• Nuclear Engineering and Technology
• /
• v.56 no.10
• /
• pp.4184-4194
• /
• 2024

New technologies in polymer synthesis and pipe extrusion equipment have led to the commercialization of high-performance, large-diameter, thick-wall high density polyethylene (HDPE) pipes. They have been used in the field of seawater transport and cooling to replace metal pipes, due to their advantages of high corrosion resistance and extensibility. Connection of HDPE pipe is important as it determines the safety of the entire piping system. Butt fusion welding is commonly used for HDPE pipe connection but may cause the formation of weak points in the welded joints, interfering the reliability of the pipeline system in the application of nuclear power plants. At present, there is a lack of research on evaluating the performance of welded joint for large-diameter thick-wall HDPE pipes made by butt fusion-welding. The purpose of this study is to investigate the influence of three different butt fusion-welding processes, i.e., single low pressure (SLP), single high pressure (SHP) and dual low pressure (DLP), by evaluating the performance of their welded joints, including characterizing tensile strength, extensibility, crystallinity and hardness. In specific, a thick-wall HDPE pipe with OD of 812.8 mm and wall thickness of 74 mm which is certified for nuclear safety class was used for study. Representative specimen from the outer, middle and inner part across the wall of the main pipe body and welded joints were taken for testing. Different test methods and specimens were designed to assess the feasibility of evaluating the welding performance from different welding process. The results showed that the mechanical properties of different locations of the welded joints were different, and the tensile strength and fracture energy of the middle part of the joint were lower than that of the inner and outer parts, which could be caused by the difference in the crystallinity and thickness of the melting zone influenced by welding processes, as can be seen from the analysis of DSC test and morphology observation. Hardness testing was conducted on the section of the welded joints, and it revealed that the micromechanical properties of the welded joints in the region of the heat-affected zone were enhanced significantly, which may be due to the annealing effect caused by welding process. In summary, The DLP process resulted in the best extensibility of the welded joints among three processes, suggesting that the joining pressure from welding process plays an important role in affecting the extensibility of the welded joints.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.11 no.2
• /
• pp.12-18
• /
• 2015

The energy pile, used for both structural foundations and heat exchangers, brings about heat exchange with the ground formation by circulating a working fluid for heating and cooling buildings. As heat exchange occurs in the energy pile, thermal stress and strain is generated in the pile body and surrounding ground formation. In order to investigate the thermo-mechanical behavior of an energy pile, a comprehensive experimental program was conducted, monitoring the thermal stress of a cast-in place energy pile equipped with five pairs of U-type heat exchanger pipes. The heating and cooling simulation both continued for 30 days. The thermal strain in the longitudinal direction of the energy pile was monitored for a 15 operation days and another 15 days monitoring followed, without the application of heat exchange. In addition, a finite element model was developed to simulate the thermo-mechanical behavior of the energy pile. A non-linear contact model was adopted to interpret the interaction at the pile-soil interface, and thermal-induced structure mechanics was considered to handle the thermo-mechanical coupled multi-field problem.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.815-822
• /
• 1999

This program is developed to design Prestressed Concrete Cylinder Pipes (PCCP), Fittings and Thurst Blocks and to manage drawings, quantity calculations and calculation data, using Graphic User Interface(GUI), which is capble of not only reducing the time taken to design, but also enabling the user to achieve such a design even when operator has no theoretical knowledge of that design while only having knowledge of data inputting and outputting. PCCP is used in water transmission popeline of the Great Man-made River Project. In domestic area, PCCP is used for water cooling systems of Uljin and Youngkwang nuclear power. In abroad, especially in the United States and Canada PCCP applies virtually every metropolitan area with raw and treated water.

• Journal of Advanced Marine Engineering and Technology
• /
• v.15 no.5
• /
• pp.38-46
• /
• 1991

In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air-conditioning systems are being operated during daytime in summer season. Therefore, it is necessary to construct an additional electric power plant and to develop the new air-conditioning system for relieving the peak load. This paper analysed the performance characteristics of this experimental regenerative ice energy system by means of a bundle of the heat-pipes. And the result of this analysis was applied to the simulation of an air-conditioning system model. Also, an operation program of moisture air was made according to air load and in order to computerize the air-conditioning system a CAD program was developed by the properties of moisture air.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1623-1628
• /
• 2004

Recently mini-channels or micro-channels are widely used for cooling the high density power electronic devices. Especially, the channels are used in small and high efficient equipments such as heat pipes and heat exchangers. Interfacial velocities between liquid and gas phases are very important in mini or micro-channels. In this paper, an experiment and a numerical analysis on the interfacial velocities were performed. In the experiment, the interfacial velocities which were measured by the high-speed CCD camera were about $26{\sim}33$ cm/s and the velocities increased as the inclination angle did. In the numerical experiment, CFD-ACE+, a commercial program, was used, the velocities had similar values with experimental results. As the inclination angle and the contact angle increased, the interfacial velocities did because of the surface tension which causes to move the interface. The effect of inclination angle was larger in the converging channels than in straight channels.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.6
• /
• pp.701-706
• /
• 2005

Pipes, tubes. and tubular sections with external transverse high fins have been used extensively for heating cooling, and degumidifying air and other gases. This work was performed to investigate an air side heat transfer charactieristics of minichannel with tension wound transverse fin. This estimate was confirmed conversion heat capacity the air side surface area enlargement and heat transfer charactieristics performed available inlet tube side hot water mass flux or outlet tube side air frontal air velocity. The most suitable tension wound transverse finned minichannel was measured extremely low in air side pressure drop and fin effectiveness $3.3\~4.4$. The pressure drop $0.9\~2.8Pa$ was ranged frontal air velocity $0.5\~1.2m/s$. It is also appeared that heat transfer in air side could be better conversion heat area which has been increased $330\%$ of heat capacity compared with the bare tube.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.361-366
• /
• 2001

The purpose of installation of the brine heating system for LNG storage tank is the prevention of ground freezing. If the ground of LNG tank areas is frozen, it is caused by safety problems. The design of brine heating system for LNG storage tank which is constructing in our country is not well considered about domestic weather conditions and economical efficiency. Therefore, this paper reports on the study of the optimized temperature of inside pipes and cooling process through the transient analysis by using the existing brine heating system.

• Journal of Welding and Joining
• /
• v.21 no.6
• /
• pp.64-70
• /
• 2003

Multipass welds of the 316L stainless steel have been widely employed in the pipes of Liquid Metal Reactor. Owing to localized heating and subsequent rapid cooling by the welding process, the residual stress arises in the weld of the pipe. In this study, the residual stresses in the 316L stainless steel pipe welds were calculated by the finite element method using ANSYS code. Also, the residual stresses both on the surface and in the interior of the thickness were measured by HRPD(High Resolution Powder Diffractometer) instrumented in HANARO Reactor. The experimental data and the calculated results were compared and the characteristics of the distribution of the residual stress discussed.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.735-741
• /
• 2005

We have studied the prearranged plan and the economy of a candidate site for the development of small hydro power. And also we have confirmed its economy by suggesting the technology of the unmanned operation and the selection of the water turbine generator which has a great efficiency, working rate and suitability to the topographical characteristics of various development sites, for example, irrigation reservoirs, water works pipes, sewage systems and cooling water of a steam power station. We proposed some opinions such as the better improvement of small hydropower industry the people' view, cooperation among industry/university/ research institutes, remote control/maintenance and goverment's legislature and supporting system etc.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.309-314
• /
• 2008

increased heat dissipation and higher heat density of electronic equipment and/or parts released. A loop heat pipe(LHP) has been payed closer attention to the potential candidate of an electronic cooling. As of the LHP with a circular plate type evaporator developed, this study focused on its operating characteristics on the steady state in accordance with charging different working fluid. The relationship between working fluid and operating characteristics is discussed.