• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2811-2816
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• 2007

We conducted a numerical study of AC-electroosmotic (alternating current) effect on the fluid flow and mixing in a 3-D microchannel. The microchannel used as an efficient micro-mixer is composed of a channel and a series of pairs of electrodes attached in zigzag pattern on the bottom wall. The AC electric field is applied to the electrodes so that a steady flow current takes place around the electrodes. This current is flowing across the channel and thus contributing to the mixing of the fluid within the channel. We performed numerical simulations by using a commercial code to obtain a steady flow field. This steady flow is then used in evaluation of the mixing performance via the concept of mixing index. It was found that good combination of two kinds of electrode, which gave us a good mixing, is not simple harmonic. And when the length ratio of these two kinds of electrode is 2:1, we can get the best mixing effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.707-715
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• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method is employed to simulate two-phase flow of low Reynolds number in a micro-channel. The mixing characteristics in a micro-channel is a function of Peclet number. The mixing length increases with the Peclet number. It is found that with the inclusion of static elements at the channel, rapid mixing of two liquids can be achieved, as shown by the results of computer simulations. The enhancement in mixing performance is thought to be caused by the generation of eddies and by lateral velocity component when the mixture flows past static elements. The results indicate that the size of static element has more effect on the mixing than the number of static element.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1369-1376
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• 2005

Effective mixing gives strong advantageous impact on microfluidic applications since mixing is in general very slow process motivated by molecular diffusion transport only on the micro-scale. In this work, the mixing characteristics are analyzed in a Y-channel micromixer with obstacles. For the through analysis, our laboratory in-house unstructured grid CFD code is validated through solving a concentration transport in a uniform microchannel. The solutions well correspond to both exact solutions and those from MemCFD. Mixing in a Y-channel micromixer with obstacles is numerically investigated by the in-house code to search the optimal radius and layout of obstacles. From the simulations, the mixing efficiency appears to be proportional to the magnitude of the formation of lateral velocity component. It is also shown that the asymmetric layout and radius enlargement of obstacles greatly improves mixing efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1307-1312
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• 2005

Turbulent in-situ mixing process is a new material process technology to get dispersed phase in nanometer size by controlling reaction of liquid/liquid, liquid/solid and liquid/gas, flow and solidification speed simultaneously. In this study mixing, the key technology to this synthesis method will be studied by computational fluid dynamics. For the simulation of mixing of liquid metal, static mixers will be investigated. Two inlets for different liquid metal meet and merge like 'Y' shape tube. The tube has various shapes such as straight and curved. Also, the radius of curve will be varied. The performance of mixer will be evaluated with quantitative analysis with coefficient of variance of mass fraction. Also, detailed plots of intersection will be presented to understand effect of mixer shape on mixing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.24-31
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• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In thi present study, the large scale vortex flow(LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about 35 $D_H$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane. Heat transfer in the rod bundle occurs greatly at the same direction to cross flow, and maximum temperature at the surface of bundle drops about 1.5K

• Journal of computational fluids engineering
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• v.22 no.1
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• pp.1-7
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• 2017

The mixing of water and chemicals is an important process in the water purification plant. In this paper, we compare PDM(pump diffusion mixer) and hydraulic mixer at the basin in the mixing process. The proper flow rates are predicted and compared in both mixers using CFD technique. As a result, the flow rate of purifier chemical liquid should be 5% of that of water for the optimal performance of mixing process. The characteristics of the two mixing methods are compared with each other for strong and weak points on the operation of the purification system, discussed in the view point of CFD simulations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.811-818
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• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In the present study, the large scale vortex flow (LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about $35D_h$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2708-2713
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• 2007

The aim of this paper is further studies to achieve deeper understanding in this field. First investigate the influence of operating conditions and design parameters on the hydrodynamics and the mass transfer properties of a loop reactor. This paper provides a literature review on the ejectors applications in the mixing system. A number of studies are grouped and discussed in several topics such as the background, theory of ejector, mixing characteristics, optimization of the system. Since the high efficiencies reactor using ejector widely used in gas-liquid system, especially in a number of chemical and biochemical processes. This is due to their high efficiency in gas dispersion resulting in high mass transfer rate and low power requirements. Thus ejector has been applied to the mixing system. An investigation on hydrodynamics and mass transfer characteristics of gas-liquid ejector has been carried out using three-dimensional CFD modeling.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.106-110
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• 2004

Generally, flow around a bluff body such as a circular cylinder is complicated compared with that around a streamlined body because of the existence of separated shear layers. Long bluff body such as a flat blunt plate is more complicated than short bluff body, because of separated-and-reattaching flow on the after bodies.(omitted)

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.3
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• pp.37-42
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• 2003

Physical properties of paper can be explained in terms of the changes in fiber's morphological properties. As the paper machine speed increases, the basis weight decreases and the mixing ratio of inferior recycled fibers increases, paper break becomes important than ever before. One of the objectives of this study is to analyze paper's physical, mechanical and fracture mechanical properties depending on softwood(SW) and hardwood(HW) mixing ratios and recycling. Fibers were refined by Valley beater to 450 mL CSF. Handsheets of 30 g/$\textrm{m}^2$ were prepared at different mixing ratios. Fracture toughness was measured as the amount of energy applied to cracked sample before total failure. Fracture toughness showed different trend to other strength properties. At the mixing ratio of SW 80: HW 20, papers showed the maximum fracture toughness. At this mixing ratio, flexible softwood fibers were mostly broken and stiff hardwood fibers were mostly pulled out.