• Journal of computational fluids engineering
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• v.22 no.1
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• pp.1-7
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• 2017

The mixing of water and chemicals is an important process in the water purification plant. In this paper, we compare PDM(pump diffusion mixer) and hydraulic mixer at the basin in the mixing process. The proper flow rates are predicted and compared in both mixers using CFD technique. As a result, the flow rate of purifier chemical liquid should be 5% of that of water for the optimal performance of mixing process. The characteristics of the two mixing methods are compared with each other for strong and weak points on the operation of the purification system, discussed in the view point of CFD simulations.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.574-579
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• 2000

In this study. an off-design performance prediction program for centrifugal pumps is developed. To estimate the losses in an impeller flow passage, two-zone model and two-element in series(TEIS) model are used. At impeller exit. the mixing process occurs with an increase in entropy. In two-zone model. there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller was calculated by using TEIS model. While internal losses in an impeller an automatically estimated by using the above models, some empirical correlations far estimating external losses. far example, disk friction loss, recirculation loss and leakage loss are used. In order to analyze the vaneless diffuser flow. the momentum equations for the radial and tangential directions are used and solved together with continuity and energy equations.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.45-55
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• 1998

A theoretical and experimental study is performed to investigate the characteristics of ice slurry product. By diffusion-controlled evaporation model the possibility of ice slurry is theoretically anticipated. The water vapor evaporated from the surface of droplets is extracted continuously from the chamber by a vacuum pump. The droplet diameter is measured by silicon immersion method. The ice slurry is obtained by spraying droplets of ethylene glycol aqueous solution in the chamber where pressure is maintained under the triple point of water. The droplet with the diameter of 300 $\mu\textrm{m}$and the initial temperature of 2$0^{\circ}C$ was changed into ice particle within the chamber of 1.33m in height.

• Journal of Photoscience
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• v.6 no.3
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• pp.109-115
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• 1999

Intense excimer laser irradiation of polymer films results in expansion and the following contraction , recovering ithe initial flat surface. The morphological dynamics is meausred directly by nanosecond time-resolved interferometry for polystyrene(PS), polyurethane, and polyimide films. The expansion proceeds with a speed of a few nm/ns , while the contraction depends upon the polymer ; very low contraction for PS, rapid 2 component shrinking for polyurethane, and rapid monotonous decay for polymide. These characteristic behavior are considered from viewpoints of interpenetrating structures of polymers, glass-rubber phase transitioni, thermal diffusion, and photothermal mechanism.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.20-24
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• 2009

In order to explain the operating characteristics of LTMFP in a wide range of driving frequency, an analytical equation that takes into account the detailed behavior of the normal spot is necessary. In this paper, based on the phenomenon of magnetic diffusion of the superconductor we modified the theoretical equations for pumping action in LTMFP. The modified equations explained well the pumping actions under the different load magnets. These results are important to explain the pumping tendency of the LTMFP according to driving frequency.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.265-266
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• 2012

의료용 X-ray의 발전에 따라, 영상의 Digital화가 필요하게 되었다. Digital 영상 구현을 위해 다양한 형태의 영상 검출기가 개발되었다. 진단 영상의 조건으로는 구현 시간이 빠르고 해상도가 높아야 한다. 조건에 부합하는 Flat panel 형태의 직접방식과 간접방식 검출기의 개발이 주로 이루어졌으며, X-ray 검출 효율이 높고 공간 분해능이 높은 직접 방식의 검출기에 대한 연구가 활발히 진행되고 있다. 기존 직접방식의 X-ray 검출물질로는 A-Se이 이용되었다. 하지만 A-Se의 경우 낮은 원자번호로 인해 X-ray에 대한효율이 낮으며, 제조 공정과 수율의 문제로 인해 대체 물질의 개발과 공정의 개선이 필요하다. 선행 연구를 통해 X-ray 검출물질의 전기적 특성을 파악을 통해 대체 물질로서 가능성을 알아보았다. 본 연구에서는 기존에 제작된 X-ray 검출물질의 상부전극 증착 물질과 증착법 선정에 대한 연구이다. 선행 연구를 통해 선정된 X-ray 검출물질은 HgI2이다. 상, 하부 전극 선택에 있어 HgI2의 일함수 값(4.15eV)을 고려하여 그와 비슷한 일함수 값을 가진 물질로 전기적 장벽을 제거하여야 한다. 따라서, ITO (일함수 4.45eV)와 Au (일함수 5.1eV)을 선택하였다. ITO의 증착으로 이용된 방법으로는 on-axis 형태의 magnetron plasma sputtering을 이용하였으며, Au의 증착으로 이용된 방법은 Thermal evaporation deposition을 이용하였다. plasma sputtering에 이용된 타겟은 In2O3;SnO2 (조성비:90:10wt%)를 사용하였으며, Chamber의 크기는 넓이 456 ${\phi}cm^2$ 높이 25 cm이며, 로 target과 기판과의 거리는 15cm이다. plasma발생에 필요한 가스로는 Ar과 O2를 이용하였다. 고 진공 환경 조성에 이용된 장비로는 Rotary pump와 Turbo molecular pump이다. plasma 발생 전 진공도는 $3.2{\times}10^{-5}$ Torr, 발생 후 진공도는 $5.1{\times}10^{-5}$ Torr이다. plasma 환경이 조성된 후 증착 시간은 1분 30초이다. Au는 순도 99.999%를 이용하였으며, 이용된 금은 1회 증착에 0.3 g을 이용하였다. Chamber의 넓이 1,444 ${\phi}cm^2$이며, 높이 40 cm, boat와 기판과의 거리는 25 cm이다. 고 진공 환경 조성에 이용된 장비로는 Rotary pump와 diffusion pump를 이용하였다. Au의 승화 전 진공도는 $2.4{\times}10^{-5}$ Torr 증착 시 진공도는 $4.2{\times}10^{-5}$ Torr이며, Boat에 가해준 전압, 전류는 0.97 V, 47 A이며, 증착 시간은 1분 30초이다. 광도전체 층에 각각 증착된 전극의 저항을 통해 증착상태를 판단하였다. DMM (Digital Multimeter)로 1 cm 간격으로 측정된 표면의 저항은 ITO 약 $8{\Omega}$, Au 약 $3{\Omega}$으로 전극으로서 이용이 가능한 상태이다. Au와 ITO가 증착된 HgI2 시편의 전기적 특성은 기존에 이용된 X-ray 변환물질의 성능보다 우수하였다. 하지만 Au와 ITO가 각각 증착된 시편의 전기적 특성은 큰 차이를 보이지 않았다. ITO의 경우 진공 상태에서 이용되는 Gas가 이용되며, Plasma 환경 조성 유지가 어려운 점이 있다. Au전극은 증착 환경 조성이 쉽지만, 전극 물질 이용효율이 떨어지는 단점이 있다. 본 연구를 통해 X-ray 변환물질인 HgI2의 전극물질로 Au와 ITO의 이용가능성을 알아보았다. 두 전극으로 제작된 검출기의 성능은 큰 차이 없이 우수하였고, 전기적 장벽 상태가 낮아 높은 검출 효율을 보였다. 상대적으로 Au 전극의 공정이 간단하고 수율이 높다. 하지만 Au Source의 이용 효율이 떨어지는 단점이 있다. 본 연구의 결과를 통해 공정상의 유리함과 Source의 이용효율을 고려한 분석에 대한 연구가 필요할 것으로 사료된다.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4571-4584
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• 2022

The analysis of rapid flow transients in Reactor Coolant Pumps (RCP) is essential for a reactor safety study. An accurate and precise analysis of the RCP coastdown is necessary for the reactor design. The coastdown of RCP affects the coolant temperature and the colloidal crud in the primary coolant. A realistic and kinetic model has been used to investigate the behavior of activated colloidal crud in the primary coolant and steam generator that solves the pump speed analytically. The analytic solution of the non-dimensional flow rate has been determined by the energy ratio β. The kinetic energy of the coolant fluid and the kinetic energy stored in the rotating parts of a pump are two essential parameters in the form of β. Under normal operation, the pump's speed and moment of inertia are constant. However, in a coastdown situation, kinetic damping in the interval has been implemented. A dynamic model ACCP-SMART has been developed for System Integrated Modular and Advanced Reactor (SMART) to investigate the corrosion due to activated colloidal crud. The Fickian diffusion model has been implemented as the reference corrosion model for the constituent component of the primary loop of the SMART reactor. The activated colloidal crud activity in the primary coolant and steam generator of the SMART reactor has been studied for different equilibrium corrosion rates, linear increase in corrosion rate, and dynamic RCP coastdown situation energy ratio b. The coolant specific activity of SMART reactor equilibrium corrosion (4.0 mg s^-1) has been found 9.63×10^-3 µCi cm^-3, 3.53×10^-3 µC cm^-3, 2.39×10^-2 µC cm^-3, 8.10×10^-3 µC cm^-3, 6.77× 10^-3 µC cm^-3, 4.95×10^-4 µC cm^-3, 1.19×10^-3 µC cm^-3, and 7.87×10^-4 µC cm^-3 for ²⁴Na, ⁵⁴Mn, ⁵⁶Mn, ⁵⁹Fe, ⁵⁸Co, ⁶⁰Co, ⁹⁹Mo, and ⁵¹Cr which are 14.95%, 5.48%, 37.08%, 12.57%, 10.51%, 0.77%, 18.50%, and 0.12% respectively. For linear and exponential coastdown with a constant corrosion rate, the total coolant and steam generator activity approaches a higher saturation value than the normal values. The coolant and steam generator activity changes considerably with kinetic corrosion rate, equilibrium corrosion, growth of corrosion rate (ΔC/Δt), and RCP coastdown situations. The effect of the RCP coastdown on the specific activity of the steam generators is smeared by linearly rising corrosion rates, equilibrium corrosion, and rapid coasting down of the RCP. However, the time taken to reach the saturation activity is also influenced by the slope of corrosion rate, coastdown situation, equilibrium corrosion rate, and energy ratio β.

• Journal of the Korean Institute of Gas
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• v.21 no.6
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• pp.52-60
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• 2017

In diffusion process exhaust line during semiconductor manufacturing process, In order to improve the transportation efficiency in the piping by removing "The reaction by-product, $ZrO_2$ and The unreacted material, TEMAZ, TMA, $O_3$, etc" and "Powder being deposited", the piping temperature was raised to $80^{\circ}C$ or more by using the heater jacket, and the bellows at the rear end of the vacuum pump ruptured. So conducted a case study and try to prevent the similar accidents from occurring through case studies. The causes of the accident were analyzed as follows: the inflow of outside air due to the generation of a gap on the suction side of the vacuum pump and heating the pipe with the heater jacket resulted in the overpressure in the pipe due to the volumetric expansion of the gas generated by decomposition of the unreacted TEMAZ, It can be assumed that the most vulnerable bellows of the piping has been ruptured. In order to prevent such accidents, This study is aimed to identify the cause of pipeline rupture accident and to establish safety measures for the prevention of similar accidents by evaluating physical hazards of TEMAZ, which is assumed to be the cause of pipe rupture accident.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.15-20
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• 2008

Contaminated sediments are the actual cause for deterioration of coastal-ecosystem. So the developed countries have been in the process of making an effort to develop new techniques for monitoring and solving this problem since 1960. In this research, suction type pump dredging system of pilot size for collecting the filth from the seabed has been designed and manufactured that can prevent or minimize the secondary pollution by filth diffusion. For the practical use, the application possibility of the developed system has been checked through a system performance test. And, the evaluation of system performance according to the underwater body type has been carried out for system optimization by using CFD. The performance tests for checking the efficiency of sediment collecting system are done under two conditions i.e. when the system is non-operational and when the system is self-propelled. The results of this research showed the possibility of the development of dredging system to remove just the upper parts of filth from seabed.

• Journal of IKEEE
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• v.24 no.1
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• pp.59-66
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• 2020

In this study, the characteristics of ITO thin film was investigated to finding a low cost and highly transparent electrodes for display of mobile communication devices. The ITO film was deposited by DC magnetron sputter. The experimental conditions were changed as follows: 1. ambient pressure changed 1 to 3 mTorr with 1mTorr step, 2. bias electric voltage changed with 10V step. The chamber was pumped out by rotary pump until 10^-3Torr then the diffusion pump was used to lower the pressure of 10^-6Torr. The results shows us the film growth was obvious when the bias voltage was larger than 300V, but the overall thickness tendency was existed: the more voltage is the thicker thickness. At 330V bias voltage condition, the deposition rate was the largest and apparent grain was showed.