• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.835-840
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• 2000

The objective of the present study is to investigate the characteristics of pressure wave propagation of viscous fluid flow in a circular pipe line. The goal of this study is to select the best frequency of each control factor of a circular pipe. We intend to approach a formalized mathematical model by a very exact and reasonable polynomial for fluid transmission lines. and we computed this mathematical model by computer. The results show that the oil viscosity decreased as the length of the circular pipe increases. and The energy of pressure wave propagation decreased as the pipe diameter decreases. The factor is that density of oil was changed resonant frequency. It has been found the viscosity characteristics is changed largely by length of hydraulic pipe and volume of cavity tank.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2130-2135
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• 2007

Operating characteristics of a loop heat pipe (LHP) having a bypass line was investigated experimentally. The LHP had a sintered metal wick as a capillary structure and methanol as a working fluid. The sintered metal wick was made of stainless steel of which the average pore size was 5 ${\mu}m$and porosity of 47%. A bypass line of a small diameter was attached between the vapor escape passage and the liquid reservoir. The dimension of the flat evaporator was $50(L){\times}40(W){\times}30(H)$ mm and that of the condenser was $50(L){\times}40(W){\times}11(H)$ mm. Wall and pipe material of the LHP was stainless steel and heating area was 35(W) mm${\times}$35(L) mm. The inner diameters of vapor and liquid transport lines were 4.0 mm and 2.0 mm, and the lengths of the two lines were both 0.5 m. The LHP was tested for three different tilt angles of horizontal, favorite tilt, and adverse tilt. The thermal load range was up to 290 W at the condenser above evaporation position. Furthermore, the effect of a bypass line on the start-up transient as well as steady-state operation was presented and discussed.

• 대한기계학회논문집B
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• 제20권4호
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• pp.1449-1457
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• 1996

In this paper, the unsteady two dimensional model for the thermal stratification in the pressurizer surge line of PWR plant has been proposed to numerically investigate the heat transfer and flow characteristics. The dimensionless governing equations are solved by using the Control Volume Formulation and SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The temperature profile of fluids and pipe wall with time are shown when the thermal stratification occurs in the horizontal pipe. The numerical result shows that the maximum dimensionless temperature difference is about O.514 between hot and cold section of pipe wall at dimensionless time 1,632.

• 한국정밀공학회지
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• 제22권6호
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• pp.83-89
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• 2005

Most domestic fossil power plants have exceeded 100,000 hours of operation with the severe operating condition. Among the critical components of fossil power plant, high temperature steam pipe systems have had a many problems and damage from unstable displacement behavior because of frequent start up and shut down. In order to prevent the serious damage and failure of the critical pipe system in fossil power plants, 3-dimensional displacement measurement system was developed for the on-line monitoring. Displacement measurement system was developed with a use of a LVDT type sensor and two rotary encoder type sensors. This system was installed and operated on the real power plant successfully.

• Corrosion Science and Technology
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• 제15권4호
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• pp.182-188
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• 2016

Significant piping wall thinning caused by Flow-Accelerated Corrosion (FAC) and Erosion-Corrosion (EC) continues to occur, even after the Mihama Power Station unit 3 secondary pipe rupture in 2004, in which workers were seriously injured or died. Nuclear power plants in many countries have experienced FAC and EC-related cases in steam cycle piping systems. Korea has also experienced piping wall thinning cases including thinning in the downstream straight pipe of a check valve in a feedwater pump line, the downstream elbow of a control valve in a feedwater flow control line, and failure of the straight pipe downstream of an orifice in an auxiliary steam return line. Cause analyses were performed by reviewing thickness data using Ultrasonic Techniques (UT) and, Scanning Electron Microscope (SEM) images for the failed pipe, and numerical simulation results for FAC and EC cases in Korea Nuclear Power Plants. It was concluded that the main cause of wall thinning for the downstream pipe of a check valve is FAC caused by water vortex flow due to the internal flow shape of a check valve, the main cause of wall thinning for the downstream elbow of a control valve is FAC caused by a thickness difference with the upstream pipe, and the main cause of wall thinning for the downstream pipe of an orifice is FAC and EC caused by liquid droplets and vortex flow. In order to investigate more cases, additional analyses were performed with the review of a lot of thickness data for inspected pipes. The results showed that pipe wall thinning was also affected by the operating condition of upstream equipment. Management of FAC and EC based on these cases will focus on the downstream piping of abnormal or unusual operated equipment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.88.3-88
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• 2001

In this paper, an on-line multi-sensor visual inspection technique for seamless steel pipe´s straightness is developed. The basic principle of the visual measuring method is detailed. The modeling of visual sensor, measurement system and data processing are presented. In order to test the accuracy of the multi-sensor visual inspection, an experiment inspecting the straightness of a 1500mm long seamless steel pipe is made. The experiment results show that the visual inspection technique can achieve on-line measurement and offers high precision and stability.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.499-503
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• 2002

This work focuses on eliminating tiny particles from the coolant in a nuclear pipe line by using a permanent magnet on the exterior surface of the pipe. This method have some merits compared with the many applied methods and is expected to be applied to most of the pipe lines in the nuclear plant. For instance in this method, a ring is attached to the exterior surface of the pipe, so that it does not affect the inflows directly. Further, the cost needed in the initial build-up of the facility is low.

• 기술사
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• 제15권1호
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• pp.7-13
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• 1982

지하통신용 케이블 보호용 관로로 사용되는 합성수지관의 안전수행문제는 점차 중요성이 인식되어지고 있어 이를 검토하기 위하여 유형별에 의한 역학적 실험을 실시하였다. 그 결과 본 연구에서는 매설 파이프가 받는 토압과 수압을 실험치와 이론치로 서로 비교하여 보았고 매설깊이 별에 의한 총압력을 계산하여 적정한 매설 보건을 추정하였으며 또한 재료 특성을 파악하여 충격효과 및 변형에 대한 두께와의 관계를 알았다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1198-1205
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• 2003

Most domestic fossil power plant have exceeded 100,000 hours of operation with the severe operating condition. Among the critical components of fossil power plant, high temperature steam pipe system have had a many problems and damage from unstable displacement behavior because of frequent start up and shut down. In order to prevent the serious damage and failure of the critical pipe system in fossil power plant, 3-dimensional displacement measurement system were developed for the on-line monitoring system. 3-D Measurement system was developed with using the LVDT type sensor and rotary encoder type sensor, this system was installed and operated on the real power plant successfully. In the future time, network system of on-line diagnosis for critical pipe will be designed.

• 대한기계학회논문집
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• 제15권2호
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• pp.693-702
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• 1991

The existence of residual stress in the circumferential butt welded pipes is one of the most important problems concerning stress corrosion cracking in service. In this paper, the residual stress distributions in three kinds of circumferential butt welded pipes were measured by the hole drilling strain gage method and calculation using finite element method is performed and its results are compared with the experiments. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed rom compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self restraint bending force in the pipe welding.