it

Carmen Visconte

Department of Mechanical and Aerospace
Engineering (DIMEAS),
Politecnico di Torino,
Turin 10129, Italy
e-mail: carmen.visconte@polito.it

Md Readul Mahmud

Department of Mechanical and Aerospace
Engineering (DIMEAS),
Politecnico di Torino,
Turin 10129, Italy
e-mail: md.mahmud@polito.it

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 14, 2015; final manuscript received March 5, 2016; published online May 20, 2016. Assoc. Editor: Moran Wang.

J. Fluids Eng 138(9), 091201 (May 20, 2016) (9 pages) Paper No: FE-15-1483; doi: 10.1115/1.4033113 History: Received July 14, 2015; Revised March 05, 2016

A novel passive micromixer, denoted as the Y-Y mixer, based on split-and-recombine (SAR) principle is proposed and studied both experimentally and numerically over Reynolds numbers ranging from 1 to 100. Two species are supplied to a prototype via a Y inlet, and flow through four identical elements repeated in series; the width of the mixing channel varies from 0.4 to 0.6 mm, while depth is 0.4 mm. An image analysis technique was used to evaluate mixture homogeneity at four target areas along the mixer. Numerical simulations were found to be a useful support for observing the complex three-dimensional flow inside the channels. Comparison with a known mixer, the tear-drop one, based on the same SAR principle, was also performed, to have a point of reference for evaluating performances. A good agreement was found between numerical and experimental results. Over the examined range of Reynolds numbers Re, the Y-Y micromixer showed at its exit an almost flat mixing characteristic, with a mixing efficiency higher than 0.9; conversely, the tear-drop mixer showed a relevant decrease of efficiency at the midrange. The good performance of the Y-Y micromixer is due to the three-dimensional 90 deg change of direction that occurs in its channel geometry, which causes a fluid swirling already at the midrange of Reynolds numbers. Consequently, the fluid path is lengthened and the interfacial area of species is increased, compensating for the residence time reduction.

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Fig. 1

Structure of the micromixers: (a) Y-Y and (b) tear-drop

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Fig. 3

Prototype of the Y-Y micromixer: (a) before assembling and (b) after filling with fluids at Re = 1

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Fig. 4

Example of calibration curve showing the relationship between the mass fraction of blue dye and the image's gray intensity

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Fig. 5

Grid dependency of the Y-Y mixer: efficiency along the mixer

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Fig. 6

Fluid path lines at Re = 1: (a) top view and (b) side view of elements 1 and 2

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Fig. 7

Path lines at the mixer exit: (a) Re = 1, (b) Re = 50, and (c) Re = 100

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Fig. 8

Mixing efficiency along the Y-Y mixer at Re = 1

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Fig. 9

Numerical and experimental mixing efficiency at the exit of the Y-Y and of the tear-drop mixers, varying Reynolds numbers

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Fig. 10

Numerical and experimental pressure drop within the Y-Y and the tear-drop micromixers

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Fig. 11

Concentration distribution at channel cross section and path lines within the Y-Y micromixer, varying Reynolds numbers: (a) and (b) Re = 1, (c) and (d) Re = 20, (e) and (f) Re = 100

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Fig. 12

Path line distributions in the tear-drop micromixer, varying Reynolds numbers: (a) Re = 1, (b) Re = 20, and (c) Re = 100

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Fig. 13

Velocity vectors highlighting secondary flow at the rectangular channel just at the inlet of the first element of the two micromixers, varying Reynolds numbers: (a) Y-Y and (b) tear-drop




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