• 분석과학
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• 제32권3호
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• pp.77-87
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• 2019

High viscosity carbon black dispersions are used in various industrial fields such as color cosmetics, rubber, tire, plastic and color filter ink. However, carbon black particles are unstable to heat due to inherent characteristics, and it is very difficult to keep the quality of the product constant due to agglomeration of particles. In general, particle size analysis is performed by dynamic light scattering (DLS) during the dispersion process in order to select the optimum dispersant in the carbon black dispersion process. However, the existing low viscosity analysis provides reproducible particle distribution analysis results, but it is difficult to select the optimum dispersant because it is difficult to analyze the reproducible particle distribution at high viscosity. In this study, dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) analysis methods were compared for reproducible particle size analysis of high viscosity carbon black. First, the stability of carbon black dispersion was investigated by particle size analysis by DLS and AsFlFFF according to milling time, and the validity of analytical method for the selection of the optimum dispersant useful for carbon black dispersion was confirmed. The correlation between color and particle size of particles in high viscosity carbon black dispersion was investigated by using colorimeter. The particle size distribution from AsFlFFF was consistent with the colorimetric results. As a result, the correlation between AsFlFFF and colorimetric results confirmed the possibility of a strong analytical method for determining the appropriate dispersant and milling time in high viscosity carbon black dispersions. In addition, for nanoparticles with relatively broad particle size distributions such as carbon black, AsFlFFF has been found to provide a more accurate particle size distribution than DLS. This is because AsFlFFF, unlike DLS, can analyze each fraction by separating particles by size.

• 설비공학논문집
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• 제19권8호
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• pp.593-598
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• 2007

The present study has dealt with the measuring method of ice slurry viscosity using falling sphere viscometer. The experimental apparatus was composed by test section and high-speed video system. And the spheres used in this study were alumina and glass. The main parameters were ice packing factor (IPF) and falling velocity of sphere so the acquired results were discussed for these parameters. The viscosity of ice slurry was calculated by using measured falling velocity and moving distance at instantaneous time and the Stokes hypothesis was used for this calculation. It was clarified that possible measuring range was $IPF\;=\;0.06{\sim}0.14$ of this type of measuring device and measuring method. In addition, it was clarified that the viscosity of ice slurry increased to increase of ice packing factor (IPF) of ice slurry.

• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.395-402
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• 2002

This paper shows how to formulate the transient analysis of 2-dimensional Hagen-Poiseuille flow using smoothed particle hydrodynamics (SPH). Treatments of viscosity, particle approximation and boundary conditions are explained. Numerical tests are calculated to examine effects caused by the number of particles, the number of particles per smoothing length, artificial viscosity and time increments for 2-dimensional Hagen-Poiseuille flow. Artificial viscosity for reducing the numerical instability directly affects the velocity of the flow, though effects of the other parameters do not produce as much effect as artificial viscosity. Numerical solutions using SPH show close agreement with the exact ones for the model flow, but SPH parameter must be chosen carefully Numerical solutions indicate that SPH is also an effective method for the analysis of 2-dimensional Hagen-Poiseuille flow.

• 한국자동차공학회논문집
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• 제2권4호
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• pp.9-17
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• 1994

Effect of Newtonian and non-Newtonian oils on minimum ol film thickness in engine journal bearing were investigated at various oil viscosities. The influence of oil viscosity and engine operating conditions on minimum oil film thickness of main bearing and con-rod bearing was examined. Minimum oil film thickness for Newtonian oils increased uniformly with kinematic viscosity. But the correlation between kinematic viscosity and minimum oil film thickness was very poor for non-Newtonian oils. According to the straight-line regression analysis for non-Newtonian oils, high temperature high shear viscosity at 1 $1{\times}10^6Sec^{-1}$, $150^{\circ}C$ increase the coefficient of determination from 0.41 to 0.77. Con-rod bearing showed better correlation between minimum oil film thickness and engine operating conditions than main bearing.

• 한국분무공학회지
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• 제4권4호
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• pp.24-29
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• 1999

In the pressure swirl atomizer, the liquid is injected through tangential passages into a swirl chamber, from which it emerges with both tangential and axial velocity components to form a thin conical sheet at the nozzle exit. This sheet rapidly attenuates, finally disintegrating into ligaments and then drops. The purpose of this study is to measure the spray characteristics according to variation of viscosity of the spray produced by the pressure swirl atomizer. The nozzle tested here were especially designed for this investigation. The discharge coefficient is determined by measuring the volume flow rate with a flow meter and the cone angle of the liquid sheets issuing from the nozzle is obtained from series of photographs of the sheet for various liquid viscosity and injection pressure. And mean drop size is measured by image processing method. It is found that the geometrical characteristics of the nozzle and the variation of viscosity were the influential parameters to determine the spray characteristics such as the cone angle, discharge coefficients and SMD.

• 대한화장품학회지
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• 제42권2호
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• pp.127-133
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• 2016

본 연구에서는 정제수/Span 80-Nikkol BL 25/오일계의 water-in-oil (W/O) 나노에멀젼을 높은 온도에서 PIC 유화로 제조하였다. 이 방법은 본 시스템에서 미세하게 분산된 저점도의 W/O 나노에멀젼의 형성을 가능케 하였다. 그러나 실온에서 PIC 방법으로 제조된 에멀젼은 나노에멀젼보다는 마크로에멀젼이 제조되었다. 유화온도가 $30^{\circ}C$에서 $80^{\circ}C$로 증가하면 온도에 따른 계면장력의 큰 변화의 결과로 입자 크기는 $2{\mu}m$에서 100 nm 정도로 감소하였다. $80^{\circ}C$에서 제조된 나노에멀젼의 입자 크기는 50 ~ 200 nm 범위에 있었고 내상의 분율은 15 wt%까지 가능하였다. 또한 혼합 유화제의 최적 HLB는 7.0 부근에서 가장 안정한 나노에멀젼이 형성되었다. 제조된 나노에멀젼은 1개월 이상 실온에서 안정하였다. 본 연구 결과는 저점도의 W/O 나노에멀젼의 형성 최적화에 중요한 정보를 제공할 수 있다. 이 결과는 W/O 나노에멀젼의 저점도로 인한 부드러운 사용감 등으로 화장품 제형으로 유용하게 이용될 것으로 생각된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1752-1757
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• 2008

Simple and highly efficient droplet merging method is proposed, which enables two nanoliter or picoliter droplets to merge regularly in a straight microchannel. We observe that two droplets of the same size but of different viscosities are merged by velocity difference induced as they are transported with the carrier fluid. To make viscosity difference, the mass ratio of water and glycerol is varied. Two droplets of the same size or of different sizes are generated alternatingly in the cross channel by controlling flowrates. This droplet merging method can be used to mix or encapsulate one target sample with another material, so that it can be applied to cell lysis, particle synthesis, drug discovery, hydrogel-bead production, and so on.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1327-1334
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• 2003

Flow characteristics of the fluid laden with many particles in the two-dimensional channel are investigated using the Navier-Stokes equations coupled with the equation of motion of particles by direct numerical simulation. A four-step fractional step method with Crank-Nicolson scheme and ALE technique is used for P2P1 mixed finite element method. The motion and distribution of particles in the fluid is virtually described as a result of direct numerical simulation and the increase of viscosity is compared with theoretical equations. The effect of channel height on the relative viscosity and the tubular pinch effect are discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.786-791
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• 2003

We have studied on the main causes of pressure drop in the paint hose under the spraying with airless spray pump and suggest calculation method for selecting the optimum pressure drop during the spraying. Among many factors contributing the pressure drop during the airless spraying procedure of paint, some of the key factors and the correct method for checking pressure loss between airless pump and spray gun are addressed. We have developed pressure loss calculation method which depending on hose length and diameter, viscosity and flow rate in the painting hose during the spraying. also we have developed calculation equation for the expected spray tip flow rate which depending on pressure and specific gravity and tip size.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권12호
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• pp.573-577
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• 2005

[$TiO_2$] sol and $SiO_2$ sol were prepared using sol-gel method. As $H_{2}O$/Alkoxide ratios increased, sol had cluster structure and as $H_{2}O$/Alkoxide ratios decreased, sol had linear structure. Gelation time of $TiO_2$ sol was faster than that of $SiO_2$ sol according to the time. In comparison with initial viscosity between $TiO_2$ sol and $SiO_2$ sol, $TiO_2$ sol was highest at $H_{2}O/Ti(OC_{3}H_{7})_{4}=5$, $SiO_2$ sol was almost constant according to $H_{2}O/Si(OC_{2}H_{5})_{4}$ ratios.