Mixing Performance of a Cross-Channel Split-and-Recombine Micro-Mixer Combined with Mixing Cell.

Makhsuda Juraeva,Dong Jin Kang

doi:10.3390/mi11070685

Abstract

A new cross-channel split-and-recombine (CC-SAR) micro-mixer was proposed, and its performance was demonstrated numerically. A numerical study was carried out over a wide range of volume flow rates from 3.1 μL/min to 826.8 μL/min. The corresponding Reynolds number ranges from 0.3 to 80. The present micro-mixer consists of four mixing units. Each mixing unit is constructed by combining one split-and-recombine (SAR) unit with a mixing cell. The mixing performance was analyzed in terms of the degree of mixing and relative mixing cost. All numerical results show that the present micro-mixer performs better than other micro-mixers based on SARs over a wide range of volume flow rate. The mixing enhancement is realized by a particular motion of vortex flow: the Dean vortex in the circular sub-channel and another vortex inside the mixing cell. The two vortex flows are generated on the different planes perpendicular to each other. They cause the two fluids to change their relative position as the fluids flow into the circular sub-channel of the SAR, eventually promoting violent mixing. High vorticity in the mixing cell elongates the flow interface between two fluids, and promotes mixing in the flow regime of molecular diffusion dominance.

Highlights

Microscale fluid mixing is an important issue in many microfluidic systems, such as micro-reactors and micro-total analysis systems
The flow regime in micro-mixers corresponds to laminar flow because of the geometric size of the mixers, and molecular diffusion becomes a major mechanism of mixing
This paper proposes a new passive micro-mixing unit combining a SAR unit with a mixing cell

Summary

Introduction

Microscale fluid mixing is an important issue in many microfluidic systems, such as micro-reactors and micro-total analysis systems (μTASs). Ansari et al [23] proposed a SAR micro-mixer based on unbalanced collision, which is caused by different flow rates in the sub-channels. Most of the SAR micro-mixers perform poorly in the range of molecular diffusion dominance To overcome this difficulty, some studies have attempted to combine different mixing techniques such as baffles, channel contraction, obstruction, etc. Numerical studies on the fluid dynamic features involved in a micro-mixer have several advantages They allow detailed visualization of the mixing process as well as the associated flow patterns such as streamlines, vortex formation, velocity vector, etc. IIff ccaallccuullaattiinngg aalloonngg tthhee cceenntteerrlliinnee ooff tthhee ssuubb--cchhaannnneell 11 aanndd tthhee mmiixxiinngg cceellll wwiitthh nnoo bbaaffflfleess,, tthhee ttoottaall lleennggtthh ooff ffllooww ppaassss ffrroomm mmoonniittoorr 11 ttoo mmoonniittoorr 22 iiss aapppprrooxxiimmaatteellyy 88005555 μμmm. Tihdits(Sdcif)fnuusimonbecroinss1ta0n4t(tihs ea rtaytpioicoafl vthaelukeinfoetricsmviaslclopsritoyteainnds itnheanmaqssudeoiffuusssionluotifoflnu. iTdh).eTShcehmReiydnt o(Sldc)snnumber is d10efi (ntehde arastRioe o=f tρhUemμkeainndhe,tiwc hveisrceoρs,itUymaenand, tdhheamndasμs diefnfuostieotnheofdefnlusiidty),. tThheemReaenynvoelldoscintyuamtbthere oisutdletf,intheed haysdrRaeul=icρdUimaeμmanedthe,r wofhmeraeinρc,hUamnenanel,,dahnadndthμe dveisncootseittyhoefdtehnesflituyi,dt,hreesmpeeacntivveellyo.city at the outlet, the hydraulic diameter of main channel, and the viscosity of the fluid, respectively

Governing Equations and Computational Procedure

Validation of the Numerical Study

Results and Discussion

Conclusions