• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.195-201
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• 2007

A visualization study of flow characteristics in a mixer using multi-nozzle bubbling was performed. The mixer is filed with liquid glycerin (dynamic viscosity = $1000mPa{\cdot}s\;at\;25^{\circ}C$) and convective mixing is induced by air bubbles generated from 9 orifices installed on the bottom of the mixer. To visualize the flow field, PIV (Particle Image Velocimetry) system consisting of 532nm Nd:YAG laser, $2k{\times}2k$ CCD camera and synchronizer is adopted. The bubbles generated with uniform size and frequency form bubble stream and bubble streams rise vertically without interaction between bubble streams. Mixing efficiency is affected by the height of bubbler and the effective height of bubbler is 20nm from the bottom of the mixer.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.48-54
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• 2006

A visualization study of flow characteristics in a mixer using multi-nozzle bubbling was performed. The mixer is filled with liquid glycerin (dynamic viscosity = $1000mPa{\cdot}$ s at $25^{\circ}C$) and convective mixing is induced by air bubbles generated from 9 orifices installed on the bottom of the mixer. To visualize the flow field, PIV (Particle Image Velocimetry) system consisting of 532nm Nd:YAG laser, $2k\times2k$ CCD camera and synchronizer is adopted. The bubbles generated with uniform size and frequency form bubble stream, and bubble streams rise vertically without interaction between bubble streams. Mixing efficiency is affected by the height of bubbler and the effective height of bubbler is 20mm from the bottom of the mixer.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.4
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• pp.11-16
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• 2002

Flow mechanism of peristaltic motion is numerically and experimentally investigated to obtain a propulsive force in highly viscous fluid. Computing code for the analysis of the motions is developed with cell-centered unstructured grid scheme. The computed results by the developed code is compared with the experimental results which have been carried out to find out the propulsion mechanism in highly viscous fluid. The computed results shows good correlation with the experimental results and further the propulsive force can be obtained by sinusoidal motion which makes a pressure difference on waving surface. The more computation with variation of Reynolds number and parameters of motion is expected for finding a proper working range.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.367-370
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• 2003

In this study the effects of fluid viscosity on the pump performances of a conventional centrifugal pump were experimentally studied. The study aimed to compare the pump characteristics for water and high viscosity fluids. The Working fluids are water, aqueous sugar solution and glycerin solution. The pump characteristics of total head and efficiency with high viscosity fluids were different. The performance curves of efficiency for the sugar and glycerin solutions were decreased up to 8.1% and 12.9% than that of water.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.604-613
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• 2002

Generation characteristics of electrospray droplets for highly viscous liquid have been investigated by measuring size distributions of droplets emitted from the Taylor cone using glycerol solutions with various conductivities. Because of very small volatility of glycerol, droplet sizes can be measured by an aerodynamic size spectrometer (TSI Aerosizer DSP) with negligible evaporation of droplets. For highly conducting and viscous liquid, the sizes of the droplets electrosprayed from the Taylor cone are found to be relatively insensitive to applied voltages and the electrosprays assisted by the corona discharge call produce monodisperse droplets as long as the corona intensity is not too high. Near the minimum flow rate where a liquid cone is stable, the spray tends to consist of a one -peak monodisperse distribution of drop lets. However, at high flow rates, the spray bifurcates into bimodal distributions, which are consistent with the result of the previous study for less viscous liquids than our liquids. For liquid flow rates (Q) below 1 nl/s, the measured droplet diameters by the aerosizer are in the range of 0.30 to 1.2 ${\mu}{\textrm}{m}$ for the glycerol solutions. The diameters of monodisperse droplets scale approximately with $r^*=Q_$\tau$(Q$\tau$){^1/3}$ where $r^*$ is a characteristic length and $\tau$is the electrical relaxation time of the fluid. However, when compared with several represe ntative scaling laws, the droplet diameters are two to six factors greater than those predicted by the scaling laws. This may be closely related to the combined effect of the much higher viscosity and the electrical charge on the jet breakup of glycerol so solution.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.516-521
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• 2014

Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02~0.1 m/s), liquid viscosity ($0.1{\sim}0.3Pa{\cdot}s$) and surface tension ($66.1{\sim}72.9{\times}10^{-3}N/m$) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; $$h=2502U^{0.236}_{G}{\mu}^{-0.250}_{L}{\sigma}^{-0.028}_L$$ $$Nu=325Re^{0.180}Pr^{-0.067}We^{0.028}$$.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.17-23
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• 1998

A simplified experiment was performed to figure out the atomization characteristics of highly viscous liquid of rice-bran oil by applying ultrasonic energy to improve the atomization of spray droplets. A spray system, an ultrasonic system, and three kinds of pintle-type nozzles(pin-edge angle: 5 , 10 , 15 ) were manufactured. To investigate the effects of ultrasonic energy on the atomization of a highly viscous liquid, a phase doppler particle analyzer was used for the measurement and calculation of spray droplets data. Nozzle opening pressures were chosen of 3 levels, i.e, 10, 13, 16 MPa. As a result, it could be concluded that the ultrasonic energy was effective to improve the spray atomization when applied to the fuel by means of 3 different nozzles because of the effects of the liquid fuel cavitation and relaxation between molecules caused by ultrasonic energy. The improvement rate of the spray atomization by the ultrasonic spray atomization by the ultrasonic spray compared with the conventional spray was about 10% increase in the case of pintle type nozzles. With the increase of pin-edge angles the distribution lines by nozzle opening pressures are declined for both conventional and ultrasonic sprays. This means that the increase of the pin-edge angle improves the atomization of sprays.