• Structural Engineering and Mechanics
• /
• 제58권1호
• /
• pp.93-102
• /
• 2016

This article presents an experimental study on the effect of temperature and solid volume fraction of nanoparticles on the dynamic viscosity for the CuO/EG-water nanofluid. Nanoparticles with diameter of 40 nm are used in the present study to prepare nanofluid by two-step method. A "Brookfield viscometer" has been used to measure the dynamic viscosity of nanofluid with solid volume fraction up to 2% at the temperature range between 20 to $60^{\circ}C$. The findings have shown that dynamic viscosity of nanofluid increases with increasing particle volume fraction and decreasing temperature. Nine different correlations are developed on experimental data point to predict the relative dynamic viscosity of nanofluid at different temperatures. To make sure of accuracy of the proposed correlations, margin of deviation is presented at the end of this study. The results show excellent agreement between experimental data and those obtained through the correlations.

• Tribology and Lubricants
• /
• 제25권4호
• /
• pp.236-242
• /
• 2009

Oil viscosity is one of the important parameters for machinery condition monitoring. Basically, it is expressed as kinematic viscosity measured by capillary flow and dynamic or absolute viscosity measured by rotary shear viscometry. Recently, acoustic wave techniques appear in the market, measuring viscosity as the product of dynamic viscosity and density. For Newtonian fluids, knowledge of density allows conversion from one viscosity parameter to the other at a specific shear rate and temperature. In this work, oil samples with different chain lengths of viscosity index (VI) improvers and concentrations were examined by different viscometric techniques. Results showed that acoustic viscosity measurements give misleading results for oil samples with high molecular weight VI improvers and at low temperatures ${\leq}40^{\circ}C$.

• 공업화학
• /
• 제20권4호
• /
• pp.411-415
• /
• 2009

고점도인 최저급 폐유를 난방유로 대체하기 위하여 폐유에 희석용제로 경유,벙커C유를 이용하여 일정비율로 혼합한 후 연료 특성을 분석하였다. 혼합조건은 교반속도 3400~3600 rpm에서, 반응 시간을 30 s~30 min으로 조절하였고 반응온도는 $75{\pm}5^{\circ}C$로 유지하였다. 벙커C유, 경유를 이용하여 폐유의 점도를 낮춘 결과 최소 81%, 최대 96% 정도 감소되었다. 난방연료로서 폐유 : 벙커C유 : 경유의 최적 혼합 비율은 1 : 1 : 1이었으며 이 경우 인화점 $78^{\circ}C$, 동점도 $20.02mm^{2}/s$, 발열량 9158 kcal/L을 가짐을 확인하였다.

• 한국화재소방학회논문지
• /
• 제22권5호
• /
• pp.79-82
• /
• 2008

바이오디젤은 식물성기름등으로부터 제조시 메탄올과의 반응으로부터 제조되므로 바이오디젤의 잔존 메탄올은 화재폭발위험성을 높일 수 있다. 바이오디젤에 존재하는 메탄올의 위험도를 측정하기 위하여 바이오디젤에 메탄올을 일정 비율로 첨가하여 인화점과 동점도를 측정하였다. 바이오디젤의 인화점은 메탄올의 증가에 따라 현저히 감소하였으며 동점도도 감소하는 것으로 나타났다. 실험결과 바이오디젤 연료에 반응물 메탄올이 잔존하거나 또는 연료의 점성을 낮추기 위하여 첨가되는 메탄올은 바이오디젤의 인화점을 낮추어 화재폭발 위험성이 높은 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 추계학술대회 논문집
• /
• pp.573-576
• /
• 1995

The realization by many industrial countries that manufacturing is a critical ingredient for attaining economic strength and stability has led to the development of automated systems which were proviously considered as gimmicks. The adaptive skill of the human operator is now being simulated and reproduced by computer that have become more powerful and less expensive. The work presented in this paper forms an investigation of the effects of dynamic viscosity and load of hydraulic oil an pressures with three different circuit(meter-in, meter-out and bleed off). The experimental results showed that pressures increase with an increase in dynamic viscosity and load in bleed off circuit, but there is no variation of pressure in meter-In meter-out circuit.

• 오토저널
• /
• 제8권4호
• /
• pp.66-72
• /
• 1986

Numerical analysis has been made on the dynamic behavior of a supporting structure subjected to a force of time dependent frequency. The effect of solid viscosity is studied when the frequency of external force passes through the first critical frequency of the simple beam for four times. Within the Euler-Bernoulli beam theory, the solutions are obtained by using finite Fourier and Laplace transformation methods with respect to space and time variables. The result shows that the maximum value of the dynamic deflection is considerably affected by the value of the solid viscosity as well as the frequency difference The maximum dynamic deflection is found to occur in the frequency lower limit C of 0.85-0.985 in the presence of the solid viscosity.

• Korea-Australia Rheology Journal
• /
• 제20권4호
• /
• pp.213-220
• /
• 2008

The effects of temperature on the rheological properties of the solutions of poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) in dimethyl acetamide (DMAc) were investigated in terms of frequency and concentration. The effects of temperature on the intrinsic viscosity of the solutions were discussed. In dynamic rheological measurement, the concentrated solutions showed a little unexpected rheological response; as temperature was increased dynamic viscosity was increased and the solutions exhibited more noticeable Bingham body character over the temperature range, 30 to $70^{\circ}C$. In addition, the solution gave longer relaxation time, lower value of loss tangent and higher value of yield stress at higher temperature and at higher concentration. On the other hand, the dilute solutions revealed that intrinsic viscosity was decreased and its Huggins constant was increased with increasing temperature. These physical parameters suggested that the increase of viscosity with increasing temperature resulted from the localized gelation of PVDF-HFP due to reduced solubility to the solvent.

• 유변학
• /
• 제9권1호
• /
• pp.27-32
• /
• 1997

GM 은 Amorphopallus Konjac K. Koch의 tuber의 주성분으로알카리 응고제를 첨가 함에 따라 열적으로 안정한 gel을 형성한다. GM에 침전제로 메탄올을 사용하여 4단계로 분 별하였고 각 분별물(F.1, F.2, F.3, F.4)들은 Mark-Houwink 식을 이용하여 분자량을 산출하 였다. Ubbelohde를 이용한 농도에 따른 환산점도로부터 고유 점성도값을 구한 결과 분자량 이 높은 분별물이 분자량이 낮은 분별물에 비하여 직선으로부터 벗어남을 알수 있었다. 또 한 고유점성도는 분자량이 증가할수록 증가하였고, 분자량 분포 범위가 broad하게 나타났다. GM용액의 frequency와 shear rate에 따른 viscosity를 측정한결과 낮은 frequency에서는 loss modulus(G＂)가 storage modulus(G＂)보다 큰 값을 가졌으나 높은 frequency에서는 G ＇가 G＂보다 크게 나타났다. 이 현상은 분자들의 얽힘에 관한 시간 의존도로써 설명할수 있다. 즉높은 frequency에서는 탄소 사슬간의 얽힘들이 진동기간내에 분자결합이 끊어지기 에 충분한 시간을 갖지 못하여 그 조직이 교차 결합을 한 gel처럼 행동하게 되고 한편 낮은 frequency에서는 탄소사슬들의 얽힘이 풀리고 흐르기에 충분한 시간을 갖게된다. Shear rate에 따른 viscosity값과 frequency에 대한 dynamic viscosity값은 거의 유사한 변화를 나 타내었다.

• 펄프종이기술
• /
• 제43권3호
• /
• pp.121-127
• /
• 2011

This study used two types of rheology modifiers including an alkali-swellable emulsion (ASE) and an surface-adhesion emulsion (SAE) to elucidate their effects on high shear viscosity and dynamic penetration behavior among the flow properties of high solids coating. Since rheology under high shear and dynamic penetration behavior significantly affect the quality of coated paper in case of high solids coating, it is very important to examine the variations in rheology of high solids coating color by rheology modifier. It was found that the high solids coating color prepared with the SAE type showed superior dynamic penetration behavior and high shear viscosity than that with the ASE type rheology modifier.

• 한국식품과학회지
• /
• 제29권5호
• /
• pp.932-938
• /
• 1997

Changes in viscosity and dynamic theological properties of Job's-tears were measured by Bohlin dynamic tester as a function of moisture, and measurement was performed within a linear viscoelastic range. The result of the shear stress vs shear rate of Job's-tears at different moisture contents $(50{\sim}75%)$ was applied to mathematical models and Herschel-Bulkley model showed the highest correlation coefficient. Lower moisture content (55%) produced higher yield stress and consistency index, but lower flow behavior index, whereas higher moisture content showed reverse effects. Job's-tears with $50{\sim}70%$ moisture contents showed a higher storage modulus (G') than loss modulus (G') at all frequencies, showing a higher concentrated polymer characteristics. However, higher moisture content (>75%) showed crossover point between G' and G', and frequency dependency. As the moisture content was increased, the amount of viscoelastic properties such as G', G', complex viscosity decreased during heating, and initial temperature and miximum value of viscoelastic properties shifted to higher temperatures, representing the moisture-dependence of Job's-tears upon theological properties.