• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2568-2573
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• 2008

A drop impact on the liquid film/pool generates several phenomena such as the drop floating, bouncing, formation of vortex ring, jetting, bubble entrapment and splashing. These phenomena depend on the impact velocity, the drop size, the drop properties and the liquid film/pool thickness. These parameters can be summarized by four main dimensionless parameters; Weber number, Ohnesorge number, Froude number and non-dimensional film/pool thickness. In the present study, the phenomena of the splashing and bubble entrapment due to the drop impact on the liquid film/pool were numerically investigated by using a Level Set method for the sharp interface tracking of two distinct phases. After the drop impact, the splashing phenomena with the crown formation and spreading were predicted. Under the specific conditions, the bubble entrapment at the base of the collapsing cavity due to the drop impact was also observed. The numerical results were compared to the available experimental data showing good agreements.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.34-38
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• 2005

Characteristics of size, rising velocity and distribution of liquid drops have been investigated in a immiscible liquid-liquid fluidized-bed whose diameter was 0.102 m and 2.5 m in height. Effects of velocities of dispersed (0~0.04 m/s) and continuous (0.02~0.14 m/s) liquid phases and fluidized particle size (1, 2.1, 3 or 6 mm) on the liquid drop properties in the extractor have been determined. The resultant flow behavior of liquid drops became more complicated with increasing the velocity of dispersed or continuous liquid phase. The resultant flow behavior of liquid complicated with increasing the velocity of dispersed or continuous liquid phase. The resultant flow behavior of liquid drops depended strongly upon the drop size and its distribution. The drop size increased with increasing dispersed phase velocity, but decreased with increasing particle size. However, the size of liquid drop exhibited a local maximum with increasing continuous liquid velocity. The size and rising velocity of liquid drops have been well correlated in terms of operating parameters.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.37-44
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• 2000

High velocity, gas-assisted liquid drop trajectories were investigated under well-controlled experimental conditions at elevated gas densities and room temperature. A monodisperse stream of drops which are generated by a vibrating-orifice drop generator were injected into a transverse high velocity gas stream. The gas density and air jet velocity were adjusted independently to keep the Weber numbers constant. The Weber numbers studied were 72, 148, 270, 532. The range of experimental conditions included studied the three drop breakup regimes previously referred as bag, stretching/thinning and catastrophic breakup regimes. High-magnification photography and conventional spray field photographs were taken to study the microscopic breakup mechanisms and the drop trajectories in high velocity gas flow fields, respectively. The parent drop trajectories were affected by the gas density and the gas jet velocities and do not show similarity with respect to the either Weber or the Reynolds number, as expected.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4053-4061
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• 1996

Internal flow characteristics within Y-jet atomizers and the local drop size distribution and cross-sectional averaged drop size at the outside were investigated with the liquid and air injection pressures, mixing port length of atomizers, and the liquid properties taken as parameters. To examine the effect of the liquid viscosity, glycerin-water mixtures were used in this study. The liquid viscosity plays only a minor role in determining the internal flow pattern and the spatial distribution shape of drops, but the drop sizes themselves generally increase with increasing of the liquid viscosity. An empirical correlation for the liquid discharge coefficient at the liquid port was deduced from the experimental results; the liquid discharge coefficient strongly depends on the liquid flow area at the mixing point which is proportional to the local volumetric quality(.betha.$_{Y}$), and the volumetric quality was included in the correlation. Regardless of the value of the liquid viscosity, the compressible flow through the gas port was well represented by the polytropic expansion process(k=1.2), and the mixing point pressure could be simply correlated to the aspect ratio( $l_{m}$/ $d_{m}$) of the mixing port and the air/liquid mass flow rate ratio( $W_{g}$/ $W_{f}$) as reported in the previous study.udy.udy.y.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.538-546
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• 1989

Effect of liquid viscosity was studied experimentally on the drop size distributions of the liquid sprays from swirl atomizers. Glycerine-Water mixtures were used as test fluids for the experiments. Drop sizes of the liquid sprays were measured with the light scattering method. The concept of the standard deviation was introduced to represent the degree of uniformity of the drop size distributions. Experimental results show that the spray drops become coarser and less uniform with the liquid of higher viscosity. The effect of viscosity on the Sauter mean diameter and the standard deviation appeared to be more significant with the lower injection pressure. It was also confirmed that the Sauter mean diameter increases with the increase of the liquid viscosity and with the decrease of the injection pressure.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3229-3235
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• 2021

The key process used in nuclear industries for the management of radiotoxicity associated with spent fuel in a closed fuel cycle is solvent extraction. An understanding of hydrodynamics and mass transfer is of primary importance for the design of mass transfer equipment used in solvent extraction processes. Understanding the interfacial phenomenon and the associated hydrodynamics of the liquid drops is essential for model-based design of mass transfer devices. In this work, the phenomenon of drop formation at the tip of a nozzle submerged in quiescent immiscible liquid phase is revisited. Previously reported force balance based models and empirical correlations are analyzed. Experiments are carried out to capture the process of drop formation using high-speed imaging technique. The images are digitally processed to measure the average drop diameter. A correlation based on the force balance model is proposed to estimate drop diameter and jet length. The average drop diameter obtained from the proposed model is in good agreement with experimental data with an average error of 6.3%. The developed model is applicable in both the necking as well as jetting regime and is validated for liquid-liquid systems having low, moderate and high interfacial tension.

• Journal of ILASS-Korea
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• v.3 no.2
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• pp.1-13
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• 1998

A theoretical and experimental study was carried out to predict the drop size distribution of the pressure swirl atomizer. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed that the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. Drop size distribution was obtained by using maximum entropy formalism. Seven constraints in the form of the definition of mean diameter were used in this formulation in order to avoid the difficulties of estimating source terms. In this study $D_{10}$ only was introduced into the formulation as a constraint. The predicted drop size and drop size distribution agreed well with the measured data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.6 s.237
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• pp.747-754
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• 2005

Because the liquid-vapor interfacial shear stress affects seriously the liquid flow and the maximum heat transport rate of the grooved wick heat pipe, an accurate modeling for the pressure drop characteristics of the liquid flow is required. A novel method for calculating the liquid pressure drop and the velocity profile of an open channel flow in a microchannel with an arbitrary cross-section is suggested and validated by experiments. An experimental apparatus for the Poiseuille number of the liquid flow in open rectangular microchannels with the hydraulic diameters of 0.40mm, 0.43mm, 0.48mm is used in order to reproduce real situations in the grooved wick heat pipe. Analytic results from the suggested method are compared with the experimental data and they are in a close agreement with each other.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.1025-1033
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• 2001

A scaling analysis is provided which predicts the sliding velocity of a liquid drop down an inclined surface. The analysis is based on the balance of the gravitational work rate that drives the drop sliding and the resistances by capillary and viscous forces. The capillary resistance is accounted for via the contact angle hysteresis, which is quantified by measuring the critical inclination causing the drop to start sliding. The sliding of the drop is governed by the rate of the viscous dissipation of the Stokes flow. The analysis result in its limit form for small contact angles is consistent with previous results. In the experiments to verify the analysis results, the measured sliding velocity of various liquid drops are shown to obey the predictions made in this study.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.1
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• pp.24-32
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• 2018

In this paper, analytical studies were conducted to obtain optimal design factors and analysis parameters of liquid nitrogen cooling exchanger applied in cryogenic refrigerator. The target value of heat transfer rate was more than 1 kW and pressure drop was less than 40 kPa. Design factors of cryogenic heat exchanger included width of channel and configuration of paths. Analytical factors of liquid nitrogen cooling exchanger included temperatures of coolant header surface and inlet liquid nitrogen. The width and number of channels in the design parameters were 0.0050~0.0150 m and 4~8, respectively. The configuration of channel path was 4 ways. Temperatures of coolant header surface and inlet liquid nitrogen in analytical parameters were 74 to 78K and 82 to 86K, respectively. As result, the design factor and analysis parameter satisfying the target values were obtained. The biggest heat transfer rate was 1.36 kW with pressure drop of 32.26 kPa.