• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.4
• /
• pp.437-442
• /
• 2010

Flow-accelerated corrosion (FAC) leads to thinning of steel pipe walls that are exposed to flowing water or wet steam. From experience, it is seen that FAC damage to piping at fossil and nuclear plants can result in outages that require expensive repairs and can affect plant reliability and safety. CHECWORKS have been utilized in domestic nuclear plants as a predictive tool to assist FAC engineers in planning inspections and evaluating the inspection data so that piping failures caused by FAC can be prevented. However, CHECWORKS may be occasionally ignore local susceptible portions when predicting FAC damage in a group of pipelines after constructing a database for all the secondary side piping in nuclear plants. This paper describes the methodologies that can complement CHECWORKS and the verifications of CHECWORKS prediction results using numerical analysis. FAC susceptible locations determined using CHECWORKS for two pipeline groups of a nuclear plant was compared with determined using the numerical-analysis-based FLUENT.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.1
• /
• pp.112-121
• /
• 2024

The pipping system is widely used in many industries as equipment for transporting fluids over long distances. In high-pressure pipe, as the speed of the fluid increases, a loud noise is generated. Therefore, various studies have been conducted to reduce pipe noise. In this paper, a pipe noise analysis was developed to predict and quantitatively assess the flow-induced vibration and acoustic-induced vibration due to valve flow in high-temperature and high-pressure. To do this, a high-fidelity fluid analysis technique was developed for predicting internal flow in the pipe with valve. In additional, the contribution of compressible/incompressible pressure by frequency band was evaluated using the wavenumber-frequency analysis. To predict a low/middle frequency pipe noise, the vibroacoustic analysis method was developed based on Finite Element Method (FEM). And the pipe noise prediction method for the middle/high frequency was developed based on Statistical Energy Analysis (SEA).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.4
• /
• pp.429-435
• /
• 2010

In approximately fifty utilities, including KHNP (Korea Hydro & Nuclear Power), CHECWORKS is used as a tool for predicting and managing the wall thinning of carbon steel piping; this wall thinning is caused by flow-accelerated corrosion (FAC). It is known that CHECWORKS is only applicable to predict the wall thinning of piping with large bores. When dealing with small-bore steel piping, FAC engineers measure the thickness of the susceptible area that is selected on the basis of the experience and judgment of the engineer. This paper proposes the application of CHECWORKS for the management of wall thinning of small-bore piping. Four small-bore pipelines of a domestic nuclear power plant were analyzed from the viewpoints of FAC and fluid dynamics by using CHECWORKS and FLUENT code. Depending on the engineer's skill, CHECWORKS can also be used for the management of wall thinning of small-bore piping.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.103.1-103.1
• /
• 2005

• Journal of the Korean Institute of Gas
• /
• v.4 no.2 s.10
• /
• pp.7-14
• /
• 2000

LNG (Liquified Natural Gas) carried by LNG ship is unloaded into the LNG storage tanks at the very low temperature (a little lower than the boiling point of LNG). Because LNG is unloaded through the pipeline, two phase flow appears in the pipeline. In this study, we have studied the pressure-drop mechanisms of the two-phase flow in the pipeline, and the calculation method of BOG (Boil-off Gas) amount based on the heat transfer mechanism through the insulation and the surface of the pipeline. We have developed a computer program for thermal-hydraulic analysis on the LNG pipeline system. We have also developed the optimal design program to find the optimal thickness of insulation and the pipeline size. The program searches the optimal design with the minimum capital cost of pipelines and insulation on the operating conditions of maximum allowance pressure-drop and BOG amount, etc.

• Journal of the Korean Institute of Gas
• /
• v.10 no.3 s.32
• /
• pp.7-12
• /
• 2006

In this paper, a new evaluation scheme is suggested to estimate load-carrying capacities of wall thinned pipes. At first, computational fluid dynamics analyses employing steady-state and incompressible flow are carried out to determine pressure distributions in accordance with conveying fluid. Then, the variational pressures are applied as input condition of structural finite element analyses to calculate local stresses at the deepest point. The efficiency of proposed scheme was proven from comparison to conventional analyses results and it is recommended to consider the fluid structure interaction effect for exact integrity evaluation.

• Korean Chemical Engineering Research
• /
• v.57 no.5
• /
• pp.628-636
• /
• 2019

In various industrial processes, piping serves as a link between unit processes and is an essential installation for internal flow. Therefore, the optimum design of the piping system is very important in terms of safety and cost, which requires the estimation of the pressure drop, flow rate, pipe size, etc. in the piping system. In this study, we developed a software that determines pressure drop, flow rate, and pipe size when any two of these design variables are known. We categorized the flows into single phase, homogeneous two phase, and separated two phase flows, and applied suitable calculation models accordingly. We also constructed a system library for the calculation of the pipe material, relative roughness, fluid property, and friction coefficients to minimize user input. We further created a costing library according to the piping material for the calculation of the investment cost of the pipe per unit length. We implemented all these functions in an integrated environment using a graphical user interface for user convenience, and C # programming language. Finally, we verified the accuracy of the software using literature data and examples from an industrial process with obtained deviations of 1% and 8.8% for the single phase and two-phase models.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.1 no.1
• /
• pp.55-63
• /
• 1997

The empirical factor and reaction force based on published data were involved to investigate compressible flows through sudden enlargement and sudden contraction passages. Analytical solutions of engineering interest were obtained from one-dimensional steady compressible gas dynamic equations. The effects of com- pressibility, cross-sectional area ratio, and inlet Mach number on the air flows were discussed with regards to the total pressure loss and flow choking. The present results provide available information necessary to design the compressible pipe flow systems.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1998.04a
• /
• pp.19-19
• /
• 1998

최근 화학, 연소, 동력, 제철 등의 각종 플랜트에서 조업압력이 고압화되어 가고 있으며, 이에 수반하여 배관계를 통하는 고압가스 유동에 관한 연구가 활발하게 진행되고 있다. 배관계를 통하는 고압가스의 유동에 있어서 유량의 적절한 제어, 유동에 의하여 야기되는 배관계의 소음·진동, 그리고 배기가스의 적절한 처리법 등은 공학적으로 매우 중요한 문제로 알려져 왔다. 일반적으로 정상운전을 하는 플랜트에서 고압 배기가스의 문제는 배기가스 Expander에 의하여 에너지를 회수하는 방법이 생각될 수 있으나, 실제 공업현장에서는 배기가스를 안전하고, 또 소음·진동을 발생시키지 않도록 적절하게 처리하는 것이 매우 중요한 기술적 과제로 남아 있다. 일반적으로 배기가스의 압력이 임계압력(critical pressure) 이상으로 되는 경우(실제 대부분의 플랜트에서 배기가스의 압력은 임계압력보다 매우 높다), 배관계 내부에서 충격파(shock-wave)가 발생하여 난류와동 혹은 난류경계층과 간섭하게 됨으로써 강력한 공기역학적 소음이나 진동을 발생시키게 된다. 이와 같은 소음·진동에 대한 대책으로는 현재 가스배출부에 감압밸브를 직렬로 설치하거나, 유로에 다공판(porous plates)들을 삽입하여 감압과정을 공간적으로 분산시킴으로써, 충격파가 발생하지 않도록 하는 방법을 주로 채택하고 있다. 그러나 이러한 방법을 적용하는 경우 배기가스 유동에 대한 유량의 제어기능이 저하되는 문제가 발생한다.

• Journal of the Society of Disaster Information
• /
• v.18 no.3
• /
• pp.550-559
• /
• 2022

Purpose: Pipes are widely used as applied devices in many industrial fields such as machinery, electronics, electricity, and plants, and are also widely used in safety-related fields such as firefighting and chemistry. With the diversification of products, the importance of technology in the piping field is also increasing. In particular, when changing the existing copper pipe to stainless steel, it is necessary to evaluate safety and flow characteristics through structural analysis or flow analysis. Method: This study investigated the safety by flow analysis of the 6.35 inch socket model, which are integrated insert type connectors developed by a company, using CFD analysis technique. For CDF analysis, RAN model and LES model are used. Result: As results of the analysis, amplitude of the pressure fluctuation acting on the wall of the piping system is formed at a level of 3,780 Pa or less, which is a very small level of pressure compared with the operating pressure or design stress of the refrigerant piping. Conclusion: These results mean that the effect of vibration caused by turbulence on the structural safety of the pipe is negligible.