• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3045-3049
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• 2007

This paper presents a numerical study to enhance the mixing of polyurethane resin in a container. In general, the properties of polyurethane resin vary with the production environment, such as temperature. However in this study we assumed that the dynamic viscosity of the polyurethane is kept constant at 15 [Pa s]. We computed the flow solution and visualized the mixing pattern for different shapes of mixers by using commercial code, ANSYS CFX. In order to quantify mixing, we employed the concept of mixing index by volume integration.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.241-248
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• 2002

In this work, we calculated the vapor-liquid equilibrium of aqueous polymer solutions by using PRSV equation of state combined with $G^{ex}$ mixing rules(HVO, MHVL, MHV2, LCVM). From the comparison of calculated results with experimental data obtained from literature, we found that calculation results by using MHV1 mixing rule have showed small range of error than HVO, MHV2 and LCVM mixing rules. Calculation results by using the combination of MHV1 mixing rule and UNIFAC-FV model have showed the best result for selected aqueous polymer solutions.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.77-83
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• 2007

This paper presents numerical and experimental works for simultaneous pumping and mixing small liquid using asymmetric microelectrode arrays, based on AC electroosmotic flows. To this end, four arrangements of electrode pairs were considered with diagonal/herringbone shapes. Numerical simulations were made of three-dimensional geometries by using the linear theory. The results indicated that the helical flow motions induced by the electrode arrays play a significant role in the mixing enhancement. The pumping performance was influenced by the slip velocity at the center region of the channel compared to that near the side walls. To validate the numerical predictions, the microfluidic devices were made through MEMS. The flow rate was obtained by using micro PIV, increasing the applied frequency. The electrolyte was potassium chloride solution. The flow patterns above electrodes were visualized to see lateral flow for mixing. The experimental results showed good agreements with the numerical predictions.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.85-85
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• 2002

Lithiated transition metal oxides such as LiMn2O4, Lil-xMnO$_2$, LiNiO$_2$, LiCoO$_2$, and their solid solution phases are used as cathode materials for lithium rechargeable batteries. We prepared the cathode materials using a novel eutectic self-mixing method without any artificial mixing procedures. This method provides an extraordinarily simple way to make the cathode materials, and it is possible to prepare at very low temperature such as 25$0^{\circ}C$. Furthermore, the cathode materials produced have discharge capacities that are much better than cathode materials prepared by previously reported synthetic methods. The spontaneous and homogeneous mixing is verified by $^{7}$ Li magic-angle-spinning (MAS) NMR spectroscopy.

• Textile Coloration and Finishing
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• v.21 no.1
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• pp.21-29
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• 2009

In order to enhance the functionality of a cotton fabric actually used as a clothing material for patients, the fabrics were treated with a chitosan/nanosilver mixed solution. The nanosilver had excellent biocompatibility, provided expectation of an additional performance, did not harm human beings, and supplements chitosan, which was disadvantaged if used alone for fabric treatment. The nanosilver was mixed thereto and a treatment effect due to a mixing ratio was considered. This study was observed through mechanical properties and hand value which were the important function. The treatment of chitosan/nanosilver mixed solution gave a smoother surface than the treatment of chitosan alone. As a result of evaluation of the forms according to KES-FB system, Koshi was deduced, and both Numeri and Fukurami were increased. Thereby, the cotton fabric was a little smooth to provide elasticity, due to the treatment of chitosan/nanosilver mixed solution. THV of the treated fabrics calculated from this basis increased at all mixing ratio as compared with the untreated fabric. The fabrics treated with chitosan/nanosilver mixed solution were shown a better THV than the fabric treated with chitosan alone.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.43-54
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• 1997

This paper presents an approximate analytical solution to a two-region one-dimensional model for the charging process of stratified thermal storage tanks with variable inlet temperature in the presence of momentum-induced mixing. Based on the superposition principle, an arbitrary-varying inlet temperature is decomposed into inherent discontinuous steps and continuous intervals approximated as a finite number of piecewise linear functions. This approximation allows the temperature of the upper perfectly-mixed layer to be expressed in terms of constant, linear and exponential functions with respect to time. Applying the Laplace transform technique to the model equation for the lower thermocline layer subject to each of three representative interfacial conditions yields compact-form solutions, a linear combination of which constitutes the final temperature profile. A systematic method for deriving solutions to the plug-flow problem having polynomial-type boundary conditions is also established. The effect of adiabatic exit boundary on solution behaviors proves to be negligible under the actual working conditions, which justifies the assumption of semi-infinite domain introduced in the solution procedure. Finally, the approximate solution is validated by comparing it with an exact solution obtained for a specific variation of inlet temperature. Excellent agreements between them suffice to show the necessity and utility of this work.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.184-195
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• 1995

A theoretical one-dimensional model for the charging process in stratified thermal storage tanks is established presuming that the fluid ensuing from the tank inlet creates a perfectly mixed, layer above the thermocline. Both the generic and asymptotic closed-form solutions are obtained via the Laplace transformation. The asymptotic solution describes the nature of the charging pertaining to the case of no thermal diffusion, whereas the generic solution is of practical importance to understand the role of operating parameters on the stratification. The present model is validated through comparison with available experimental data, where they agree well with each other within a reasonable limit. An interpretation of the exact solution entails two important features associated with the charging process. The first is that an in-crease in the mixing depth $h_m$ causes a relatively slow temperature rise in the perfectly mixed region, but on the other hand it results in a faster decay of the overall temperature gradient across the thermocline. Next is the predominance of the mixing depth in the presence of the prefectly mixed region. In such a case the effect of the Peclet number is marginal and there-fore the thermal characteristics are solely dependent on the mixing depth paticularly for large $h_m$. The Peclet number affects significantly only for the case without mixing. Variation of the storage efficiency in response to the change in the mass flow rate agrees favorably with the published experimental results, which confirms the utility of the present study.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.751-757
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• 2011

Subminiature devices such as Lab-on-a-chip and p-TAS(Micro Total Analysis System) have been intensively studied in biotechnology and chemistry, In many cases, a micromixer was widely used to mix different solutions for synthesizing novel materials. However, in microfluidic system, there is generally a laminar flow under very small Reynolds number so it is difficult to mix each solution perfectly. To settle this problem, we propose a new mixing mechanism which generates a horizontal and vertical multi-mixing (HVM) flow for effective mixing within a short mixing section. We evaluated the proposed mechanism using CFD analysis, and the results showed that the HVM mechanism had a relative high-effectiveness comparing to the existing methods.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.459-462
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• 2001

Interface effects on properties of NTC thermistors having Mn-Co-O spinel crytal structure system are analyzed by a mixing rule in case of mixed types and layered types between CuO and $Al_{2}O_{3}$ added compounds. With adding CuO and $Al_{2}O_{3}$, The compounds form completely solid solution and their resistance and B constant are changed due to the variation of conduction electrons by their ionic substitutions. The properties of mixed NTC thermistors are depended on the logarithmic mixing rule by a dispersed phase and they show slightly lower values due to the lattice mixing affect in compared with calculated values. The resistance of layered NTC thennistors is depended upon the series mixing rule containing the value of an interface layer and effected by the variation of its thickness, and it is changed rapidly to the logarithmic mixing rule by the connection between two layers with increasing the interface layer.

• Elastomers and Composites
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• v.45 no.1
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• pp.17-24
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• 2010

Herein, the effect of the dispersion uniformity of the multi-wall carbon nanotube (MWCNT) on the thermal and electrical conductivity of polystyrene (PS)/MWCNT composite was investigated. The PS/MWCNT composites were prepared by solution mixing from dispersions of various MWCNTs in PS/tetrahydrofuran (THF) solution. Three types of MWCNTs were used; pristine MWCNT, hydroxyl functionalized MWCNT, which was functionalized with $KMnO_4$ in the presence of a phase transfer catalyst at room temperature, and pristine MWCNT with BYK-9077 as a dispersant. It was found that the stable dispersion state of MWCNT in PS/THF solutions significantly improved the thermal and electrical conductivity of the ultimate composites. It is noted that the thermal and electrical conductivity of PS/3 wt% pristine MWCNT composite with BYK-9077 were about 9.4 and 30~50% higher than those of PS/3 wt% pristine MWCNT composite, respectively.