• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.853-859
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• 2001

A pulsed tracer gas technique is applied to measure distributions of local mean age and residual life time of air in a half-scale experimental chamber. The room airflow patterns are flow-visualized by a Helium bubble generator for three different exhaust locations. A supply slot is located at the top of a right wall, and an exhaust slot is either at bottom-left(Case 1), bottom-right(Case 2), or top-left(Case 3) location. Results show that the distribution of LMA and LMR are different from each other, but both of them are closely related to the airflow pattern in the space. Results on overall room ventilation effectiveness are provided depending upon ventilation airflow rates for three different supply-exhaust configurations.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.582-587
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• 2011

Holdup characteristics of bubble, wake and continuous liquid phases were investigated in bubble columns with viscous liquid media. Effects of column diameter(0.051, 0.076, 0.102 and 0.152 m ID), gas velocity($U_G$=0.02~0.16 m/s) and liquid viscosity(${\mu}_L$=0.001~0.050 $Pa{\cdot}s$) of continuous liquid media on the holdups of bubble, wake and continuous liquid phases were discussed. The three phase such as bubble, wake and continuous liquid phases were classified successfully by adapting the dual electrical resistivity probe method. Compressed filtered air and water or aqueous solutions of CMC(Carboxy Methyl Cellulose) were used as a gas and a liquid phase, respectively. To detect the wake as well as bubble phases in the bubble column continuously, a data acquisition system(DT 2805 Lab Card) with personal computer was used. The analog signals obtained from the probe circuit were processed to produce the digital data, from which the wake phase was detected behind the multi-bubbles as well as single bubbles rising in the bubble columns. The holdup of bubble and wake phases decreased but that of continuous liquid media increased, with an increase in the column diameter or liquid viscosity. However, the holdup of bubble and wake phases increased but that of continuous media decreased with an increase in the gas velocity. The holdup ratio of wake to wake to bubble phase decreased with an increase in the column diameter or gas velocity, however, increased with an increase in the viscosity of con-tinuous liquid media. The holdups of bubble, wake and continuous liquid media could be correlated in terms of operating variables within this experimental conditions as: ${\varepsilon}_B=0.043D^{-0.18}U_G^{0.56}{\mu}_L^{-0.13}$, ${\varepsilon}_W=0.003D^{-0.85}U_G^{0.46}{\mu}_L^{-0.10}$, ${\varepsilon}_C=1.179D^{0.09}U_G^{-0.13}{\mu}_L^{0.04}$.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.922-930
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• 2004

An experimental investigation was performed to study on the generation of air bubble and air core with swirling flow in a horizontal cicular tube. To determine some characteristics of the flow, 2D PIV technique is employed for velocity measurement in water. The experimental rig is manufactured from an acryl tube. The test tube diameter of 80mm, and a length of 3000mm. The used algorithm is the gray leve cross-correlation method(Kimura et al. 1986). An Ar-ion laser is used and the light from the laser(500mW) passes through a probe to make two-dimensional light sheet. In order to make coded images of the tracer particles on one frame, an AOM(Acoustic-Optical Modulator) is used. The maximum axial velocities showed near the test tube wall at y/D =0.1 and y/D =0.9 along the test tube. The higher Reynolds number increase, the lower axial velocities are showed in the center of the test tube. The air bubbles are generated from Re =10,000 and developed into air core from the recirculating water pump rpm equal 30Hz. The pressure and temperature are measured across the test tube at X/D=3.33.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.112-119
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• 2000

A die-casting junction method is usually used to manufacture the tub of an IH(induction heating) jar. If there is a very small air bubble in the junction area, the thermal conductivity is deteriorated and local overheat occurs. Such problem brings serious inferiority of the IH jar. In this paper, we propose a new method to detect such defect with simply measured thermal data. Thermal distribution of preheated tubs is obtained by scanning with infrared thermal sensors and analyzed with the statistic pattern recognition method. By defining the characteristic feature as the temperature difference between sensors and using ellipsoid function as decision boundary, a supervised learning method of genetic algorithm is proposed to obtain the required parpameters. After applying the proposed method to experiment, we have proved that the rate of recognition is high even for a small number of data set.

• Journal of the Korean Arthroscopy Society
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• v.6 no.2
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• pp.126-130
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• 2002

Purpose : To evaluate the diagnostic efficiency of the subacromial bursoscopy with glenohumeral air infusion technique for detection of the full thickness tear which we used to think as a partial thickness tear, because it was hidden by bursal tissue. Materials and methods : We chose 65 cases and divided them into 2 groups. The group I was 18 cases with partial thickness rotator cuff tears on glenohumeral arthroscopic evaluation, and the group 2 was 37 cases with full thickness rotator cuff tears which were repaired. We inflated the glenohumeral Joint with 50-100ml of air and observed air bubble leakage simultaneously on bursoscopy. Results : In group I, we could detect air leakage in 3 cases and found that it was full thickness tear. In group II, 2 cases revealed too much air leakage proved that it was incomplete repair and was in need of additional suture. Conclusion : Air infusion technique is though to be a valuable method in differentiation between the partial and full thickness tear and for evaluation of the security of the repair.

• Journal of the Korea Society of Computer and Information
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• v.29 no.3
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• pp.91-98
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• 2024

In this paper, we present a particle-grid blending framework based on a geometric approach to efficiently represent opaque ice spheres with air bubbles. The water temperature is diffused through the grid and the air bubbles represented inside the ice through the particles. To solve the problem of previous methods that generate noisy dissolved air fields, we use levelsets to lighten the algorithm, i.e., the number of active particles and the initial amount of dissolved oxygen can be used to efficiently control the termination conditions of heat diffusion. We also extend the previous dissolved air field method, which only computes near air bubbles, to transparent regions to represent realistic ice spheres, and introduce a levelset-based approach to accurately compute the orientation of particles. As a result, the method presented in this paper is about three times faster than the existing methods and shows visually improved visualization of opaque ice spheres, which can be used in the field of representing physical virtual ice forms.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.595-601
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• 2001

We applied PIV method to obtain instantaneous and ensemble averaged velocity fields from the first row to the fifth row of a staggered tube bundle. The Reynolds number based on the tube diameter and the maximum velocity was set to be 4,000. Remarkably different natures are observed in the developing bundle flow. Such differences are depicted in the mean recirculating bubble length and the vorticity distributions. The jet-like flow seems to be a dominant feature after the second row and usually skew. However, the ensemble averaged fields show symmetric profiles and the flow characteristics between the third and fourth measuring planes are not so different. comparison between the PIV data and the RANS simulation yields severe disagreement in spite of the same Reynolds number. It can be explained that the distinct jet-like unsteady motions are not to be accounted in th steady numerical analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.11
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• pp.1031-1037
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• 2000

Isothermal vapor-liquid equilibrium(VLE) data have been obtained for the systems of propane(R290)+1,1,1,2-tetrafluoroethane(R134a) and 1,1,1,2-tetrafluoroethane(R134a)+isobutane(R60A) in the temperature range of 253.15 to 323.15K. Experiments were performed in a circulation type apparatus by injecting vapor through liquid pool using a magnetic pump. Both systems form azeotropes in the temperature range of this study. The experimental results were estimated with the Peng-Robinson equation of state. When the temperature-dependent binary interaction parameter was used in the Peng-Robinson equation of state, the absolute average deviation of the measured bubble point pressures from the values correlated by the Peng-Robinson equation was 0.65% and 0.78% for R290+R134a and R134a+600a, respectively. Azeotropic compositions for both systems were presented.

• Geotechnical Engineering
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• v.13 no.2
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• pp.39-54
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• 1997

Laboratory testings were carried out on plastic board drains (PBDs) using large scale test apparatus to evaluate the physical properties and the drainage performance. The test results reveal that the domestic products of PBDs are well compared with the foreign prod acts as far as the quality and drainage performance are concerned. It has also been confirmed that the discharge capacity decreases with time in such a way that the air bubbles are entrapped inside kinky PBDs and these air bubbles block the water flow through PBDs. It has been found that the vacuum pressure iseffectively applicable to recover the discharge capacity affected by the entrapped air bubbles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.186-191
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• 1999

The three speices of miroalgae (Chlorella vulgaris, Dunaliella salina and Porphyridium purpureum) were immobilized in Ca-alginate capsules as a basic study for development of economic cultivation process, and then were cultivated in an air-bubble column bioreactor. Under the batch culture of aerobic conditions, the thickness of the capsule membrane and $CO_2$ supply did not affect the growth of the immobilized microalga, Chlorella vulgaris. Cell concentration of immobilized microalgae in the capsule was higher than those of imobilized microalgae in beads and free cells. The cell concentration of microencapsulated Dunaliella salina was greater about 5 times than that of free cells. Based on these results, it is concluded that the application of microencapsulation technology to the culture of microalgae was an effective method for high-density cultivation.