• 한국기계가공학회지
• /
• 제18권3호
• /
• pp.33-40
• /
• 2019

FDM 3D printers have become widespread, and investment in the 3D printer industry is increasing. Therefore, many 3D printers are released and the functions of products are emphasized. However, to lower unit prices, open-type 3D printers are sold in kit form, and their performance is very low. If the 3D printer has many heat sources and is sealed, there is the possibility that the main accessories (the main board, power supply, and motor) will be damaged by trapped heat. At the same time, if the ambient temperature is low due to the properties of the material, the output quality deteriorates. In this study, we analyzed the temperature rise of the main accessories and the quality of the output by the heat bed when a chamber was added to an open-type 3D printer. We also compared the quality of the output due to the air flow with the temperature rise of the main accessories. Moreover, we found the optimal value. As a result of the quality analysis, it was finally confirmed that the case with the chamber at $95^{\circ}C$ was the best for the printing condition. In addition, in the absence of the chamber, the bending of the specimen was found to be large, and in the case of the chamber, the degree of bending was slightly decreased by 0.05 mm.

• 대한기계학회논문집B
• /
• 제38권6호
• /
• pp.475-482
• /
• 2014

본 연구는 스프레이 열전달을 이용한 저온도차 스털링 엔진의 실험적 개념 연구를 제시한다. 스프레이 열교환기는 노즐을 통하여 엔진 작동 공간에 직접 물을 분사함으로써 엔진 성능을 저해하는 불용 공간을 최소화하고 열전달 효율을 높였다. 직접 구현된 실험 스털링 엔진의 실증 실험은 운전 시점의 기동 특성, 정상 상태의 운전 특성, 엔진의 출력 특성에 대하여 진행하였다. 실험 결과, 열수 유량 증가에 대하여 엔진 기동 시 작동 최소 온도는 감소한 반면, 고온부 온도와 고온부-저온부 온도차는 대체로 일정하였다. 정상 상태 운전의 경우 열수 온도 및 유량 증가에 대하여 작동 주파수는 증가하였다. 엔진 출력은 열수 온도 및 유량 증가에 따라 사이클당 일 및 작동 주파수 증가로 인하여 증가하였다. 본 연구에서 구현된 실험 스털링 엔진은 열수 유량 30 ml/min, 열수 온도 $65^{\circ}C$, 고온부-저온부 온도차 $6^{\circ}C$ 이상에서 엔진 출력 0.05W 수준으로 안정된 기동 및 운전 특성을 보였으며, 향후 출력 증가 및 다양한 적용 연구를 지속할 계획이다.

• 대한소아치과학회지
• /
• 제31권1호
• /
• pp.85-91
• /
• 2004

연구목적은 복합레진 중합 광원에 따른 치수강 온도 변화를 관찰하는 것이었다. 연구에 사용된 광중합기는 일반 플라즈마아크 광중합기, 저발열 플라즈마 아크 광중합기, 저출력 할로겐 광중합기, 저출력 LED 광중합기, 고출력 LED 광중합기의 다섯 개이었다. K-type thermocouple 온도계를 사용하여, 중합기 light guide tip에서의 온도를 측정하고, 잔존 상아질 두께가 1mm가 되도록 형성한 유구치 와동에 상아질 접착제만 도포한 군, ionomer glass를 함유한 base 또는 calcium hydroxide를 함유한 base를 0.5mm두께로 이장한 군에서 각각 레진 충전 전과 후의 치수강내 온도를 측정하였다. 중합기 light guide tip에서 측정한 온도는 일반 플라즈마가 $52.94^{\circ}C$로 가장 높았고, 저출력 LED가 $26.14^{\circ}C$로서 가장 낮았다. 레진충전 전의 치수강내 온도는 고출력 LED가 $41.60{\sim}43.34^{\circ}C$로 가장 높았고, 저출력 LED는 $36.50{\sim}36.76^{\circ}C$로서 가장 낮았다. 레진 충전 후의 치수강내 온도는 고출력 LED가 $40.22{\sim}40.94^{\circ}C$로 가장 높았고, 저발열 플라즈마와 저출력 LED는 온도 상승이 없었다. Base의 사용은 부분적인 열 차단 효과가 있었다.

• KIEAE Journal
• /
• 제10권6호
• /
• pp.27-32
• /
• 2010

Approximately 20 percentage of energy consumptions in buildings is consumed as lighting energy. Thus, most of the corporations of lighting fixture have launched low energy products. However, many researchers focused on the only luminous efficacy for energy conservation and used the evaluating tool of study. This can not gauge the precise cooling load related on generated heat of artificial lighting. In order to assess an effect of the temperature variation of lighting resources, the main purpose of this study is to predict the generated heating energy from lighting by measuring the thermal variation in scale model to reduce external noise. Also this paper used MX100 data logger to record at an interval of 1 minute for 60 minutes for the temperature of interior lightings such as incandescent lamp, fluorescent light, halogen lamp and LED lamp. As a result, LED lamp generated the lowest heat. On the other hand, incandescent lamp did the highest.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.315-318
• /
• 2009

Hydrogen is the ideal candidate as an alternative energy carrier, so many hydrogen storage methods are investigated. The hydrogen storage method using metal hydride is good candidate as energy sources for portable devices because hydrogen-storage as metal hydride shows large volumetric storage density. In this study, we investigated the variations of hydrogen charging/discharging performance of metal hydride tanks at different temperature conditions. We charged metal hydride tanks with hydrogen in low temperature because of the exothermic reactions of hydrogen absorption while we discharged in high temperature to provide sufficient heat because of the endothermic reactions of desorption. In addition, we investigated the difference of hydrogen charging/discharging performance between two tanks having different sizes.

• 대한기계학회논문집B
• /
• 제37권12호
• /
• pp.1137-1145
• /
• 2013

본 연구에서는 열 구동 냉동사이클로서 유기 랭킨사이클 (ORC)과 증기 압축 냉동사이클(VCC)의 복합 사이클에 대한 엑서지 해석을 수행하였다. 시스템의 열원으로는 다양한 재생 에너지 열원이나 산업체에서의 폐열 등 현열 형태의 저온 열원을 고려하였으며 작동유체로서 R143a, R22, R134a, 프로판, 이소부탄, 부탄, R245fa 및 R123 등 여덟가지 작동유체들을 고려하였다. 터빈 입구 압력의 변화나 작동유체의 종류에 따라 시스템의 COP 나 엑서지 효율은 물론 시스템의 각 요소에서의 엑서지 파괴 (아너지)에 미치는 다양한 영향에 대해 분석하고 논의하였다. 해석 결과는 주어진 열원 온도에 대해 시스템에서 가장 엑서지 파괴가 큰 구성 요소는 터빈 입구 압력과 작동유체에 따라 민감하게 변화하는 사실을 보여준다.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.782-787
• /
• 2008

The Kalina cycle simulation study was carried out for a preliminary design of a geothermal power generation system. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The simulation results show that the power generation efficiency over 10% is expected when a heat source and sink inlet temperatures are $100^{\circ}C$ and $10^{\circ}C$ respectively.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2012년도 전기공동학술대회 논문집
• /
• pp.280-280
• /
• 2012

DME(Dimethyl Ether) is the one of the massive energy sources synthesized from natural gas. KOGAS has already developed the commercial-scale production plant of DME and has been doing to obtain overseas resources to meet the domestic needs. This paper presents an experimental study on the evaporation phenomena of DME in FPSO or cargo vessel. The various moving motions, along with heat intake cause the evaporation of low temperature liquids in vessel's storage tank. The experimental result shows that the evaporation rate was changed with rolling degree and cycle and liquid level. The rolling motion leads to evaporate about 30~35% of total evaporation quantity and the rest amount from heat intake.

• 한국산업보건학회지
• /
• 제15권3호
• /
• pp.239-249
• /
• 2005

Ventilation effect is analyzed for boiler building with multiple heat sources. Air flow inside the boiler building is characterized as turbulent mixed convection. Analysis methodology is set up with two different $k-{\varepsilon}$ type models (standard $k-{\varepsilon}$, RNG $k-{\varepsilon}$). Two different cases with high and low outside temperature are analyzed. In case of high outside temperature condition, mixed convection is well realized inside the boiler building. With different upper louver opening rate, air flow is also well established and proper opening rate is found to meet design limit in case of low outside temperature condition. Difference of analysis results for two different turbulence models are not significant. Therefore, analysis methodology with simple $k-{\varepsilon}$ turbulence model is found to be reliable for the boiler building ventilation analysis. However, more simplified geometrical model is desired to expand its application.

• 한국유체기계학회 논문집
• /
• 제18권4호
• /
• pp.13-21
• /
• 2015

The system design of the Organic Rankine Cycle(ORC) is greatly influenced by the thermal properties such as the temperature or the thermal capacity of heat source. Typically waste heat, solar energy, geothermal energy, and so on are used as the heat source for the ORC. However, thermal energy supplying from these kinds of heat sources cannot be provided constantly. Hence, an experimental study was conducted to utilize fluctuating thermal energy efficiently. For this experiment, an impulse turbine and supersonic nozzles were applied and the supersonic nozzle was used to increase the velocity at the nozzle exit. In addition, these nozzles were used to adjust the mass flowrate depending on the amount of the supplied thermal energy. The experiment was conducted with maximum three nozzles due to the capacity of thermal energy. The experimented results were compared with the predicted results. The experiment showed that the useful output power could be producted from low-grade thermal energy as well as fluctuating thermal energy.