• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2053-2065
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• 2003

The current trend in automotive finishing industry is to use more electrostatic rotating bell (ESRB) need space to their higher transfer efficiency. The flow physics related with the transfer efficiency is strongly influenced by operating parameters. In order to improve their high transfer efficiency without compromising the coating quality, a better understanding is necessary to the ESRB application of metallic basecoat painting for the automobile exterior. This paper presents the results from experimental investigation of the ESRB spray to apply water-borne painting. The visualization, the droplet size, and velocity measurements of the spray flow were conducted under the operating conditions such as liquid flow rate, shaping airflow rate, bell rotational speed, and electrostatic voltage setting. The optical techniques used in here were a microscopic and light sheet visualization by a copper vapor laser, and a phase Doppler particle analyzer (PDPA) system. Water was used as paint surrogate for simplicity. The results show that the bell rotating speed is the most important influencing parameter for atomization processes. Liquid flow rate and shaping airflow rate significantly influence the spray structure. Based on the microscopic visualization, the atomization process occurs in ligament breakup mode, which is one of three atomization modes in rotating atomizer. In the spray transport zone, droplets tend to distribute according to size with the larger drops on the outer periphery of spray. In addition, the results of present study provide detailed information on the paint spray structure and transfer processes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.238-246
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• 2004

This paper reports an experimental study around a module about forced air flow by blower (35${\times}$35${\times}$6㎣) in a portable personal computer model(200${\times}$235${\times}$10㎣). Experimental report is to know three data to investigate thermal resistance, adiabatic wall temperature and visualized fluid flow around the module by combination of the moving number and the arrangement method of blower. The channel inlet flow velocity has been varied between 0.26, 0.52 and 0.78㎧, and input power ( $Q_{p}$) to the module is 4W. To investigate thermal resistance. the heated module is mounted on two boards(110${\times}$110${\times}$1.2㎣, k=20.73, 0.494W/ $m^{\circ}C$) in parallel-plate channel to forced air flow. The temperature distribution were visualized by heated module on acrylic board(k=0.262W/ $m^{\circ}C$) using liquid crystal film. Fluid flow around the module were visualized using particle image velocimetry system.

• Korea-Australia Rheology Journal
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• v.18 no.3
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• pp.153-160
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• 2006

We analyzed the non-Newtonian and non-isothermal flow with Carreau-Yasuda viscosity model in co-rotating and counter-rotating twin screw extruder systems. The mixing performances with respect to the screw speed, the screw pitch, and the rotating direction have been investigated. The dynamics of mixing was studied numerically by tracking the motions of particles. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the average strain. The results showed that the high screw speed decreases the residence time but increases the deformation rate. Small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance, while the small screw pitch increases the distributive mixing performance. Co-rotating screw extruder has the better conveying performance and the distributive mixing performance than counter-rotating screw extruder with the same screw speed and pitch. Co-rotating screw extruder developed faster transport velocity and it is advantageous the flow characteristics to the mixing that transfers polymer melt from one barrel to the other barrel.

• Journal of Industrial Technology
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• v.3
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• pp.17-26
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• 1983

The blast vibrations were measured from 10 places through Seoul subway area to study their effects on the structures and to establish the safe blasting limits. For purpose of the present study, particle velocity only was recorded and analyzed, because it correlated most directly with damage. The results are as follows: (1) The proagation equation, $V=K(D/W^{1/3})^{-n}$ was obtained. Typical values could be found for n range from 1.7 to 1.5 and for k range from 48 to 138. (2) From the relationship between schmidt hammer rebound hardness and uniaxial compressive strength, $Sc=0.514{\times}(S.H)^{0.23}$, the compressive strength at any area can be assumed. (3) The use of AN-FO and other explosives with low detonation pressure may reduce vibration levels generated.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.216-220
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• 2014

This paper presents effect of nozzle hole number on atomization characteristic of DME fuel spray using three different type of injector having the hole number of 6, 7 and 8. For this study, PDPA(phase Doppler particle analyzer) experiment was performed in terms of $T_{ASOE}$ under various injection pressure. To compare general trend of atomization characteristic, the law data were ensemble averaged based on $T_{eng}$ of 0.2 ms. Results showed that the droplet diameter in terms of SMD(Sauter Mean Diameter) was reduced as increase in injection pressure. Increasing the number of hole lead to reduce in droplet diameter, but no significant reduction in diameter was observed between hole number of 7 and that of 8. In addition, increasing the number of hole resulted in decrease in droplet velocity which is considered as the effect of reduction in spray momentum due to decreasing of fuel quantity per each hole.

• Explosives and Blasting
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• v.23 no.1
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• pp.19-30
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• 2005

In this study, the standard particle velocity equations and the equation for calculating specific charge weight with application of rock fracture method using the finecker plus are suggested and the existing equation of fragmentation was transformed into one applicable to finecker plus. Standard rock fracture pattern was designed. Square root scaled equation is $V=345.39(D/\sqrt{W})^{-1.4484$. computable equation to specific charge wei인t is $W_f=(2.3\~2.5)\;f_agdV$, charge weight per hole is 0.54kg, and proportion of diameter 30cm fragmentation is about $48.7\%$. This rock fracture method nay him out to be more excellent than the other methods.

• Journal of the Korean Society of Visualization
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• v.10 no.3
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• pp.30-36
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• 2012

We are planning to construct a scaled-down moderator facility to simulate the CANDU-6 moderator circulation phenomena during steady state operating and accident conditions. In the present work a preliminary experiment using a 1/40 scaled-down moderator tank has been performed to investigate the anticipated problems of the flow visualization and measurement in the planning scaled-down moderator facility. We shortly describe CFD analysis result for the 1/40 scaled-down test model and the flow measurement techniques used for this test facility under isothermal flow conditions. The Particle Image Velocimetry (PIV) method is used to visualize and measure the velocity field of water in a transparent Plexiglas tank. Planar Laser Induced Fluorescence (PLIF) technique is used to evaluate the feasibility of temperature field measurement in the range of $20-40^{\circ}C$ of water temperature using an one-color method.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.53.3-54
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• 2018

Solar Proton Events (SPEs) are the energetic phenomena related particle acceleration occurred in solar corona. Conventionally, they have been classified into two groups as the impulsive and gradual cases caused by reconnection in the flaring site and by shock generated by CME, respectively. In the previous studies, we classified these into four groups by analyzing the proton acceleration patterns in multi-energy channel observation. This showed that acceleration due to the magnetic reconnection may occur in the corona region relatively higher than the flaring site. In this study, we analyzes 54 SPEs observed in the energy band over 25 MeV from 2009 to 2013, where STEREO observations as well as SOHO can be utilized. From the multi-positional observation, we determine the exact time at which the Sun-Earth magnetic field line meets the CME shock structure by considering 3-dimensional structure of CME. Also, we determine the path length by considering the solar wind velocity for each event, so that the SPE onset time near the sun is obtained more accurately. Based on this study, we can get a more understanding of the correlation between CME progression and proton acceleration in the solar coronal region.

• Journal of Industrial Technology
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• v.6
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• pp.19-31
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• 1986

The residence time distribution of liquid flow in a 4.0cm diameter column packed with porous $Al_2O_3$ spheres of 0.37cm diameter were measured with pulse injections of a tracer under cocurrent trickling flow conditions. The mean residence time of liquid flow and liquid hold-up calculated by the transient curve of tracer were unaffected by gas flow rates under experimental ranges of liquid flow rates from 2.4 to $4.5(kg/m^2\;sec)$ and gas flow rates from 0 to $0.13(kg/m^2\;sec)$. The axial dispersion coefficient of liquid stream and apparent diffusivity of tracer in a micropore of solid particle were estimated from the response curve of tracer. The calculated Peclet No. were increased in ranges of 68-to 82 with a increasing of liquid mass velocity, and the external effective contacting efficiency between liquid and solid which can be expressed. by $(D_i)_{app}/D_i$ varied in ranges of 0.54 to 0.68 depending on the liquid flow rates. The gas to liquid(water) volumetric mass transfer coefficient were determined from desorption experiments with oxygen at $25^{\circ}C$ and 1 atm. The measured mass transfer coefficients were increased with liquid flow rates and the effect of gas flow rates on the mass transfer coefficient was insignificant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3620-3629
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• 1996

In the free molecular flow range, the pumping performance of a turbomolecular pump has been predicted by calculation of the transmission probability which employs the integral method and the test particle Monte-Carlo method. Also, new approximate method combining the double stage solutions, so called double-approximation, is presented here. The calculated values of transmission probability for the single stage agree quantitatively with the previous known numerical results. For a six-stage pump, the Monte-Carlo method is employed to calculate the overall transmission probability for the entire set of blade rows. When the results of the approximate method combining the single stage solutions are compared with those of the Monte-Carlo method at dimensionless blade velocity ratio C=0.4, the previous known approximate method overestimates as much as 34% than does the Monte-Carlo method. But, the new approximate method gives more accurate results, whose relative error is 10% compared to the Monte-Carlo method, than does the previous approximate method.