• Journal of Advanced Marine Engineering and Technology
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• 제35권2호
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• pp.189-195
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• 2011

본 논문은 R744-R404A용 캐스케이드 냉동시스템의 기초 설계자료를 제공하기 위해서 COP 예측 상관식을 제안하고 그 결과를 타 상관식과 비교하였다. 작동변수로는 R404A용 고온사이클과 R744용 저온사이클의 과냉각도와 과열도, 압축기효율, 응축과 증발온도이다. 이에 대한 주요결과를 요약하면 다음과 같다. 다중회귀 분석을 통해 R744-R404A용 캐스케이드 냉동시스템의 성능 예측식을 제안하였고, 그 결과를 타 연구자들의 상관식과 비교하였다. 그 결과 본 연구에서 제안한 성능 예측식은 타 연구자들의 상관식과 일치하지 않았다. 따라서 향후 R744-R404A용 캐스케이드 냉동시스템에 대한 추가 실험 데이터와 본 연구에서 제안한 COP 예측 상관식을 비교하여 그 신뢰성을 확보할 필요가 있다.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.666-671
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• 2014

최근 디젤 차량과 같은 내연기관의 고효율화에 따라, 보조난방 열원으로서 PTC 히터의 사용이 증가하는 추세이다. 디젤 차량의 시동 초기에는 냉각수의 온도가 난방으로 직접 사용하기에 충분히 높지 않으므로, 동절기 난방을 위해 보조난방 열원은 필수적이다. 본 연구에서는 스크린 인쇄 전극공정을 바탕으로 한 PTC 소자를 제작하였고, 이를 활용한 PTC 소자 모듈 및 히터를 설계 및 제작하였다. PTC 소자 모듈의 방열핀 접촉형상 및 전열소자의 크기 변경에 따른 난방성능 변화를 열유동 해석을 통해 분석하였고, 난방성능 실험을 수행하여 PTC 히터의 난방성능 및 효율 특성을 살펴보았다. PTC 히터 시작품의 경우, 기존 PTC 히터와 동등한 수준 이상의 난방성능 및 효율을 나타내었으며, 향후 이를 바탕으로 PTC 소자와 히터에 대한 공정개선 및 성능증대 연구를 수행할 계획이다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.53-53
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• 2018

Thermoelectric materials can convert directly waste heat to electricity and vice versa. The improvement of the thermoelectric efficiency strongly depends on the dimensionless figure of merit, $ZT=S^2{\sigma}T/{\kappa}$, where S is the Seebeck coefficient, ${\sigma}$ is the electrical conductivity, T is the absolute temperature, and ${\kappa}$ is the thermal conductivity. The thermal conductivity consists of the electronic contribution (${\kappa}_e$) and phonon contribution (${\kappa}_{ph}$). It is very challenge to increase the power factor, $S^2{\sigma}$ and to reduce the thermal conductivity simultaneously because the power factor and electronic thermal conductivity are coupled. One strategy is to decrease the phonon thermal conductivity. The phonon thermal conductivity can be decreased by controlling the grain size and structural defects such as dislocations and twinning. In order to achieve enhancements in thermoelectric efficiency, microstructures that can form numerous interfaces have been investigated intensively for controlling the transport of charge carriers and heat carrying phonons. In this presentation, we report the heterogeneous microstructure of $Mg_2Si_{0.6}Sn_{0.4}$ thermoelectric materials and investigation of its influence on thermoelectric properties.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.58-63
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• 2014

A vertical closed loop ground source heat pump (GSHP) is used to produce heat from the low-grade energy source such as the outside air and ground source. It is known that a heat pump system type has better efficiency comparing to the electric heating system. This study only demonstrates that the vertical closed loop GSHP system is a feasible choice for space cooling of air conditioning. The coefficient of performance (COP) is the ratio of heat output to work supplied to the system in the form of electricity. For the vertical closed loop GSHP system in a cooling mode, the COP is the most commonly used way for judging the efficiency. For the purpose of this experiment, vertical closed loop GSHP system was installed in the laboratory and the experiment was executed. As a result, an average COP of vertical-closed loop GSHP system was 3.62 when the outside average temperature was $33^{\circ}C$.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.281-285
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• 2008

Effective use of available energy sources is of general concern along with the issues of global warming and unstable oil price. As one of the effort to recover waste heat from industrial facilities effectively, researchers have interest in a technology called organic Rankine cycle(ORC), in which the working fluid is some organic liquid instead of water. Known to have poor efficiency already, this old technology is considered to give an innovative solution to utilizing low grade energy sources, by improving the efficiency. Nano fluidics, coatings and the use of additives are the examples of these efforts. In the present study, we present simulated performance of a horizontal tube type condenser geometry. N-hexanr and isopentane are compared to water vapor case under 1 atm and the inet cooling water temperature of $20^{\circ}C$. EES(Engineering Equations Solver) is used for the present work.

• Current Photovoltaic Research
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• 제12권2호
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• pp.41-47
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• 2024

CIGS solar cells are thin film solar cells that have excellent light absorption coefficient and can be manufactured with high efficiency through the use of low materials. In Korea, they must pass KS certification for home and commercial installation. KS C 8562 is a standard for evaluating the durability of CIGS and thin film amorphous silicon solar modules and deals with contents such as light, temperature, humidity, and mechanical durability. Unlike general crystalline silicon solar modules, the CIGS solar module has a different behavior of output change through these environmental tests, so if it shows 90% or more of the rated output suggested by the manufacturer after the final test, it is judged to be a suitable product. In this paper, the output before and after individual tests was measured through the test method of KS C 8562 to observe the output change and to discover the vulnerabilities of the CIGS solar module when exposed to various environments. Through this, it was confirmed that humidity exposure was the most vulnerable and that it had output recovery characteristics for light (visible light and ultraviolet rays). This study attempted to present the output behavior characteristics and data of the CIGS module at the time when the high efficiency thin film photovoltaic module market is expected to be created in the future.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.768-773
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• 2009

A numerical study has been performed to investigate the thermal Performance of Solar heating system with baffle type of storage tank by using the commercial code TRNSYS. As a result, the solar fraction depends strongly on the efficiency and heat loss coefficient of solar collector as well as the heating capacity of house and the water temperature supplied to the shower. In addition, the solar fraction has been basically ranked to higher level in baffle type of storage tank than typical type of single storage tank for the range of operation condition.

• Journal of Microbiology and Biotechnology
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• 제9권3호
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• pp.297-302
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• 1999

Simultaneous saccharification and fermentation (SSF) experiments were carried out with a lignocellulosic biomass. The effects of temperature on enzymatic saccharification and the ethanol fermentation were also investigated. The batch SSF process gave a final ethanol concentration of 10.44 g/l and equivalent glucose yield of 0.55 g/g, which was increased by 67％ or higher over the saccharification at 42℃. The optimal operating condition was found to vary in several parameters, such as the transmembrane pressure, permeation rate, and separation coefficient, related to the SSF combined with membrane system (semi-batch system). When the fermentation was operated in a semi-batch mode, the efficiency of the enzymes and yeast lasted three times longer than in a batch mode.

• Journal of Biosystems Engineering
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• 제19권3호
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• pp.222-231
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• 1994

The efficient use of solar energy for greenhouse heating is one of the most obvious applications to save the heating energy for greenhouse culture. To increase the efficiency of solar energy utilization in plastic greenhouse, underground heat exchange system was installed. Characteristics of the stored and released thermal enery in plastic greenhouse with underground heat exchange system was analyzed. The average stored and released thermal energy in this system were 1,484 $kJ/m^2$ day and 555 $kJ/m^2$ day, respectively. The average coefficient of performance of heat exchange system was found to be 2.86. Also an attempt was made to predict the air temperature in plastic greenhouse. The agreement between the results of prediction and that of measurement was relatively good.

• 설비공학논문집
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• 제22권11호
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• pp.805-811
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• 2010

A numerical study has been performed to investigate the thermal performance of solar heating system with baffle type of storage tank by using the commercial code TRNSYS. As a result, the solar fraction depends strongly on the efficiency and heat loss coefficient of solar collector as well as the heating capacity of house and the water temperature supplied to the shower. In addition, the solar fraction has been basically ranked to higher level in baffle type of storage tank than typical type of single storage tank for the range of operation condition.