• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.159-162
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• 2007

The characteristic of air-assist spray injected into subsonic crossflow were studied experimentally. External-mixing air assist injector of Orifice nozzle with L/d of 3 were tested with various air-liquid ratio. Shadowgraph photography was performed for spray visualization and trajectory of spray measurements. The detailed spray structure was characterized in terms of SMD, velocity, and volume flux, using PDPA. Experimental results indicate that penetration length was increased and spray distribution was accelerated by increasing air-liquid ratio.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.712-716
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• 2003

In the present study, the gas injection system based on air-water model was designed to investigate the behavior characteristics of bubbles injected into a ladle. The parameters such as gas volume fraction and bubble rise velocity were exprementally measured in a gas-liquid flow region. To measure gas volume fraction, an electo-conductivity probe was used and bubble rise velocity was obtained by a high speed CCD camera. Gas volume fraction was symmetric to the axis of nozzle secured on the bottom of a ladle. The bubble rise velocity was calculated for two different experimental conditions. That is, gas flow conditions were following two case: 1) Q = $0.63{\times}10^{-4}$ $m^{3}/s$, 2) $1.26{\times}10^{-4}$ $m^{3}/s$. As a gas injected into the liquid ladle, the liquid-phase region is circulated by bubbles' behavior. The bubble rise velocity was influenced of the circulation flow of liquid phase. As a result, the bubble rise velocity was appeared higher middle region of ladle than near the nozzle.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.148-157
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• 1998

This study presents test results of a residential window air-conditioner using R22 and two potential alternative refrigerants, R407C and R410B. A series of performance tests has been carried out for the basic and liquid-suction heat exchange cycles in a psychometric calorimeter test facility. For R407C, the same rotary compressor was used as in the R22 system. However, compressor for the R410B system was modified to provide the similar cooling capacity. The evaporator circuit was changed to get a counter-cross flow heat exchanger to take advantage of zeotropic mixture's temperature glide, and liquid-suction heat exchange cycle was also considered to improve the system performance. Test results were compared with those for the basic R22 system. The modified system with a liquid-suction heat exchanger increased cooling capacity and energy efficiency by up to 5%.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.27-36
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• 2000

In this study, spray characteristics of a dual airblast atomizer are addressed. Three dimensional characteristics of a dual airblast atomizer with air swirl are measured to provide the significant data. The liquid flow rate was fixed at 0.06 kg/min, and atomizing air was controlled at the liquid-air mass ratio of 4.0. The performance of the spray with co-swirl and counter-swirl flow was investigated at each point in the developed spray region using a three-component phase Doppler particle analyzer. This instrument was also used to evaluate the concentration profiles. The three dimensional mean velocity were investigated of present flow characteristics of the dual airblast atomizer. In addition, drop size distributions, mean droplet size profile, and droplet concentration were analyzed to understand atomization characteristics. This experimental results can be conveniently utilized for the preliminary design of gas turbine engines for aircraft.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.264-269
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• 2007

The microchannel waterblock has a good capability in the cooling of electronic devices. The object of this paper is to study on thermal performance of microchannel water block for cooling of CPU in desktop. The effects of header shape, liquid flow rate, and inlet temperature on the thermal performances of microchannel waterblock are investigated experimentally. Three types of waterblock with different header shape are manufactured from the micro milling and brazing processing. The experiments are conducted using water, over a liquid flow rate ranging from 0.7 to 2.0 LPM and inlet temperature ranging from 20 to $35^{\circ}C$. Waterblocks are attached both horizontally and vertically on the test section to anticipate a performance of waterblock under the actual state in computer. The base temperature and thermal resistance decrease with increasing of liquid flow rate. It was found that the sample #1 was appropriate for the prototype of liquid cooling system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.7
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• pp.385-389
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• 2017

Generally, refrigerant temperature out of the receiver is assumed to be saturated. This may be true for horizontal or vertical receivers having small aspect ratio. However, this assumption needs verification for vertical receiver having large aspect ratio. No study has reported information on this issue. The objective of this study was to determine the effect of liquid level and mass flow rate on liquid subcooling of a long vertical receiver using R-410A. During the test, inlet subcooling was maintained at $5^{\circ}C$ while saturation temperature was maintained at $10^{\circ}C$. Results showed that subcooling was maintained for the long vertical receiver. Subcooling preservation ratio (ratio of exit to inlet subcooling) was increased as mass flow rate or liquid level was increased. As a whole, 50 to 70% subcooling preservation was possible for the present receiver. Further investigations are needed to enhance information on this issue using receivers having different aspect ratios.

• Journal of ILASS-Korea
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• v.17 no.1
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• pp.35-44
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• 2012

To improve the mixing and atomizing performance at the center region of the conventional coaxial shear injector spray, the concept of a coaxial porous injector was invented. This novel injection concept for liquid rocket engines utilizes the Taylor-Culick flow in the cylindrical porous tube. The 2-dimensional injector, which can be converted in three injection configurations, was fabricated, and several cold flow tests using water-air simulant propellant was performed. The hydraulic characteristics and the effects of a gas flow condition on the spray pattern and the Sauter mean diameter (SMD) was analyzed for each configuration. The atomizing mechanism of coaxial porous injector was different with the coaxial shear injector, and it was explained by the momentum of the gas jet, which is injected normally against the center liquid column, and by the secondary disintegration at the wavy interface of liquid jet, which was generated at the recessed region. The SMD of 2D coaxial porous injector, which has higher gas momentum, was measured and it shows better atomizing performance at the center and outer side of spray than the 2D coaxial shear injector.

• International Journal of Fluid Machinery and Systems
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• v.7 no.2
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• pp.54-59
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• 2014

Particle Image Velocimetry combined with developed image processing method is adopted to study the liquid-solid two phase flow in the centrifugal pump impeller with crystallization phenomenon. The tracer particle is used to follow the liquid phase, which has the diameter between 8 to $12{\mu}m$. The crystal particle precipitates from the sodium sulfate solution does change the wavelength of the laser, and which has great laser scattering characteristics. The diameter of the crystal particle is larger than $20{\mu}m$. Through calculating the diameter of the particles in the image, the tracer particle and the crystal particle can be distinguished. By analyzing the experimental result, the following conclusion has been obtained. During the delay period, there is not any crystal particle and the pump performance has not been changed. As the crystallization process begins, the crystal nuclei appears from the supersaturation solution and grows larger with temperature decreasing, which has the tendency of moving towards the pressure side. The characteristics of liquid-solid two phase flow with crystallization phenomenon in the pump are obtained according to analysis of experimental results, and some guiding advices are presented to mitigate the crystallization phenomenon in pump impeller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.366-372
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• 2001

The ice plugging process consists of placing liquid nitrogen around a pipe and removing heat until the water in the pipe freezes and provides a solid plug or seal against fluid movement. This technique enables us to repair or inspect a pipe system without shutdown of entire system. A set of test apparatus for investigation of the liquid freezing phenomena during ice plugging is prepared. This study shows the characteristics of the liquid freezing and the heat transfer with various pipe and freezing jacket conditions. And in case there is flow of the fluid inside the pipe, the flow rate which can be able to form the ice plug is identified with the effect of the pipe diameter and freezing jacket length on the plug formation. The permissible maximum flow rate for the complete plug formation is approximately proportional to the freezing jacket length at the same pipe diameter condition.