Enhancement of mixing performance of single-screw extrusion processes via chaotic flows: Part II. numerical study

Kim, S. J.; Kwon, Tai Hun

doi:10.1002/(sici)1098-2329(199621)15:1<55::aid-adv5>3.0.co;2-j

Cited by 34 publications

(12 citation statements)

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“…It should be noted that there is an adverse effect of the barrier on the flow rate. According to the previous reports on the chaos screw [15,16], the flow rate with the inserted barrier structures might be decreased by about 10% from the flow rate of SGM under the same pressure drop. But at the cost of such a small reduction in flow rate, much higher mixing efficiency could be achieved by the existence of barriers [15].…”

Section: N N=1mentioning

confidence: 87%

“…In view of mixing efficiency, the existence of a hyperbolic point in the velocity field of co-rotating cross-sectional flows leads to efficient chaotic mixing passively, by inducing exponential interfacial area growth at even low Re (Re < 1) [13,15,16]. Figure 1 shows the first practical example of chaotic mixing in the polymer extrusion process by means of the so-called 'chaos screw', which was proposed by Kim and Kwon [15]. The size of the screw in the polymer extrusion process is usually macroscale, i.e., in the order of 10 0 -10 3 mm.…”

Section: Introductionmentioning

confidence: 99%

“…The channel for the molten polymer is created by the screw root, two adjacent flights and a barrel wall. In [15], the channel width (which is the distance between two flights of the screw) and height (the height of flight) were 16.6 mm and 3.5 mm, respectively. However, the viscosity of molten polymer is usually of the order of 10 3 Pa s which is about 10 6 times higher than that of water so that Re 1.…”

Section: Introductionmentioning

confidence: 99%

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A barrier embedded chaotic micromixer

Kim

Lee

Kwon

et al. 2004

J. Micromech. Microeng.

214

107

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Mixing enhancement has drawn a great attention to designing of micromixers, since the flow in a microchannel is usually characterized by a low Reynolds number (Re) which makes mixing quite a difficult task to complete. In this regard, we present a new chaotic passive micromixer, called a barrier embedded micromixer (BEM). In the BEM, chaotic flow is induced by periodic perturbation of the velocity field due to periodically inserted barriers along the top surface of the channel while a helical type of flow is obtained by slanted grooves on the bottom surface in the pressure driven flow. A T-channel and a microchannel with only slanted grooves were fabricated for the purpose of experimental comparison. Mixing performance has been experimentally characterized in two ways: (i) change of average mixing intensity by means of phenolphthalein and (ii) mixing patterns via a confocal microscope. Experimental results showed that BEM has better mixing performance than the other two. A characteristic required mixing length, defined in view of intensity change, increases logarithmically with Re in BEM. The confocal microscope images indicated that BEM could achieve almost complete mixing. The chaotic mixing mechanism, proposed in this study can be easily applied to integrated microfluidic systems, such as micro-total-analysis-systems, lab-on-a-chip and so on.

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Section: N N=1mentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A barrier embedded chaotic micromixer

Kim

Lee

Kwon

et al. 2004

J. Micromech. Microeng.

214

107

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“…Stroock et al (2002) obtained helical flow using oblique ridges on the floor of the microchannel, and designed chaotic micromixer referred to as the staggered herringbone mixer by patterning grooves on the floor of the microchannel. In addition, geometrical perturbations in a periodic manner on the flow field can induce stretching and folding of the material elements, resulting in chaotic mixing (Ottino 1989;Kim and Kwon 1996;Hwang and Kwon 2000;Kim et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Improved serpentine laminating micromixer with enhanced local advection

Park

Kim

Kang

et al. 2007

Microfluid Nanofluid

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It is a complicated task to achieve high level of mixing inside a microchannel because the flow is characterized by low Reynolds number (Re). Recently, the serpentine laminating micromixer (SLM) was reported to achieve efficient chaotic mixing by introducing ''F''-shape mixing units successively in two layers such that two mixing mechanisms, namely splitting/recombination and chaotic advection, enhance the mixing performance in combination. The present paper proposes an improved serpentine laminating micromixer (ISLM) with a novel redesign of the ''F''-shape mixing unit: reduced crosssectional area at the recombination region locally enhances advection effect which helps better vertical lamination, resulting in improved mixing performance. Flow characteristics and mixing performances of SLM and ISLM are investigated numerically and verified experimentally. Numerical analysis system is developed based on a finite element method and a colored particle tracking method, while mixing entropy is adopted as a mixing measure. Numerical analysis result confirms enhanced vertical lamination performance and consequently improved mixing performance of ISLM. SLM and ISLM were fabricated by polydimethylsiloxane (PDMS) casting against SU-8 patterned masters. Mixing performance is observed by normalized purple color intensity change of phenolphthalein along the downchannel. Flow characteristics of SLM and ISLM are investigated by tracing the purple interface of two streams via optical micrograph. The normalized mixing intensity behavior confirms improved mixing performance of ISLM, which is consistent with numerical analysis result.

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“…Chaotic mixing was produced in various mixers with different geometries, whereby the length and the area of the fluid elements increased exponentially with time as opposed to linear growth under steady shear flow conditions. Eccentric cylinder systems [70,71], rectangular cavity [72], two rotating rods in tanks [73], stirred tanks [74], static mixers [75][76][77], and chaotic single-screw extruders [78][79][80][81] are among the examples of mixers with chaotic flows. The effectiveness of chaotic mixers in processing of polymer blends and polymer nanocomposites has also been demonstrated [81][82][83][84][85][86][87][88][89].…”

Section: Chaotic Mixingmentioning

confidence: 99%

Evolution of Nonlinear Rheology and Network Formation during Thermoplastic Polyurethane Polymerization and Its Relationship to Reaction Kinetics, Phase Separation, and Mixing

Jana

2010

Nonlinear Dynamics With Polymers

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Understanding the evolution of nonlinear rheological properties during polymerization has been of significant industrial and academic interest [1]. The industrial interest originated from the design, operation, and control requirements of polymerization processes [2,3]. The industrial polymerization processes cover a broad spectrum from bulk production of thermoplastics, such as polyolefins, to production of thermosets, such as tires, comprising many simultaneous steps, such as chemical reactions and mixing, followed by compounding, molding, and cross-linking reactions [4,5]. The most relevant and widely documented rheological property for success of industrial processes is the viscosity of the polymerizing medium, which directly influences mass, heat, and momentum transfer processes. The academic interest, on the other hand, has its roots in utilizing rheology as a valuable tool to understand the properties of polymer chains whether in bulk, in solution, or in a polymerizing medium [6]. Monitoring the changes in rheological properties, such as normal stresses, relaxation times, storage, and loss moduli, which are usually nonlinear functions of time, temperature, and morphology, has undeniable significance in providing insights into structure and properties of polymers as they develop during polymerization or during shape-forming operations such as of extrusion, injection molding, casting, and film blowing, to name a few.The nonlinear rheological properties of growing polymer chains, irrespective of the growth mechanisms -such as free-radical or step-growth -are governed by similar parameters. Chemical structure, flexibility, and mobility of chains, the available free volume during polymerization, the degree of conversion, the extent of chain entanglements, the degree of phase separation, and the presence of chemical or physical cross-links are a few of the morphological features and physical phenomena [7] with strong influence on polymerization.

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Enhancement of mixing performance of single-screw extrusion processes via chaotic flows: Part II. numerical study

Cited by 34 publications

References 0 publications

A barrier embedded chaotic micromixer

A barrier embedded chaotic micromixer

Improved serpentine laminating micromixer with enhanced local advection

Evolution of Nonlinear Rheology and Network Formation during Thermoplastic Polyurethane Polymerization and Its Relationship to Reaction Kinetics, Phase Separation, and Mixing

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