• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.798-803
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• 2007

The brake system of railway plays an important role to enhance the speed of train, and the brake disc is one of major components relating to frictional braking. The performance enhancement of brake disc directly affects the braking performance of train. It is required to understand and investigate the factors need to be considered for the development of new brake disc with improved materials and performance. In this study, through the literature reviews of previous study, several factors including thermal crack phenomena, friction coefficient, materials and durability of disc, temperature characteristics, etc., were introduced for the design of improved brake disc. Moreover, based on the review results, the design direction of new brake disc was suggested. Eventually, a new brake disc with improved performance would be developed based on this investigation.

• 한국항공우주학회지
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• 제43권12호
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• pp.1079-1088
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• 2015

본 연구는 한국항공우주연구원에서 개발한 위성종합설계 SW 내의 복사계수 계산 프로그램의 병렬화 및 성능향상에 대해 논의한다. 복사계수는 복사열전달이 포함된 인공위성의 열해석을 수행하기 위한 필수적인 전초 단계로서 그 자체적인 계산량 또한 상당하다. 특히 위성 궤도상 시간에 따라 태양전지판과 본체의 상대변위가 변하기에 시간 별 독립적인 복사계수의 계산이 필요하다. 본 논문은 복사형상계수 병렬화 방법과 그 성능, KD-Tree 기반 차폐 탐색 알고리즘 및 태양전지판과 본체의 상대변위 변화에 따른 부분 복사형상계수 행렬 갱신이라고 지칭하는 계산량 저감 기법에 대해 논한다.

• 한국화재소방학회논문지
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• 제16권1호
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• pp.66-76
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• 2002

본 연구는 지하구 미분무수 소화설비 적용에 관한 것으로, 화재 초기에 신속한 소화를 통한 케이블 열적손상의 최소화와 신속한 본래 기능의 회복을 위한 소화 시스템의 최적화에 그 목적이 있으며, 이를 위해 미분무수 노즐개발을 위한 화재실험을 수행하였다. 실험은 2.5m(H)$\times$2.5m(W)$\times$25m(D)의 콘크리트 지하구에서 소화설비가 작동되지 않는 경우와 2가지 종류의 미분무수노즐이 적용되는 경우를 수행하였다. 실험 결과 소화설비의 개입이 없는 경우, 2분 이내에 열적 변형에 의한 치명적인 손상을 입었으며, 2～3분 경과 후 케이블의 내부까지 손상되었다. 노즐적용실험의 결과, 타입 1(입자분포 약 470$\mu{m}$)노즐과 타입 2(입자분포 약 650$\mu{m}$) 노즐은 모두 케이블의 피해 온도제어($4000^{\circ}c$ 이하)를 만족하였다. 실험을 통하여 지하구 공간특성에 적합한 미분무수 헤드의 특성을 설정할 수 있었으며, 그 성능을 입증할 수 있었다.

• 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.

• 산업기술연구
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• 제25권B호
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• pp.73-80
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• 2005

Durability of concrete structures is seriously compromised by cracking at early-age concretes, particularly in high-strength or high-performance concrete structures. Since early-age cracking is influenced by various factors that affect the hydration process, early-age shrinkage and stress/strain development, the behavior at early-age is highly complex and no rational methodologies for its control have yet been established. Concrete structures often present volumetrical changes particularly due to thermal and moisture related shrinkages. Volumetric instability is detrimental to the performance and durability of concrete structures because structural elements are usually restrained. These restrained shrinkages develope tensile stresses which often results in cracking in combination with the low fracture resistance of concrete. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to propose a shrinkage models of VES-LMC (very-early strength latex-modified concrete) at early-age considering thermal deformation and autogenous shrinkage.

• 동력기계공학회지
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• 제13권6호
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• pp.76-81
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• 2009

Thermal desorption systems are designed to remove organic compounds from solid matrices such as soils, sludges and filter cakes without thermally destroying them. It is a separation technology, not a destruction technology. Since it is a thermal process, there is a common belief that temperature is the only significant parameter to be monitored. While it is true that better removal efficiencies are usually achieved at higher temperatures, other factors must be considered. Since the process is governed by mass transfer, heating time and the amount of mixing are also key parameters in optimizing removal efficiency. Thermal desorption have been successfully used for just about every organic contaminant found to date. It has also been used to remove mercury. In the present study, the numerical simulation has been performed to investigate the characteristics of heat transfer of LTTD(low temperature thermal desorption). The commercial software, AMESIM was applied for analyzing the heat transfer process in the LTTD.

• 한국정밀공학회지
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• 제28권8호
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• pp.894-903
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• 2011

In this paper, the capability index is introduced in order to improve the reliability of new concept machine tools and the method to improve the machine accuracy from the analysis of cutting process, statistical methodology and influence factors are proposed. In addition, the rib structure of bed and column in machine tools is analyzed by using the thermal impact method in order to analogize the rib pattern which has the small thermal deformation under thermal boundary condition. In the analysis of column rib structure, thermal boundary condition is separated to heat conduction and heat transfer to appropriate real boundary condition. Finally, performance chart of bed and column rib structure is provided for designer to estimate each rib pattern and select rib structure appropriating to thermal condition.

• 한국태양에너지학회 논문집
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• 제29권2호
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• pp.47-54
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• 2009

The amount of incident rays over inclination according to direction has been widely utilized as important data m installing solar thermal systems. To optimize the incident solar radiation, the slope, that is the angle between the plane surface in question and the horizontal, and the solar azimuth angles are needed for these solar thermal systems. This is because the performance of the solar thermal systems in much affected by angle and direction of incident rays. Recognizing that factors mentioned above are of importance, actual experiment on the moving route of the sun have been performed in this research to obtain the angle of inclination with which the maximum incident rays can be absorbed. After all, the standard for designing highly optimized solar thermal systems will be provided for designers and employees working in the solar collector related industries.

• 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 $2^{\circ}C/min$.

• 한국태양에너지학회 논문집
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• 제26권2호
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• pp.95-101
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• 2006

The purpose of this study is to present the simulation results and an overview of the performance assessment of the Ground-Source Heat Pump(GSHF) system. The calculation was performed for two design factors: the spacing between boreholes and the depth of the vertical ground heat exchangers. And the simulation was carried out using the thermal simulation code TRNSYS with new model of water to water heat pump developed by this study. As a result, it was anticipated that the yearly mean COPs of heat pump for heating and cooling are about 3.7 and 5.8 respectively and the heat pump can supply 100% of heating and cooling load all the year around.