• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.446-451
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• 2020

Flow induced vibration in a heat exchanger may cause damage to piping. The purpose of this study was to compare the characteristics of vortex shedding behavior through the circular tube banks at several tube locations, No.1, No. 10, and No. 19, with respect to time when the flow velocity of the inlet is constantly and periodically fluctuating.(60) The time characteristics of lift and the PSD characteristics were also investigated. In the case of periodic inlet flow velocity, strong vortex occurred at some time and after that time, a weak vortex was generated through the tube banks simultaneously. In the case of constant inlet flow velocity, the lift fluctuating frequency was 37.25Hz and that at the No. 19 tube was 18.63Hz and near 50Hz. In the case of periodic inlet flow velocity, the lift fluctuating frequency was 37.25Hz and 18.63Hz. The lift fluctuating frequency at No. 19 tube was observed broadly from 20Hz and 50Hz.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.1-8
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• 2016

When the oil is produced in the low temperature environment, wax can be accumulated in petroleum production system(pipeline, riser) and causes problems such as pipeline stucking, disturbance of the oil production. These problems can be lead to time-consuming and economic losses for flow assurance. For prediction and mitigation of wax deposition, it is necessary to measure the Wax Appearance Temperature(WAT) which is a temperature when the wax crystals start to be formed. WAT standard measurement method of transparent oil has to determine the cloud point of sample to the naked eye and cannot be applied to continuous change of the temperature. In this study, wax behavior of transparent oil samples are recorded depending on temperature using Visualized WAT Measurement System. Also, WATs of transparent oil samples are measured by image processing and compared with the result of the standard method.

• Fire Science and Engineering
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• v.17 no.4
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• pp.86-91
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• 2003

Since the air stream in the room controlled by HVAC system affects on he expected response of conventional detectors which are designed in accordance with normal characteristics of air stream in the fire incident, unexpected operation time delay may occur in fire. In order to solve this problem and to improve sensitivity so that to initiate fire in its early stages for minimizing damage and protecting people, we studied and developed Air Sampling Smoke Detector. The Air Sampling Smoke Detector is a kind of active-type fire detection system. it draws air continuously from the protected area through an air sampling pipe network to the smoke density analyzer. This study presents smoke density analysing technique and air intake balancing technique through an air sampling pipe network. As a result of evaluating, Air Sampling Smoke Detector was much more sensitive than conventional smoke detectors that passively wait for smoke to reach them and was not affected by ambient airflow in the room by means of balanced air intake through the sampling holes.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.195-202
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• 2016

In general, piston pumps are frequently used for concrete pumping. Filling coefficient signifies the ratio volume of a hydraulic cylinder to volume of concrete inside the cylinder. Therefore, it may be considered as a parameter directly affecting the flow rate and efficiency for concrete pumping. However, accurate analyses on this aspect have not yet been performed. In this paper, the data measured from horizontal pipeline pumping tests for 350m and 548m in length was analyzed to identify the relationships of rheological properties of concrete and stroke time with the filling coefficient. In addition, an equation allowing prediction of the filling coefficient from rheological properties of concrete and stroke time has been suggested.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.717-722
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• 2010

Supersonic/Hypersonic wind tunnel is a facility which is intended to test and to observe the physical phenomena around a model by creating supersonic flow in the test section. In designing an airplane, the wind tunnel test is demanded to analyzing aerodynamic characteristics of the model without making a prototype. In this research, the model aerodynamic facility(MAF) is modified for the purpose of increasing running time and its functionality. New pneumatic valves for remote control was installed for safety requirement, and new air tanks was installed on MAF as well. A pipe system is also modified to use those new valves and tanks, and the ceiling and side glasses of the test section are switched to ones with the larger surface area. After the MAF modification, a test is performed at Mach 2, 3 and 4. In this test, shadow graph technique, one of the flow visualization methods, is used to visualize supersonic flow field. The pressure in the settling chamber and working section at Mach 2, 3 and 4 was measured in each case. As a result, the possible model size and running time are obtained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.483-491
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• 2011

When pipe components made of carbon steel in nuclear, fossil, and industry are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the portion of pressure boundary. A study to identify the locations generating local wall thinning and to disclose turbulence coefficient related to the local wall thinning was performed. Experiment and numerical analyses for tee of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. To disclose the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.22-27
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• 2022

Atomic Layer Deposition (ALD) is a facility that deposits an atomic layer on a wafer by causing a chemical reaction after decomposition using heat or plasma by inputting two or more gases during the semiconductor process. The main gas used at this time is NH₃ (Ammonia). NH₃ has a relatively narrow explosive range with an upper limit (UFL) of 33.6% and a lower limit (LEL) of 15%, but it can explode if a large amount suddenly gathers in one place. It is Velocity and fatal if inhaled or in contact with the skin. NH₃ (Ammonia) of ALD (Atomic Layer Deposition) facility is supplied to the chamber through the gas inlet and discharged after the reaction.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.492-494
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• 2011

전력설비 증가와 더불어 GIS 사용이 확대되고 있는 상황에서 GIS 내부고장 발생시 복구 지연으로 인한 사례가 지속 발생하고 있다. 이를 예방하기 위해 170kV GIS 고장구간 판정시스템용 압력센서를 개발하고 검증을 위해 실사용 GIS 2대를 이용하여 내아크 시험을 수행한 결과이다. 시험을 통해 고장시 GIS 탱크 내부의 압력, 온도, 압력파를 측정하였고 SF6 Gas 배관과 연결된 현장조작함(LCP)내 가스주입구에 설치한 압력센서의 동작유무을 검증하였다. 시험결과 유동해석(CFD) 등 시뮬레이션 예측보다 압력 및 온도 상승이 높게 측정되었고 제품에 대한 신뢰성과 확대적용 가능성을 확인할 수 있었다.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.103-106
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• 2002

This paper presents an effective numerical method for analyzing three-dimensional unsteady conjugate heat transfer problems of a curved pipe subjected to infernally thermal stratification. In the present numerical analyses, the thermally stratified flows in the pipe are simulated using the standard $k-{\varepsilon}$turbulent model and the unsteady conjugate heat transfer is treated numerically with a simple and convenient numerical technique. The unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a non-staggered grid arrangement, SIMPLEC algorithm and higher-order bounded convection scheme. Numerical calculations have been performed far the two cases of thermally stratified pipe flows where the surging directions are opposite each other i.e. In-surge and out-surge. The results show that the present numerical analysis method is effective to solve the unsteady flow and conjugate heat transfer in a curved pipe subjected to infernally thermal stratification.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.391-397
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• 2002

Pressure drop were experimentally investigated for ice slurry flowing in the acrylic pipes with inner diameter of 24 mm. Ice slurry was made from 6.5% ethylene glycol-water solution, and the pipes is consisted of horizontal, vertical (upward and downward) and $90^{\circ}$ elbow pipe. The ice Packing factor (IPF) and the flow rate of the experiments were varied from 0 to 30% and from 5 to 70kg/min respectively The measured pressure drop in various pipe positions were compared with those for the solution flow (IPF=0). The pressure drop was larder than that for solution flows as the IPF increased when the flow rate was low or very high. Sharp increases in pressure drop were observed for the cases when IPF is more than 70% in horizontal and vertical pipes, whereas the pressure drop increased with the IPF simultaneously in an elbow pipe.