• 한국분무공학회지
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• 제15권2호
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• pp.94-99
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• 2010

The object of this investigation is to study the thermal properties and spray characteristics of kerosene fuel in high temperature and pressure conditions. In order to investigate the thermal properties and spray characteristics, KIVA3 and SUPERTRAPP have been used at the same time. The thermal properties of kerosene has been calculated in high temperature and pressure condition using SUPERTRAPP. The study of spray characteristics has been conducted at both original properties of KIVA3 and calculated properties. The evaporation rate was increased in proportion to pressure when the calculated properties were used. However, the effect of pressure was not shown in the case of using original properties. So the calculated properties are more effective than original properties in high temperature and high pressure condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1912-1914
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• 2005

The electrical, chemical and mechanical characteristics in transformer insulations are changed due to thermal stress. It is known that characteristics of transformer insulations is deteriorated such as decrease of dielectric strength, deterioration of dielectric constant and tensile strength of paper as transformer oil and paper are aged by thermal stress. Furthermore, chemical characteristics of them are deteriorated as like increment of moisture contents and dissolved by-products in oil, etc. In this paper we have been investigated chemical characteristics of transformer by accelerated thermal aging. For this working we have made experimental test cell and aged at a temperature up to $140^{\circ}C$ for 500 hours. The oil-paper insulation samples have been measured at intervals of 100 hours. For analysis we used Karl-Fisher titration method and high performance liquid chromatography (HPLC).

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.114-114
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• 2001

The thermal and friction characteristics of phenolic resin and model friction materials were investigated with the content of acrylonitrilebutadienerubber(NBR). The thermal characteristics of material was performed by dynamic mechanical thermal analysis and differential scanning calorimetry. The friction and wear characteristics of the material were determined by using friction material testing machine. The results show that with the more content of rubber, the loss modulus of friction material was increased. The friction coefficient and the specific wear rate with various NBR contents were reported.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1312-1314
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• 1998

SOFC system is often subject to thermal cycle condition during normal start/stop, shutdown, and emergence state. Under the thermal cycle condition of heating and cooling, the SOFC components expand or shrink, which produces thermal stress and thermal shock. The SOFC performance is degraded by the thermal factors. To protect SOFC system from the thermal degradation, the optimum thermal condition must be clarified. In this study, to examine the thermal cycle characteristics, we fabricated single cells of planar SOFC with an area of $5{\times}5cm$. The electrolyte and PEN were tested under thermal cycle conditions in the range of$ 2-8^{\circ}C/min$. After thermal cycle test. crack creation of the components were examined using ultraviolet apparatus. No crack in the electrolyte and PEN were observed. The single cell system with alumina frame were also tested under thermal cycle conditions of 2, 3, $4^{\circ}C/min$. The single cell was fractured at the thermal cycle of 3 and $4^{\circ}C/min$ and the optimum condition of the thermal cycle to be found below $2^{\circ}C/min$.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2789-2802
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• 2020

Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권12호
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• pp.725-731
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• 2004

In this study, the three type hybrid interrupters according to the arrangement of the thermal expansion chamber and the puffer cylinder(they are called 'serial type', 'parallel/exchanged type', and 'parallel/separated type' respectively in this work) were designed and manufactured. This paper presents the tested results of the thermal recovery characteristics on the interrupters using a simplified synthetic test facility. The 'serial type' hybrid interrupter which is to obtain more easily the pressure rise for the thermal recovery compared with the others has the best capability in the thermal recovery characteristics. In order to investigate the stress on the operating mechanism, the distortion of the stroke wave in on-load test was examined to the stroke curve in no-load test. The biggest distortion was occurred in the 'parallel/exchanged type' hybrid interrupter. Finally, the small interruption capability on the three type interrupters was estimated by a theoretical form and the 'parallel/separated type' hybrid interrupter has the advantage of the others in the view of structure.

• Safety and Health at Work
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• 제11권4호
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• pp.405-417
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• 2020

Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets' conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 ℃. In relation to the installation year (30 years), insulation resistance decreased from 70 ℃, which is as much as 40 ℃ lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 ℃ of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 ℃. It is necessary to manage electrical socket outlets that have been installed for a long time.

• 기술사
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• 제32권6호
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• pp.60-67
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• 1999

299 chemical analyses are used to study the characteristics of mineral and thermal waters in South Korea. Even though the concentration of chemical components in thermal waters are generally very low, mineral waters having components more than 1,000 ppm of dissolved total solid(TDS) are reached up to 19% total analyses data, In Germany, Japan or some other countries, mineral and thermal waters are detined not only by water temperature, but also by chemical components. The principle of Law in Japan in also almost same with the German regulations. However, the Law for thermal spring In Korea permit thermal water to be qualifiled only by water temperature. For including chemical characters into the regulations or Law of thermal spring, the limit values of TDS and other 9 micro components related to mineral and thermal waters was selected through this study.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.1023-1027
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• 2000

In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models of the thermal errors for error analysis and develops on-the-machine measurement system by which the volumetric error are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses, a designed spherical ball artifact, and five gap sensors. In order to analyze the thermal characteristics under several operating conditions, experiments performed with the touch probe unit and five gap sensors on the vertical and horizontal machining centers.

• 기술사
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• 제33권1호
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• pp.75-82
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• 2000

299 chemical analyses are used to study the characteristics of mineral and thermal waters in South Korea. Even though the concentration of chemical components in thermal waters are generally very low, mineral waters having components more than 1,000 ppm of dissolved total solid(TDS) are reached up to 1975 of total analyses data, In Germany, Japan or some other countries, mineral and thermal waters are defined not only by water temperature, but also by chemical components. The principle of Law in Japan is also almost same with the German regulations. However, the Law for thermal spring In Korea permit thermal water to be qualifiled only by water temperature. For including chemical characters into the regulations or Law of thermal spring, the limit values of TDS and other 9 micro components related to mineral and thermal waters was selected through this study.