• Proceedings of the KSME Conference
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• 2001.06d
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• pp.365-370
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• 2001

There are various wick types for heat pipe. In the present study, the manufacturing technology of a sintered wick among various wick types is discussed. The sintering technology using metal has been applied broadly in the field of electronic-telecommunication as well as heat pipes. A study of manufacturing procedure and characteristic of sintered wick for heat pipe have been performed. Copper powder was used as wick material and stainless steel as a mandrel. A manufacturing technology of the mandrel for arranging vapor core in heat pipe, a sintering technology by first or second times and operating temperature for sintering, the measurements of a porosity, pore size, and pore distribution of sintered wick were considered. In the meantime, a heat pipe with sintered wick has been manufactured and a performance test of the heat pipe has been performed in order to review cooling performance. The performance test results for the 4mm diameter heat pipe with the sintered wick shows the stability since the temperature difference between a evaporator and a condenser of the heat pipe is less than $4.4^{\circ}C$, and thermal resistance is less than $0.7^{\circ}C/W$.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.107-113
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• 2015

The goal of this paper is to investigate structural integrity factors of RMI(reflective metal insulation) to confirm the design requirements in nuclear power plant. Currently, a glass wool insulation is using now, but it will gradually be replaced with the reflective metal insulation maded by stainless steel plates. The main function of an insulation is to minimize a heat loss of vessel and pipes in RCS(reactor coolant system). It has to maintain structural a integrity in nuclear power plant life duration. In this study, the structural integrity analysis was carried out both multi-plate and outer shell plate by using a static analysis and experimental test. First, inner multi-plate has a self support structure for being air space. Because the effect of total static weight in multi-layer plate is low, a plate collapse possibility is not high. Considering optimum thin plate pressing process, it has to pre-check the basic physical properties. Second, the outer segment thickness and stiffener shape are verified by the numerical static analysis, and sample test for both type of panel and cylindrical pipe model.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1216-1224
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• 2000

The collapse pressure of tubes is determined experimentally by Tschoepe and Maison for various materials with different geometries. The results are compared with those obtained by ASME Codes UG-31 and UG-28. A collage pressure is the pressure required for the incipient yielding stress of the tubes with and without ovality. This collapse pressure is compared with the experimental results by Tschoepe and Maison. The present investigation is towards finding the collapse pressure required to bring the entire wall of tubes into a state of plastic flow for the pipes, with ovality and without ovality. This collapse pressure is compared with the collapse pressure obtained through experiments in the present investigation. The experimental results are compared with the pressure obtained by FEM(finite element methods). The FEM results are then compared with results obtained through an approximate plastic analysis of the strain hardening material, SA312-TP304 stainless steel. The structural integrity evaluation is performed for the heat exchanger used in an actual nuclear power plant by using various methods described in this paper. The results obtained by the various analyses and the FEM are discussed. consequently, the paper is oriented towards an actual design purpose of d heat exchanger in an industrial environment, rather than for the purpose of an academic research project investigation.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1672-1677
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• 2003

Carbon dioxide($CO_2$, R-744) has become a very popular issue in application to refrigeration and air conditioning systems as a natural refrigerant. An experimental study has been carried out to investigate the vapor pressure and miscibility of refrigerant R-744 in the presence of lubricant oil. This is of particular interest in the selection of the lubricant oil for the compressor of a refrigeration system or an air conditioning system using the refrigerant R-744. This apparatus consists of the test section, measuring devices, the vacuum pump, the constant temperature bath and relevant connecting pipes made of stainless steel. Two lubricant oils, such as mineral oil(Naphthenic) and polyol ester(POE) oil, are considered in the present study. For this purpose, test runs were conducted with the oil concentration range from 5 to 50 wt%, and the temperature range from -10 to $10^{\circ}C$ with $2^{\circ}C$ intervals. The results are correlated with the vapor pressure. and showed with the miscibility as visualization for the individual text components.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.73-77
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• 2002

In order to derive the detailed design of Thermal Shield Cryopanel. which plays a role to make the Tokamak Nuclear Fusion Equipment work at both static and efficient conditions the commercially available software package FLUENT Version 5.3, was utilized. This study investigated the effects of thermal sources and distributions on the temperatures of Lid. Body. Base. and EH-Port Cryopanel by the numerical technique whose grid generations cover the solid and 9as region of the panel. The physical model of the Thermal Shield Cryopanel is that the 10mm diameter of the pipe with 1mm thickness is soldered on the Stainless steel Panel with 4mm thickness. The heat fluxes to the panel are assumed to be by thermal radiation in the vacuum space and by conduction through the supporters. The inlet conditions of Helium gas are 20 atmospheric Pressures and 60K temperature. The panel shapes with cooling Pipes and the operational conditions to keep appropriate temperature distribution of Thermal Shield Cryopanel Have been found and suggested.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.68-73
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• 2011

An experimental study was conducted to investigate the thermal performance of a medium-temperature heat pipe against the charge amount of working fluid. The container and the wick of the heat pipe were made of stainless steel and the working fluid was Dowtherm-A for medium-temperature applications around $250^{\circ}C$. The diameter and length of the heat pipe were 25.4 mm and 1 m, respectively. The maximum thermal load was 1 kW and the working fluid charge ratio varied from 372% to 420%. The results showed that the thermal resistance ranged from 0.12 to $250^{\circ}C/W$ and the effective thermal conductance ranged from 7,703 to $8,898 W/m{\cdot}K$. Dry-out occurred for the heat pipe with 372% fill-charge at the heat load of 950 W, while the other heat pipes with higher charge amount did not encounter dry-out up to 1060 W.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.2
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• pp.150-157
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• 2004

Carbon dioxide ($CO_2$, R-744) has become a very popular issue in application to refrigeration and air conditioning systems as a natural refrigerant. An experimental study has been carried out to investigate miscibility and the vapor pressure of refrigerant R-744 in the presence of lubricant oil. This is of particular interest in the selection of the lubricant oil for the compressor of a refrigeration system or an air conditioning system using the refrigerant R-744. The experimental set-up consists of the equilibrium cell, measuring devices, the vacuum pump, the constant temperature bath and relevant connecting pipes made of stainless steel. Five lubricant oils, such as mineral oil (Naphthenic), AB (Alkyl Benzene) oil, PAO (Poly Alpha Olefin) oil, PAG (Poly Alkylene Glycol) oil and POE (Polyol Ester) oil are considered in the present study. Test runs were conducted with the oil concentration range from 5 to 50 wt％, and the temperature range from -10 to 1$0^{\circ}C$ with 2$^{\circ}C$ intervals. The miscibility results are visualized and correlated with the vapor pressure for the individual test components.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.130-139
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• 2023

This paper examines the quantification of uncertainty for welding residual stresses in dissimilar metal welds used in nuclear power plants. A mock-up of a dissimilar metal weld pipe, consisting of carbon and stainless steel pipes, was fabricated to measure the residual stress. A Round-Robin analysis was conducted by Korean institutions to assess the welding residual stress. The analysis was carried out in the second order, and the data obtained by each institution was evaluated based on the information provided. Using the Round-Robin results, the distribution of uncertainty in welding residual stresses among Korean institutions was evaluated. The quantification of uncertainty for Korean institutions was found to have a wider range compared to the distribution of welding residual stresses observed in overseas institutions. This study is considered useful in the establishment of comprehensive strategies for evaluating welding residual stress analysis methods used by domestic institutions.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.52-60
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• 2015

Nuclear power plant contain many dissimilar metal welds that connect carbon steel components with stainless steel pipes using alloy600 welding materials. Primary water stress corrosion cracks at dissimilar metal welds have been continuously reported around the world. In periodic integrity evaluations, dissimilar metal welds are examined using a generic ultrasonic testing procedure, KPD-UT-10. In this procedure, the gap between the probe and examination surface is limited to 1/32 inch (0.8mm). It is not easy to test some dissimilar metal welds in Korean plants applying ordinary technology because of their tapered shapes and irregular surface conditions. This paper introduces a method for applying a flexible phased array technology to improve the reliability of ultrasonic testing results for various shapes and surface conditions. The artificial flaws in specimens with irregular surfaces were completely detected using the flexible phased array ultrasonic technology. Therefore, it can be said that the technology is applicable to field examination.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.73-82
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• 2017

In Korea, previous certification of water supply infrastructure was mainly focused on economical and physical aspects. Recently, hygienic safety of water supply service has become a sensitive and important issue to our people for evaluating the water quality with growth of economy and education system. According on water quality in 497 Korean water supply facilities, pH values in the supplied water have ranged between 5.8-8.5. However, little is known about metal leachability at the pH conditions observed in the real water supply systems because a fixed pH condition (pH 7.0) has been used in the current standard method, 'Hygienic Safety Testing Method', in water supply. In this work, we examined the effects on heavy metal leachability with pH differences in the water supply pipes which are typically used in Korea. As a result, the amounts of metal leachability were tended to increase when pH levels were decreased. Especially at pH 5.8, Cu leachability from Cu pipes was found to exceed the public health standard level even after applying a normalization factor (NF) given by the current Korea standard method. The Cr and Cu leached from stainless steel pipes, Cd, Pb, Cu, and Zn from Cu-based pipe fittings, and Zn from Zn-based pipe fittings were exceeded the Korean hygienic safety standards while, after applying the NF, concentrations of the leached metals were satisfied with the current Korean standard. The findings from this work provide implications on the needs of reforming the current hygienic safety standard methodology.