• 한국환경과학회지
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• 제15권5호
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• pp.493-501
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• 2006

The increase in environmental loads and energy consumptions has resulted in the need of developed new forms of energy for a sustainable use for the society. Recently, the viability of using unused energy has attracted a great deal of attention. From the view point of using unused energy, the most critical problem can be referred to as the distance between the heat source/sink and heat demand area. The water resource in the city water system was used to solve this distance problem with unused energy. The calculation method of the potential use unit was used to survey the potential of the water resource in the city water system. The amount of theoretical unused energy and energy savings in the model city were estimated using this method. It is estimated that the amounts of energy savings and $CO_2$ reduction correspond to 131.3 GWh and 29280[t-C], respectively, per annual basis.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.635-640
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• 2000

Thermal deformation of machine tools can be evaluated from the analysis of the whole temperature field. However, it is extremely inefficient and impossible to acquire the whole temperature field by measuring temperatures of every point. So, a temperature estimator, which can estimate the whole temperature field from the temperatures of just a few points, is required. In this paper, 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. and then state observer is designed to estimate the intensity of heat source and the whole temperature field in real-time. The reliability of this estimator is verified by making a comparison between solutions by the proposed method and the exact solutions of examples. The proposed method is applied to the estimation of temperature distribution in a ball screw system.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.161-164
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• 2009

This research is to show the mechanical properties of structural steels by welding at high temperature. Welding parts are divided with weld metal and HAZ(Heat Affected Zone). HAZ is formed by interval from welding heat source and heating and cooling rates. Then, the change of both microstructure and mechanical properties occurs. Discontinuity of mechanical and chemical property at HAZ is the cause of safety decrease of structure. At this point, in this research, tensile tests at high temperature with test pieces of base metal and weld metal of SS400 and SM490 are accomplished. From the results, the mechanical properties of both SS400 and SM490 are standardized without welding or non-welding.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.1044-1051
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• 2005

The isothermal characteristics of a rectangular parallelepiped sodium heat pipe were inves­tigated for high-temperature applications. The heat pipes was made of stainless steel of which the dimension was $140\;m\;(L)\;{\times}\;95m\;(W)\;{\times}\;46 m\;(H)$ and the thickness of the container was 5 mm. Both inner surfaces of evaporator and condenser were covered with screen meshes to help spread the liquid state working fluid. To provide additional path for the working fluid, a lattice structure covered with screen mesh wick was inserted in the heat pipe. The bottom surface of the heat pipe was heated by an electric heater and the top surface was cooled by circulating coolant. The concern in this study was to enhance the temperature uniformity at the bottom surface of the heat pipe while an uneven heat source up to 900 W was in contact. The temperature distribution over the bottom surface was monitored at more than twenty six locations. It was found that the operating performance of the sodium heat pipe was critically affected by the inner wall temperature of the condenser region where the working fluid may be changed to a solid phase unless the temperature was higher than its melting point. The maximum temperature difference across the bottom surface was observed to be $114^{\circ}C$ for 850 W thermal load and $100^{\circ}C$ coolant inlet temperature. The effects of fill charge ratio, coolant inlet temperature and operating temperature on thermal performance of heat pipe were analyzed and discussed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.95-99
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• 1994

Robot engineering is developed mainly in the field of intelligibility such as a manipulation. Considering the popularization of robots in the future, however, a robot should be studied from a viewpoint of saving energy because a robot is a kind of machine with a energy conversion. This paper deals with minimizing an energy consumption of a manipulator which is driven in a point-to-point control method. When a manipulator carries a heavy payload toward gravitation or the links are de-accelerated for positioning, the motors at joints generate electric energy. Since this energy can be regenerated to the source by using a chopper, the energy consumption of a manipulator is only heat loss by an electric and a frictional resistance of the motors. The minimization of the sum of these losses is reduced Lo a two-points boundary-value problem of an non-linear differential equation. The solutions are obtained by the generalized Newton-Raphson method in this paper. The energy consumption due to the optimum angular velocity patterns of two joints of a two-links manipulator is compared with conventional velocity patterns such as quadratic and trapezoid.

• 한국방재학회 논문집
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• 제10권6호
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• pp.59-64
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• 2010

산불 지표화의 방화선 구축작업은 낙엽 및 관목류 등 지표 연료층을 제거함으로써 화염전파를 차단하는 대표적인 간접진화방법이다. 화재역학적인 의미의 방화선 구축은 화염으로부터 방출되는 열전달에너지에 미연소 연료가 착화되지 않도록 열전달 차단 구간을 설정하는 작업이다. 본 연구에서는 소나무 낙엽층에 대해 복사열전달 점열원 모델을 이용하여 풍속, 경사별로 지표화 화염을 방지할 수 있는 방화선 구축 폭 산정 방법을 제시하였고 평가를 실시하였다. 방화선 구축 폭은 소나무 낙엽 착화 임계 복사열유속인 $4.9\;kW/m^2$가 미치는 거리를 기준으로 평가하였다. 그 결과, 풍속 0~5 m/s, 경사 $0{\sim}50^{\circ}$ 조건에서의 방화선 구축 폭은 평균 화염 기준의 경우, 0.35~0.65 m, 최대 화염높이 기준의 경우, 0.75~1.05m로 산정되었다. 따라서 안전율을 고려한 적정 방화선 구축 폭은 최대 화염 높이를 적용한 1.05 m가 적합할 것으로 판단되며 향후, 실험 및 현장사례조사를 통하여 지표층 연료별 적정 방화선 구축 폭에 대한 비교분석 연구가 추가적으로 필요할 것으로 판단된다.

• Design & Manufacturing
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• 제16권4호
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• pp.34-39
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• 2022

Sustained economic development around the world is accelerating resource depletion. Research and development of secondary batteries that can replace them is also being actively conducted. Secondary batteries are emerging as a key technology for carbon neutrality. The core of an electric vehicle is the battery (secondary battery). Therefore, in this study, the temperature change by the heat source of the hammer and the rotational speed (rpm) of the abrasive disc of the Classifier Separator Mill (CSM) was repeatedly calculated and analyzed using the heat flow simulation STAR-CCM+. As the rotational speed (rpm) of the abrasive disk increases, the convergence condition of the iteration increases. Under the condition that the inlet speed of the Classifier Separator Mill (CSM) and the heat source value of the disc hammer are the same, the disc rotation speed (rpm) and the hammer temperature are inversely proportional. As the rotational speed (rpm) of the disc increases, the hammer temperature decreases. However, since the wear rate of the secondary battery material increases due to the strong impact of the crushing rotational force, it is determined that an appropriate rpm setting is necessary. In CSM (Classifier Separator Mill), it is judged that the flow rate difference is not significantly different in the direction of the pressure outlet (Outlet 1) right above the classifier wheel with the fastest flow rate. Because the disc and hammer attachment technology is adhesive, the attachment point may deform when the temperature of the hammer rises. Therefore, it is considered necessary to develop high-performance adhesives and other adhesive technologies.

• 한국연소학회지
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• 제20권4호
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• pp.10-18
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• 2015

Combustion instability is a major issue in design and maintenance of gas turbine combustors for efficient operation with low emissions. With the thermoacoustic view point the instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to study the combustion dynamics of gas turbine combustors, Morgans et al (2014) have developed OSCILOS (open source combustion instability low order simulator) code and it is currently available online. In this study the code has been utilized to predict the combustion instability of a reported case for lean premixed gas turbine combustion, and then its prediction results have been compared with the corresponding experimental data. It turned out that both the predicted and the experimental combustion instability results agree well. Further the effects of some typical inlet acoustic boundary conditions on the prediction have been investigated briefly. It is believed that the validity and effectiveness of the open source code is reconfirmed through this benchmark test.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.81-82
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• 2007

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C\;and\;420^{\circ}C$, respectively. After the as-grown single crystal $CdGa_2Se_4$ thin films were annealed in Cd-, Se-, and Ga -atmospheres, the origin of point defects of single crystal $CdGa_2Se_4$ thin films has been investigated by PL at 10 K. The native defects of $V_{Cd},\;V_{Se},\;Cd_{int},\;and\;Se_{int}$ obtained by PL measurements were classified as donors or acceptors. And we concluded that the heat-treatment in the Cd-atmosphere converted single crystal $CdGa_2Se_4$ thin films to an optical p-type. Also, we confirmed that Ga in $CdGa_2Se_4$/GaAs did not form the native defects because Ga in single crystal $CdGa_2Se_4$ thin films existed in the form of stable bonds.

• 대한기계학회논문집 C: 기술과 교육
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• 제4권1호
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• pp.3-10
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• 2016

국내 히트펌프 유닛에 대한 성능 기준은 KS C 9306에서 제시하는 표준조건에서의 COP로 표현된다. 그러나 히트펌프 시스템이 실제 건물에 적용될 경우에는 표준조건에서 운전되는 것이 아니기 때문에 현장의 기후 조건, 건물의 특성에 따라 히트펌프 시스템의 성능은 다르게 나타난다. 본 논문에서는 주거건물을 대상으로 국내 주요 도시의 기후 조건에 따른 공기 대 공기 히트펌프 시스템의 연성능을 평가하여 기존의 BIN 데이터를 활용한 연성능 평가 결과와 정량적으로 비교 분석하였다. 연성능 평가도구로는 IPMVP 4.4.2에서 제시한 국제호환형 프로그램인 TRNSYS를 사용하였다. 공기 대 공기 히트펌프 유닛의 멀티 성능 데이터를 적용한 경우, 연성능 평가 기준인 APF는 BIN 데이터를 적용했을 때보다 전체적으로 높았으며, 부산이 2.36으로 가장 높았고, 대전이 2.29로 가장 낮았다.