• Proceedings of the KWS Conference
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• 2006.10a
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• pp.292-294
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• 2006

Many processes have been introduced to join PE pipes, but most of these methods have lots of disadvantages such as costs and lack of reliability, etc. Recently due to the benefits of cost, safety and reliability, the butt welding has been paid much attention to joint PE pipes. In case of butt welding, the heat plate which is used to melt PE pipes is the most critical equipment. In this study, after developing the heat plate of new shape, the PE double wall pipes with misalignments were butt-welded by using the conventional and developed heat plates and comparison of weld-zones and tensile test was performed. As the results of tensile test, weld-zones using developed heat plate have strength of $147.7{\sim}251.0%$ of weld-zones using conventional heat plate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.385-390
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• 2002

To clarify the hydraulic characteristics of ice slurry which made from 6.5% ethylene glycol-water solution flowing through circular pipes of small diameter, experimental studies were performed. The flow pattern was observed and the pressure drop was measured in acrylic pipes with inner diameter of 24 mm. The results of flow visualization revealed that ice particles flowed along the top of pipes in the ranges of small ice fraction and low flow rate, while Ice particles diffused into the whole region of pipes flowed like a homogeneous flow for high flow rate and high ice fraction. An increase in frictional pressure drop was measured as the ice fraction increased in all pipes and unstable flow was observed for up-ward vertical pipe.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.6-12
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• 2011

The failure probabilities of pipes in nuclear power plants due to stress corrosion are obtained using the P-PIE program, which is developed for evaluating failure probability of pipes based on the existing PRAISE program. Leak, big leak and LOCA(loss of coolant accident) probabilities are calculated as a function of operating time for several pipes in a domestic nuclear plant. The sensitivity analysis is also performed to find out the important parameters for the failure of pipes due to stress corrosion. The results show that the steady state oxygen concentration and steady state temperature are important parameters and failure probability is very low when the oxygen concentration is maintained according to the regulation.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.305-310
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• 2008

This paper provides the methods to estimate the burst pressures of the pipes with defects, based on finite element analyses. FE codes are frequently adopted for the simulations of the burst tests of the pipes with defects. However, those do not give the burst pressure directly. Because the post-processing should be followed; determination of the fracture strains in accordance with triaxialities, monitoring the strains of pipes, etc. In the present work, these efforts are implemented in the user subroutine UHARD within the general-purpose FE code, ABAQUS. Four fracture criterions are introduced to estimate the burst pressure of pipes, and a simple fracture strain estimate is also developed. FE analyses for the pipe with gouge and corrosion are performed, and the results are compared with the experiment results.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.292-297
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• 2001

One of the major characteristics that affects the life of welded steel water pipes is the stress distribution caused by welding and external forces. Some studios have bean carried out on the residual stress of steel water pipes. But the results on the stress distributions by welding and complex external forces are rare, because real water pipes operate under the ground and many kinds of external forces act simultaneously on the joints. To understand the complex stress distributions of welded joints, therefore predictions by numerical or analytic methods are required. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Based on these results, stress distributions by welding and complex external forces are evaluated by adopting the same numerical method. The influence of some post weld heat treatments on residual stress distributions is also investigated.

• Nuclear Engineering and Technology
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• v.32 no.1
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• pp.67-76
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• 2000

Significant wall thinning due to flow accelerated corrosion(FAC）was recently reported in main feedwater pipes in 3 Korean pressurized water reactor(PWR) plants. The main feedwater pipes in one plant were repaired using overlay weld method at the outside of pipe, while those in 2 other plants were replaced with new pipes. In this study, the effect of the wall thinning in the main feedwater pipes on piping integrity was evaluated using finite element method. Especially, the effects of both the overlay weld repair and the stress concentration in notch-type thinned area on the piping integrity were investigated. The results are as follows : (1) The piping load carrying capacity may significantly decrease due to FAC. In special, the load carrying capacity of the main feedwater pipe was reduced by about 40% during about 140 months operation in Korean PWR plants. (2) By performing overlay weld repair at the outside of pipe, the piping load carrying capacity can increase and the stress concentration level in the thinned area can be reduced.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.871-879
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• 2002

The characteristics of flow and heat transfer in the heat exchanger of heat pipes with fins have been studied numerically for cooling enhancement of electronic components of KTX (Korea Train eXpress). Numerical analysis and methodology have been conformed by comparing the experimental results for inlined array of heat pipes. The staggered arrangement of heat pipes has been proposed in order to achieve heat transfer enhancement. As results, the geometry change to the staggered array is conformed to increase the heat transfer of the system accompanied by an increase of pressure drop. The current results of friction factor and Colburn j factor are presented in terms of Reynolds number and staggered distance, and are expected to use for design and manufacture of such a system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.856-863
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• 1999

The thermal performance degradation of heat pipes is caused by the non-condensable gas generation mainly due to the electrochemical corrosion which results from the reaction of working fluids with tube materials. In this study, a simplified method described below was proposed to estimate the life of heat pipes concerning the non-condensable gas generation. The temperature distributions at the outer surface of heat pipes was measured, and based on them the amount of non-condensable gas of hydrogen was estimated. Applying it to the Arrhenius model, the mass generation of hydrogen and the volume occupied by the gas In heat pipes could be estimated for an operating temperature and time. Moreover, this simplified method was applied to the accelerated life test of nine methanol-stainless steel heat pipe samples.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2039-2042
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• 2008

Recently, Electronic & Electrical Products have problems how to reduce heat in trend reducing size and increasing speed. heat pipes worked by latent heats can solve problems for effective and quiet electronic applications. Heat Pipes have to be suitably designed for the external conditions due to showing optimum performance. it has influence on efficiency of heat pipes to the exterior structure changed by length, bending angle, diameter. Designing heat pipes has depended on experience from trial and error. this method wasted too many resources, but can't guarantee efficiency. to prevent those wastes, this study aims at making the thermal transfer coefficient predicting efficiency. In this study, the thermal transfer coefficient has been made from experimental results that used variables - lengths between heat source and radiation, bending angles, diameters of heat pipes. variables become non-dimensional in modeling process for making the coefficient.

• Journal of Korea Water Resources Association
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• v.32 no.4
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• pp.469-478
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• 1999

Explicit equations of minimum velocity, energy slope and pipe diameter are developed to ensure the cleaning of sewerage pipes. The equations of power form are employed for the estimation of critical shear stress of sediment particles and the friction factor of commercial pipes. They are all based on the existing laboratory data. Several cases are tested to check the values suggested in the manual, using the equations developed in the present study.