• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.727-734
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• 2015

Currently, polyurethane (PU) foam is used in most refrigerators as a thermal insulator, whereby the material contributes to structural stiffness by joining the refrigerator cases; however, refrigerator PU foam induces a low thermal efficiency and results in environmental contamination. To resolve these issues, we applied the vacuum insulated panel (VIP) instead of PU form in the design of a new refrigerator type, whereby the VIP significantly contributes to the rectification of the previously mentioned issues. The VIP structure, however, cannot effectively hold refrigerator cases, so the present study investigated a new frame-structure concept by evaluating the stiffness using the topology optimization of refrigerator cases. Lastly, a refrigerator prototype comprising an optimal frame structure was built and subject to a stiffness test, and a comparison of the test results with those of a conventional refrigerator show that the structural stiffness of the prototype is sufficiently effective.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.89-94
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• 2019

Glass base sealant is required as a ceramic-ceramic joining material between α-alumina insulation cap and β-alumina electrolyte tube in the development of NaS battery cell package for electrical energy storage system. The fabrication of glass frit by thermal quenching method, phase analysis, particle size analysis, coefficient of thermal expansion and surface roughness according to the glass compositions were analyzed for the fabrication of glass sealing paste for ceramic-ceramic joining. Also, a new evaluation method of the adhesion strength of glass sealant at the small area in ceramic-ceramic joining component was proposed using conventional Dage bond tester that was used to measure the adhesion of solder ball joint.

• Smart Structures and Systems
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• v.30 no.3
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• pp.327-332
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• 2022

In building envelope, transparent components play an important role. The structural glazing systems are the weak element of the casing in terms of mechanical resistance, thermal and acoustic insulation. In the present work, new structural glass panels with granular aerogel in interspace were investigated from different points of view. In particular, the mechanical characterization was carried out in order to assess the resistance to bending of the single glazing pane. To this end, a special instrument system was built to define an alternative configuration of the coaxial double ring test, able to predict the fracture strength of glass large samples (400 × 400 mm) without overpressure. The thermal and lighting performance of an innovative double-glazing façade with granular aerogel was evaluated. An experimental campaign at pilot scale was developed: it is composed of two boxes of about 1.60 × 2 m² and 2 m high together with an external weather station. The rooms, identical in terms of size, construction materials, and orientation, are equipped with a two-wing window in the south wall surface: the first one has a standard glazing solution (double glazing with air in interspace), the second room is equipped with the innovative double-glazing system with aerogel. The indoor mean air temperature and the surface temperature of the glass panes were monitored together with the illuminance data for the lighting characterization. Finally, a brief energy characterization of the performance of the material was carried out by means of dynamic simulation models when the proposed solution is applied to real case studies.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.447-454
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• 2020

Since SF₆ gas was discovered in the early 1900s, it has been widely used as an insulation material for electrical equipment. While various indicators have been developed to diagnose oil-immersed transformers, there are still insufficient indicators for the diagnosis of gas-insulated transformers. When necessary, chemical diagnostic methods can be used for gas-insulated transformers. However, the field suitability and accuracy of those methods for transformer diagnosis have not been verified. In addition, since various types of decomposition gases are generated therein, it is also necessary to establish appropriate analysis methods to cover the variety of gases. In this study, a gas-insulated transformer was diagnosed through the analysis of decomposition gases. Reliability assessments of both simple analysis methods suitable for on-site tests and precise analysis methods for laboratory level tests were performed. Using these methods, a gas analysis was performed for the internal decomposition gases of a 154 kV transformer in operation. In addition, simulated discharge and thermal fault experiments were demonstrated. Each major decomposition gas generation characteristics was identified. The results showed that an approximate diagnosis of the inside of a gas-insulated transformer is possible by analyzing SO₂, SOF₂, and CO using simple analysis methods on-site. In addition, since there are differences in the types of decomposition gas generation patterns with various solid materials of the internal transformer, a detailed examination should be performed by using precise analysis methods in the laboratory.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.225-232
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• 2023

In this study, poly(ethylene-co-vinyl acetate)/magnesium hydroxide (EVA/MDH) composites were prepared by electron beam crosslinking. EVA as a matrix resin and MDH as a flame retardant were melt-blended and compression molded to prepare EVA/MDH composites. The prepared EVA/MDH composites were electron beam-irradiated at various absorbed doses of 50~200kGy. The effects of electron beam irradiation on the gel content, tensile strength, elongation-at-break, thermal properties, and flame retardancy of the composites were investigated. The gel content and tensile strength increased, while the elongation-at-break decreased with an increase in the absorbed dose due to the formation of crosslinked network structures. In addition, the thermal stability and flame retardancy improved as the absorbed dose increased. Therefore, the EVA/MDH composites prepared in this study can be used as an insulation material for flame-retardant and heat-resistant wires and cables.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.27-33
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• 2023

An optimized design of the transportation insulated box must be considered to control the thermal damage in order to maintain the fresh condition for temperature-sensitive medicine and frozen food safety. The inside temperature of the insulated box is a natural convection enclosure state, thermal stratification naturally occurs as time passes in case of with outside heat load. The latent heat material (LHM) placement inside the box maintains the target temperature of the product for temperature fluctuations during transport, and LHM application is a common and efficient method. In this work, inside temperature stratification in an insulated box depending on the LHM pack position is numerically simulated and experimented. The insulated box is made up of vacuum insulation panel (VIP), and LHM modules are placed over six faces inside the box, with the same weight. The temperature curves for 72 hrs as experiment results clearly show the temperature stratification in the upper, middle, and lower at the LHM melting time region. However, the temperature stratification state is uniformly changed in accordance with the condition of the upper and lower placement weight of the LHM pack. And also, the temperature uniformity by changed placement weight of LHM has an effect on maintaining time for target air temperature inside the box. These results provide information on the optimized design of the insulated box with LHM.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.4
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• pp.201-208
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• 2011

Objectives: According to the compliance of the asbestos-related regulation, every building has to be inspected for asbestos presence before its abatement work. This study was performed for identifying the types and contents of asbestos in building bulk samples. Materials and Methods: Bulk samples were collected during the asbestos inspection in 2010. We grouped the bulk samples into the regulated asbestos containing materials(RACM), presumed asbestos containing materials(PACM), and construction products. Additionally, the types of asbestos in all bulk samples were identified by polarization microscopy(PLM). Results: The RACMs were from building, house, pipe and facility. The RACMs were found mainly building (72.1%) and house (93.7%). The contents of chrysotile in building, house and facility were 66.9% (1-90%), 89.7% (2-90%) and 11.0% (2-90%), respectively. PACMs were surfacing material, thermal system insulation (TSI), and miscellaneous material. The miscellaneous materials that showed a high detection rate (79.2%) were ceiling, roofing and wall materials. Among them, the roofing materials had high chrysotile content(9.7%, 2-21%), followed by wall (8.7%, 2-21%) and ceiling (3.4%, 1-17%). In the construction products, asbestos was found mainly in slate (92.6%, 2-21%), including chrysotile. The slate had high asbestos content (9.7%, 2-21%), followed by cement flat board (8.7%, 2-19%) and textile (3.4%, 1-17%) Conclusions: Utilizing these results, it would be contributed to construct a useful ACM database and prevent from asbestos exposure to workers in the asbestos abatement and maintenance works.

• Fashion & Textile Research Journal
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• v.15 no.2
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• pp.231-239
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• 2013

This research developed a smart girdle for adult women in their 20's that has an inserted carbon weaving heater to help with relief from coldness and abdominal disease through the thermal insulation effect. A pocket of powernet fabric was attached to the inside of the girdle for the easy insertion and separation of the heating device, while the heating device was fixed to a mesh material by cotton yarn and was wrapped with elastic lining material to prevent the mechanical devices from being exposed. A set of 3 hooks was attached to the center of the back of the heating device in consideration of convenience and mobility. Whereas the switch was inserted into around the right waistband, and the battery into the inner pocket around the waist, to integrate the heating device with the girdle. The satisfaction and usability of the fabricated smart girdle was verified by having research participants wear it to evaluate the appearance change caused by the device, the inconvenience of wearing/unwearing, mobility, and the satisfactory functionality of the device. As a result, the grand mean was evaluated to be high, with appearance (4.19), mobility (4.17), and functionality (4.51) being higher than 4.00; which indicates that the heat generation function of the smart girdle is effective. It may be said that such collection and analysis of data that reflect users' opinions have value and significance in that they can be grafted onto future research on new technology as well as they contribute to taking a step forward in the rapidly increasing research of smart clothing, with the new-type clothing equipped with new function.

• Fire Science and Engineering
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• v.20 no.4 s.64
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• pp.33-41
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• 2006

Nowadays in Korea, KS F 2271(Testing method for incombustibility of internal finish material and element of buildings) has been using for the evaluation of fire safety performance of sandwich panels. The test method in Japan and in Korea was based on the same way. When the Japanese standard building code was revised in 2000, the test method in the ISO 5660-1 was adopted for the test method for combustion performance of internal finishing materials and elements of buildings. According to this, the revision version of draft substituting the test method in the KS F 2271 for one in the ISO 5660-1(Cone Calorimeter method) is informed in Korea. In this study, combustion properties of sandwich panels were tested using the cone calorimeter method. Ignition time, peak heat release rate and total heat released of four sandwich panels and four core materials (thermal insulation material), which are widely used in Korea, were tested. Test results were analyzed for each specimen. Finally, test results were classified by Japanese standard building code and Canadian NBC revised.