• 플랜트 저널
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• 제8권2호
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• pp.52-58
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• 2012

Pipe means the connection of the tube in order to transfer fluid from one device to another device. The piping stress analysis is to analyze the structural stability considering the location and the features of piping support after completing the piping design, The allowable stresses comply with the requirements of the relevant standards by examining whether the support of the function and location of pipe or re-operation is confirmed. Allowable stresses are to make sure that the maximum stress should not exceed the allowable stress presented in the ASME B31.1 POWER PIPING code. ASME B31.1 POWER PIPING code ensures a smooth stress analysis can be performed during the initial pipe stress analysis as provided in the case of straight pipe to the horizontal distance between the supports. However, because there is no criteria set in the case of curved pipe, the optimum pipe supporting points were studied in this paper. As mentioned about the curved pipe, loads applied to the support of the position of 17% and 83% of the position relative to the elbow part have results similar to the load acting on the support of straight pipe.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.474-481
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• 2001

This paper addresses a numerical method for predicting transient temperature distributions in the wall of a curved pipe subjected to internally thermal stratification flow. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in the non-orthogonal coordinate systems is presented. The proposed method is implemented in a finite volume thermal-hydraulic computer code based on a cell-centered, non-staggered grid arrangement, the SIMPLEC algorithm, a higher-order bounded convection scheme, and the modified version of momentum interpolation method. Calculations are performed for the transient evolution of thermal stratification in two curved pipes, where the one has thick wall and the other has so thin wall that its presence can be negligible in the heat transfer analysis. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a finite wall thickness can be satisfactorily analyzed by the present numerical method, and that the neglect of wall thickness in the prediction of pipe wall temperature distributions can provide unacceptably distorted results.

• 한국전산유체공학회지
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• 제7권3호
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• pp.35-43
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• 2002

This paper addresses a numerical method for predicting transient temperature distributions in the wall of a curved pipe subjected to internal laminar thermally-stratified flow. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in non-orthogonal coordinate systems is presented. Numerical calculations are performed for the transient evolution of thermal stratification in two curved pipes, where one has thick wall and the other has so thin wall that its presence can be negligible in the heat transfer analysis. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a finite wall thickness can be satisfactorily analyzed by the present numerical method, and that the neglect of wall thickness in the prediction of pipe wall temperature distributions can provide unacceptably distorted results for the cases of pipes with thick wall such as safety related-piping systems of nuclear power plant.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1173-1178
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• 2007

The robot for narrow space is used in searching, investigating or cleaning. Up to now variety of researches on in-pipe robots have been introduced. However it is still hard to overcome vertical or curved passage. In most cases of narrow space robots are able to travel just aimed diameter which was selected when those are developed. Also, a large percentage of robots are not able to detect the configuration of pipe or circumstance. In this paper we present a robot called PAROYSⅡ for narrow space with vertical and curved passage. This proposed robot is not affected at all to variance of pipes, vertical or horizontal passages, curved pipes, projecting parts and parallel planes. In addition to that, it will perceive the internal configuration of pipe and terrain, which will be not only available to control navigating scheme by itself, but also mappable about the passage which the robot traveled. Core points in the design and structure are introduced and preliminary verification is given.

• 소음진동
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• 제7권3호
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• pp.489-498
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• 1997

In this paper, chaotic motions of a curved pipe conveying oscillatory flow are theoretically investigated. The nonliear partial differential equation of motion is derived by Newton's method. The transformed nonlinear ordinary differential equation is a type of Hill's equation, which has the external and parametric excitation with a same frequency. Bifurcation curves of chaotic motion of the piping systems are obtained by applying Melnikov's method. Numerical simulations are performed to demonstrate theoretical results and show the strange attractor of the chaotic motion.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.649-654
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• 2000

The non-linear differential equations of motion of a fluid conveying curved pipe are derived by making use of Hamiltonian approach. The extensible dynamics of the pipe is based on the Euler-Bernoulli beam theory. Some significant differences between linear and nonlinear equations and the basic analysis results are discussed. Using eigenfrequency analysis, it can be shown that the natural frequencies are changed with flow velocity.

• Nuclear Engineering and Technology
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• 제41권3호
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• pp.287-294
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• 2009

Due to thermal hydraulics phenomena, such as thermal stratification, various events occur to the parts of a nuclear power plant during their lifetimes: e.g. cracked and dislocated pipes and thermally fatigued, bent, and damaged supports. Due to the operational characteristics of the parts of the steam generator feedwater inlet horizontal pipe, thermal stratification takes place particularly frequently. However, the thermal stress due to thermal stratification at the steam generator feedwater inlet horizontal pipe was not reflected in the design stage of old plants(Kori Unit No.1, 2, 3 and 4, Yeonggwang Unit No. 1 and 2, and Uljin Unit No. 1 and 2; referred to as old-style power plants hereinafter). Accordingly, a verification experiment was performed for thermal stratification in the horizontal inlet nozzle steam generator of old-style plants. If thermal stratification occurred in the horizontal pipe of an old-style power plant, numerical analysis of the temperature distribution of the pipes and fluids was conducted. The temperature distributions were compared at the curved part of the pipe and the horizontal pipe before and after the installation of the improved thermal sleeves designed to alleviate thermal stress due to thermal stratification. The thermal stress reduction measure was proven effective at the steam generator inlet horizontal pipe and the curved part of the pipe.

• 한국유체기계학회 논문집
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• 제13권3호
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• pp.54-58
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• 2010

The pneumatic waste collection system, which is a complete solution for solving the waste collection problems, are constructed in many countries all over the world. However, research data for piping network design are insufficient. In this paper the pressure losses of the straight and curved pipes, pipe junctions are obtained using the numerical method in order to investigate the optimal pipe network design for the waste collection system. As an experimental result, the length of 1.8 meter is the reasonable for the radius of curvature of a curved pipe and the angle of 30 degree is suitable for confluent pipe.

• 한국해양공학회지
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• 제27권2호
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• pp.13-18
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• 2013

Most ships and offshore structures are equipped with a variety of pipes, which inevitably contain curved portions. The structural design of these pipes mostly relies on the commercial code, CAESAR-II, which was especially developed for the structural analysis of pipes. This study conducted stress analyses of the same pipe unit, including loops, using both CAESAR-II and MSC/NASTRAN, and compared the results to investigate the characteristics of CAESAR-II. A parametric study was then conducted of the various design variables of pipe loops using CAESAR-II to draw some useful information about the structural characteristics of the loops.

• 한국시뮬레이션학회논문지
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• 제7권2호
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• pp.115-123
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• 1998

A simulation is performed to investigate the effect of the pipe supports on the change of the natural frequencies of curved pipe systems containing fluid flow, for different elbow angles and geometry of the pipe systems. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the corresponding eigenvalue problem. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies. Without any support, the change of the fundamental natural frequency due to the geometric change is smaller than the change of the second or higher natural frequencies. The more curve parts exist in the pipe system, the less change of lower frequency range, compared with the change of higher frequency range, is observed. Spring supports can be used to reduce the fundamental natural frequency, without change of the second or higher natural frequencies. To avoid resonance, which is critically dangerous from the view point of structural dynamics, the mechanical properties such as stiffness or the location of pipe supports are need to be changed to isolate the natural frequencies from the frequency range of dominant vibration modes.