• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.286-291
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• 2008

Insulation of refrigerator with gasket material near door becomes the technical point at the aspect of heat loss and energy efficiency. Heat loss of refrigerator through the gasket is nearly 30%. In this paper, quantitative evaluation method of heat loss through gasket in established suggest the method for the improvement of heat loss. To analyze the heat transfer, we have used the common software Fluent that is used to CFD. Because of using the convection coefficient of heat transfer, we have solved only the equation of energy for heat transfer. As a result, we have known that heat loss flows through the heat flux vector and that the heat gathered out of the outside iron plate is transferred inner part through the gasket and ABS, etc. Through the result of the numerical simulation that use sub-gasket, we have known that we are able to reduce the heat loss about $20{\sim}40%$. when we applied that sub-gasket on a real refrigerator, the power consumption had reduced about 4.76%. In addition, when we applied a more improved sub-gasket on a real refrigerator and measured the power of the refrigerator the power consumption does reduce about 3% and we will try to apply the improved sub-gasket on a new models of refrigerator.

• Corrosion Science and Technology
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• 제19권4호
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• pp.196-202
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• 2020

The air vent connected to a heat supply pipeline in the district heating system has been used to eliminate the existing air in the pipe, which has a detrimental effect on corrosion durability and heat efficiency. Recently, the air vent installed under a manhole for 22 years was corroded and several pinholes were detected in the front-end of the air vent. To identify the cause of the failure, thickness reduction, corrosion products, and water quality were examined. The corrosion damage was significant at the outside of the front-end of the air vent where the insulator was covered. While a thin oxide layer was formed in the interior of the tube, the coarse and porous corrosion products consisting of magnetite and hematite were found externally. Water flowing into the thermal insulator was absorbed by the insulator following hydrolysis. The hydrolyzed insulator ejected the corrosion factors such as Cl^-, SO₄^2-, and NH₄⁺. The findings suggest that the corrosion under insulation due to rain water is the main cause of the underlying failure in the air vent.

• 설비공학논문집
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• 제28권12호
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• pp.483-488
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• 2016

In this study, we chose the rural house as a standard model. In order to review the energy difference of cooling and heating loads, we changed the thermal transmittance standards. By using the thermal transmittance standard in 2011 as the Basic CASE, the thermal transmittance standard in 2013 as well as 2016, and the thermal transmittance standard of passive houses, we compared the results with regard to the cooling and heating energy load. Because of the heat loss, it can be confirmed that with an improved thermal performance of the building structure, the maximum increase of the cooling energy load was 36 kWh from June to September. Because of the heat loss, it was also confirmed that with the improved thermal performance of a building structure, the maximum decrease of the heating energy load is 1,498 kWh from November to April. Even though the heat loss of the building structure could decrease the cooling energy load by improving thermal transmittance standards in Korea, the energy saving performance is worse than the situation of heating energy load in heating period. Compared with CASE 1 and CASE 2, as well as CASE 1 and CASE 3, we CASE 3 was found to have the best energy saving rate when compared to the other cases : CASE 3 increased by 1,452 kWh and CASE 2 by 588 kWh, because the window thermal transmittance standard of 2016 was added.

• 한국환경보건학회지
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• 제26권4호
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• pp.21-28
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• 2000

Various man-made mineral fibers(MMMF) including refractory ceramic fiber(RCF) have been used widely in industries as insulation materials. The effect of fibrous dust on human health depends on fiber size, concentration (exposure level), and durability in biological system. Therefore, these parameters should be determined to evaluate accurately the potential risk of fibers on human health. The purpose of this study was to characterize the size of airborne fiber and the workers＇ exposure to airborne fibers in refractory ceramic fiber manufacturing and processing factories. Airborne fibers were collected on 25-mm mixed cellulose ester membrane filters at personal breathing zones, and analyzed by A and B counting rules of the National Institute for Occupational Safety and Health(NIOSH) Method # 7400. The average ratios of the fiber density by B rule to the fiber density by A rule was 0.84. This result indicates that the proportion of respirable fibers (<3 ${\mu}{\textrm}{m}$ diameter) in air samples was high. The average diameter and length of airborne fibers were 1.05${\mu}{\textrm}{m}$ and 35${\mu}{\textrm}{m}$, respectively. The average fiber concentrations (GM) of all personal samples was 0.26f/cc, and the average concentration was highest at blanket cutting and packing processes. The fifty seven percent of personal air samples was exceeded the proposed American Conference of Governmental Industrial Hygienists(ACGIH) Threshold Limit Value(TLV), i.e. 0.2 f/cc. It was concluded that the RCF industrial workers had the higher potential health risk due to small fiber diameter, long fiber length, and high exposure level to the airborne fibers.

• 한국의류학회지
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• 제26권3_4호
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• pp.473-484
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• 2002

The physical characteristics of silk and wool fabrics dyed with OFS-FR and SM-FR were examined and color difference and colorfastness of these fabrics were analyzed. The results are as follows; 1. The thickness, density and weight of both dyed fabrics were increased than those of undyed fabrics independently of dyeing materials and mordants. 2. Air permeability of all the silk samples increased than that of undyed silk, on the other hand, air permeability of most of wool samples decreased than that of undyed wool. 3. Thermal insulation values of silk samples were not consistent with dyeing conditions, but those of wool samples increased than those of undyed fabrics regardless of dyeing materials and mordants. 4. Color difference was clear between OFS-FR and SM-FR dyed fabrics. The colors dyed with OFS-FR-Al and OFS-FR-chitos an showed violet, those dyed with SM-FR displayed yellowish, in addition to in case of wool, dyed with OFS-FR-Cu the color was greenish yellow, in case of silk dyed with SM-FR-Cu that was yellowish red. 5. Sense of silk fabrics by sensory-test was soft and smooth. Feeling of colors in silk fabrics was wick, warm and slightly brilliant. In case wool, sense of dyed fabrics was slightly soft and slightly rough. Feeling of colors in wool fabrics was warm but not elegant. Therefore the result of sensory-test in silk might be better than that of in wool. 6. Colorfastness to dry cleaning and perspirations was good, but that to washing and sunlight was not fine.

• 한국안전학회지
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• 제26권4호
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• pp.41-46
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• 2011

The purpose of this paper is to analyze the causes of accidents related to the 3 phase 170 kV gas insulated switchgear of a power system collected from accident sites to secure data for the prevention of similar accidents and provide important points of view regarding diagnosis for the prevention of accidents involving gas insulated switchgears. The analysis results of the causes of accidents involving gas insulated switchgears showed deformation of the manipulation lever installed at the S-phase, disconnection of the insulation rod connection, melting of the upper conductor, a damaged tulip, damage to the lower spacer and the spacer at the breaker, etc. It is believed from this result that the potential for accidents has expanded due to accumulated energy as a result of repeated deterioration. The carbonization depth of a GIS was formed near the screw (T2, T3) used to secure the lower pole of the S-phase tulip. It is not known what has caused the screws to be extruded and melted. However, it is thought that an unbalanced electromagnetic force, micro-discharge, surface discharge, etc., have occurred at that point. In addition, even though 16 years have passed since its installation, there was no installation defect, act of arson, accidental fire, etc. General periodical inspection and diagnosis failed to find the factors causing the accidents. As a system contained in a closed metal container, it has a high risk factor. Therefore, it is necessary to design, install and operate a GIS in accordance with the standard operational procedure (SOP). In addition, it is necessary to apply conversion technology for periodical SF6 gas analysis and precision safety diagnosis. It is expected that tracking and managing these changes in characteristics by recording the results on the history card will provide a significant accident prevention effect.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.1-8
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• 2012

오늘날 첨단산업의 발전과 지구환경 문제의 심각성에 대한 인식이 증가하여 시멘트 산업에서도 다각화 측면에서 다양한 종류의 기술들이 활성화되고 있는 시점이다. 본 연구에서는 최근에 새로이 검토되고 있는 시멘트 대체 재료로서 천연제올라이트를 주원료로 사용한 제올라이트 시멘트 콘크리트에 관한 기초 물성에 대해 분석하는데 목적이 있으며, 악취 및 유독가스 제거기능이 우수하며 중금속, 암모니아와 같은 양이온성 오염물질을 제거하는 이온교환능, 흡착능, 분자체효과를 가지며 또한 다공성 물질이라 보온능력이 좋은 것으로 알려진 천연제올라이트와 알칼리 활성제(NaOH)의 양에 따라 콘크리트의 압축강도, 슬럼프, 블리딩 및 공기량 등을 실험하였다. 천연제올라이트 콘크리트의 압축강도 측정결과 거의 40MPa정도로 측정되었으며 슬럼프, 블리딩, 공기량 시험에서도 일반 콘크리트과 비슷한 성능을 나타내어 향후 고성능, 고기능성 건설재료로 사용 가능하다고 판단되어진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1988-1989
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• 2007

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. We have already reported that the dissipation currents of $40\;{\mu}m$ thick LDPE film at 10 kV/mm and over 140 Hz, it starts to show nonlinearity and odd number's harmonics were getting large. To investigate the conduction mechanis ms in this region, especially space charge effect, various kinds of estimation, such as time variations of instantaneous resistivity for one cycle, FFT spectra of dissipation current waveforms and so on, has been examined. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.710-721
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• 2020

본 연구에서는 시멘트, 벽돌, 목재를 이용한 건축모형을 이용하여 직경 900 mm의 밀폐된 환경 속에서 3일간 온도와 상대습도 측정을 통하여 건축소재의 종류에 따른 실내 온도 환경에 미치는 영향과 열 이동 특성에 대해서 비교분석하였다. 건축모형 내부에 설치된 물은 실내에 있는 사람을 나타냈으며 사람에게 어떤 영향을 미치는지 평가하고자 사용되었다. 목조 건축모형은 시멘트, 벽돌 건축물 보다 보온성이 높아 열 손실이 가장 낮은 것으로 나타났다. 각각의 건축 모형의 열적 쾌적성은 온도와 상대습도를 이용하여 산출하였으며 목조 건축 모형은 시멘트, 벽돌 건축 모형보다 더 쾌적한 환경을 조성하는 결과를 도출하였다.

• 한국재료학회지
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• 제22권10호
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• pp.531-538
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• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.