• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.70-77
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• 2013

Recently the radiant panel heating and cooling system has been regarded as an alternative of low temperature heating and high temperature cooling by applying the renewable energy sources to the heating and cooling of buildings. Especially this system can be used as HVAC system alternatives in super high-rise buildings for energy saving and thermal comfort. Also it can be possible to reduce the plenum space because the minimum ventilation air will be supplied into the space. This study focused on the evaluation the basic characteristics of thermal output in prefabricated steel wall panel system for radiant heating and cooling. In order to evaluate the thermal output according to both various supply water temperatures and supply water flow rates, three-dimensional dynamic heat transfer analysis was performed. As results, for the heating mode, thermal output increased by 26% with the supply temperature increasing by $5^{\circ}C$. The surface temperature of panels range within $1{\sim}3^{\circ}C$. For the cooling mode, thermal output decreased by 18.2% with the supply temperature increasing by $2^{\circ}C$. The surface temperature of panels range within $0.5{\sim}1^{\circ}C$ and it was shown the even temperature distribution.

• 한국기계가공학회지
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• 제19권6호
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• pp.36-42
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• 2020

Nowadays, the touch screen panel (TSP) cover glass for mobile smart devices is being developed with a curved glass shape due to different design requirements. Because the sizes of mobile smart devices continue to increase, there has also been a great increase in the demand for large-area curved glass greater than 20 inches. In this study, heat and fluid flow analysis using CFD was performed to optimize the heating surface temperature distribution of the large curved glass formation system. Five cooling water flow paths in the cooling block were designed and analyzed for each case. A function that can quantitatively calculate the temperature uniformity of the heating surface was proposed and these values were obtained for the five models. The temperature distributions of the heating surface and the energy consumption of the heating system were also compared and comprehensively analyzed. Based on the analysis results of the five different cooling channel path models, the optimal path design could be presented.

• 한국재료학회지
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• 제27권11호
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• pp.636-642
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• 2017

In the present study the microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes was characterized and identified based on various microstructure analysis methods including optical and scanning electron microscopy, and electron backscatter diffraction(EBSD). Although low-carbon steels are usually composed of ${\alpha}-ferrite$ and cementite($Fe_3C$) phases, they can have complex microstructures consisting of ferrites with different size, morphology, and dislocation density, and secondary phases dependent on rolling and accelerated cooling conditions. The microstructure of low-carbon steels investigated in this study was basically classified into polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite based on the inverse pole figure, image quality, grain boundary, kernel average misorientation(KAM), and grain orientation spread(GOS) maps, obtained from EBSD analysis. From these results, it can be said that the EBSD analysis provides a valuable tool to identify and quantify the complex microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.275-280
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• 1999

It was analysed the effect of pipe cooling as a measure to avoid thermal cracks due to the heat of hydration during the curing process of a massive prestressed concrete (PSC) slab. PSC slab has a complex three-dimensional shape of which the maximal and minimal thicknesses of cross-section were 2.8 and 0.95m, respectively. Steel pipes of which the diameter was 1 inch were employed for cooling. The horizontal and vertical distances between the contiguous pipes were 0.5 and 0.6m, respectively. One the four layers of cooling pipe were arranged according to the thickness of cross-section. Temperature distribution was calculated by the program developed by the authors, of which the accuracy was verified on a few published papers by the authors. Based on the temperature analysis of the cross-section which had four layers of cooing pipe, the maximum temperature of concrete interior was 54.2$^{\circ}C$ and the maximum differenced between the interior and surface temperatures of concrete was 14.$0^{\circ}C$ and, thereby, the thermal cracking index was 1.1. Upon the stress analysis, the thermal cracking index was 0.92 and the probability of thermal-crack development was 52%. Therefore, it was expected to make it possible to reduce the probability of thermal-crack development in a massive PSC slab by adopting pipe cooling.

• 한국기계가공학회지
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• 제11권2호
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• pp.105-111
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• 2012

High speed machining is the core technology that influences the performance of machine tools, and the high speed motor spindle is widely used for the high speed machine tools. The important problem in high speed spindle is to minimize the thermal effect by motor and bearing and frequency effect. This paper presents the thermal characteristic analysis and frequency experiment for a high speed spindle considering the flow rate of cooling oil. A high speed spindle is composed of angular contact ceramic ball bearings, high speed built-in motor, oil cooling jacket and so on. The thermal analyses of high speed spindle need to minimize the thermal effect and maximize the cooling effect and they are carried out under the various cooling conditions. Heat generations of the bearing and the high speed motor are estimated from the theoretical and experimental data. To find out the characteristic of vibration, the high speed spindle is excited in operational range. This result can be applied to the design and manufacture of a high speed tapping spindle.

• 한국추진공학회지
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• 제17권3호
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• pp.67-75
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• 2013

케로신-액체산소 로켓 엔진에 적용되는 산화제 과잉 예연소기의 냉각 성능 확인을 위한 수치 해석을 수행하였다. 예연소기 1차 연소구역을 상사하기 위하여 분사기 배열에 따른 혼합비를 바탕으로 연소가스 물성치를 계산하였고, 냉각제로서 채널을 흐르는 산소의 물성치는 실제기체 조건에 대하여 적용하였으며, 1차 연소구역과 냉각제로 쓰인 액체산소의 혼합과정은 다상혼합모델을 적용하였다. 수치 해석으로 계산된 결과를 연소시험과 비교하였으며, 이를 통하여 재생냉각 채널과 연소실에서의 물성 등을 정량적으로 파악할 수 있었다.

• 설비공학논문집
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• 제15권10호
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• pp.879-887
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• 2003

Buildings with heating and cooling systems have been increased, since the requirement of thermal comfort for residents is grown. Heating and cooling systems, have been changed from two separate systems to one multi-function system which includes both heating and cooling. Especially, heat pump heating and cooling system has been adopted for general classrooms in schools since education environment improvement project has been launched. This research suggests the best option for the heat pump heating and cooling system in educational buildings through economic assessments for four alternative systems based on electric heat pump (EHP) and gas engine driven heat pump (GHP), which are most widely used for elementary, middle and high schools. The model buildings are in the Y high school which has 24 classes of new construction building, which will be built soon. Annual energy consumption for alternative systems uses BECS 3.10, which can be used for system simulation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2750-2753
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• 2008

This paper introduce the CFD analysis for predicting the heat transfer at the Ultrasonic horn. Approximately Ultrasonic horn separates two part. One is preheating part and the other is cooling part. Temperature of preheating part rise up by $260^{\circ}C$ that make it possible to attach a chip to a semiconductor. Also there is a piezo material in the cooling part. When piezo work, it generates heat of $100^{\circ}C$. It can stand by $150^{\circ}C$. But the high temperature conducted from the preheating part has a bad affect on the piezo. These situation make it necessary cooling at piezo. Previously except of the piezo, all of them are composed of the SUS440c that has good thermal conductivity. This study shows way that not only cooling the piezo but also cutting off the conduction between preheating part and cooling part by using the Ti and Duralumin that have low thermal conductivity compare with the SUS440c. Conclusion of CFD analysis that the heat coming from the piezo can't be transferred the horn cause of the Ti and Duralumin.

• 콘크리트학회논문집
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• 제26권1호
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• pp.57-62
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• 2014

이 연구에서는 수직으로 긴 매스 구조물에 적합한 파이프쿨링 공법을 제안하기 위하여 기존의 파이프쿨링 공법과는 달리 파이프를 수직으로 설치하는 연직파이프쿨링 공법을 개발하였다. 타당성을 검토하기 위하여 해석대상 부재의 형상($1{\times}3{\times}20m$, $4{\times}4{\times}4m$)을 대상으로 하여 FEM 해석을 수행하였으며, 온도 및 응력 변화와 온도균열 지수 등을 검토하였다. 그 결과, 매스콘크리트 구조물의 온도균열 제어에 효과가 있는 것을 확인할 수 있었다.

• 한국추진공학회지
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• 제16권5호
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• pp.37-46
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• 2012

로켓엔진 연소실에서 막냉각을 고려한 열전달 해석을 위한 모델을 수립하였다. 연소실 내에서의 대류, 복사, 막냉각 효과는 로켓엔진을 위한 경험식을 사용하였으며, 벽 외부는 일반적인 대류, 복사 식을 적용하였다. 또한 벽 내부는 유한체적의 격자를 구성하여 시간전진법에 의해 비정상 열해석을 수행하였다. 연소압 50 기압의 액체산소/케로신 엔진을 예로 해석하였으며, 이 경우 4% 유량의 막냉각까지는 벽온도를 낮추는데 크게 기여하였으나, 그 이상의 공급은 막냉각 유량에 비해 효과가 미비함을 확인하였다.