• Journal of Biosystems Engineering
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• 제27권1호
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• pp.39-44
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• 2002

In order to obtain the information of bio-environment control, the thermal characteristics of soil in the greenhouse heated by the heat pump and latent heat storage system were experimentally analyzed. The experimental systems were composed of the greenhouse with a heat pump and a latent heat storage system (system I), the greenhouse with a heat pump (system II), the greenhouse with a latent heat storage system (system III), and the greenhouse without auxiliary heating system (system IV). The thermal characteristics experimentally analyzed in each system were temperature of soil layers, soil heat storage and release, soil heat capacity and soil heat storage ratio. The results could be summarized as follows. 1. Time to reach the highest temperature at 20cm deep in soil layers of the crop routs in case of system I was shown to be delayed by 6 hours in comparison to the time of the highest temperature at the soil surface. 2. In the clear winter days, the stored heat capacity values fur the system I and the system II were shown to be 22.3% and 11.0% higher than the released heat capacity respectively, and the stored heat capacity values for the system III and the system IV were shown to be 6.2% and 29.6% lower than the released heat capacity respectively This confirms that the system I provided the best heat storage effect. j. The heat quantity values stored or released were shown to be highest at 5 cm depth of soil layers. And it was reduced with increasing of depth of soil layers until 20 cm and was not changed under the soil layer of 20 cm depth. 4. The heat absorption rates of soil, the ratio between supplied and stored heat energy, fur both the system I and system II were lower than 23%.

• 한국산학기술학회논문지
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• 제15권8호
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• pp.4749-4755
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• 2014

본 연구는 고용량 인버터 등의 열 발생 환경에서 히트싱크의 방열성능을 극대화하기 위한 파라미터 연구의 일환으로 히트싱크 베이스 두께 변화에 대한 방열성능 변화를 조사하였다. 베이스 두께가 각각 5, 9.5 및 14 mm인 히트싱크의 방열성능을 히트싱크 베이스의 윗면 중앙 온도, 히트싱크를 통한 방열량 및 열원부의 온도 등의 세 가지 지표의 비교를 통하여 고찰하였다. 실험연구와 전산유체역학 프로그램을 이용한 해석연구를 병행하여 베이스 두께 변화에 따른 각 방열 성능 지표에 변화가 있음을 확인하였다. 베이스의 윗면 중앙 온도와 방열율은 베이스의 두께가 얇을수록 향상되는 효과를 보였고, 베이스 열원부의 온도는 베이스의 두께가 두꺼울수록 낮아지는 경향을 보였다. 성능 지표의 비교 고찰을 통해 연구에 사용된 세 히트싱크 내에서는 베이스의 두께가 9.5 mm인 히트싱크에서 최적점이 나타났다. 따라서 제한적이지만 본 연구결과 내에서는 9.5 mm 두께의 베이스를 가지는 히트싱크가 최적의 방열 성능을 보이는 것으로 판단되었다.

• 접착 및 계면
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• 제14권3호
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• pp.135-145
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• 2013

환경친화형 반도체 봉지재로서 할로겐 화합물 등의 첨가형 난연제를 혼합하지 않고 자기소화성을 발현시키는 에폭시수지 조성물에 관해 연구하였다. 탄화수소계 방향족 공액이중결합의 구조를 갖는 에폭시수지와 페놀수지의 반응물에서 자기소화성을 갖는 낮은 연소열이 확인되었다. 본 연구에서는 탄화수소계 방향족 공액이중결합에 헤테로원자계 이중결합인 아조메틴기를 도입하여 더욱 낮은 연소열을 확인할 수 있었다. 낮은 연소열의 결과는 높은 반응열과 열전이온도 그리고 빠른 반응성과 관련이 있으며 아조메틴기의 헤테로원자 구조의 영향 때문으로 보인다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.545-548
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• 2005

There is a close relation between the heat generation in the fuel cell stack and the fuel cell performance. In PEM fuel Gell vehicles, the stack coolant temperature is about $65^{\circ}C$, which is far lower than that for general automobile engine. Therefore, it is hard to release heat generated in the stack by using a radiator of limited size because of the reduced temperature difference between the coolant and the ambient air. In this study, indirect stack cooling system using $CO_2$ heat pump was designed and its stack cooling performance in releasing heat to the ambient was investigated. This work focuses on a series of processes that grasp the relation among the fuel cell power, the radiator capacity and the stack temperature. The purpose of this work is to find out a way to properly release sufficient amount of heat through the finite sized radiator, so that the stack power general ion can not be deteriorated due to the stack temperature increase. The optimization between the compressor power consumption and the fuel cel1 output power can be carried out to maximize the performance of fuel cell system.

• 신재생에너지
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• 제1권4호
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• pp.49-54
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• 2005

There is close relation between the heat generation in the fuel cell stack and the fuel performance. In PEM fuel cell vehicles, the stack coolant temperature is about $65^{\circ}C$, which is far lower than that for general automobile engine. Therefore, it is hard to release heat generated in the stack by using a radiator of limited size because of the reduced temperature difference between the coolant and the ambient air. In this study, indirect stack cooling system using $CO_2$ heat pump was designed and its stack cooling performance in releasing heat to the ambient was investigated. This work focuses on a series of processes that grasp the relation among the fuel cell power, the radiator capacity and the stack temperature. The purpose of this work is to find out a way to properly release sufficient amount of heat through the finite sized radiator, so that the slack power generation can not be deteriorated due to the stack temperature increase. The optimization between the compressor power consumption and the fuel cell output power can be carried out to maximize the performance of fuel cell system.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.199-203
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• 2002

In this paper, the effects of water contents on combustion characteristics of paper sludge and capacity of fluidized bed combustor(FBC) were investigated using 0.26m diameter, 1.75m height pilot-plant scale combustor. Combustion tests of paper sludge containing water contents between 40wt% and 50wt% were performed. The temperature and emission variation, the pressure inside combustor were measured to monitor the fluidization quality. The experimental results showed that 30kg/hr feeding rate of sludge containing water up to 45wt% was preferable for this system. Sludge loading rate, heat release rate were calculated from experimental data as major parameters showing FBC capacity. Comparsion with sludge loading rate from other source was also performed

• 폴리머
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• 제30권6호
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• pp.478-485
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• 2006

폴리(에틸렌글리콜)메틸에테르[poly (ethyleneglycol)nlethyl ether, MPEG] 곁사슬기와 짧고 강직한 디메틸페녹시(dimethylphenoxy) 곁사슬기를 갖는 폴리히드록시아미드(poly (hydroxyamide)s, PHAs)의 물성 및 난연특성을 DSC, TGA, FTIR, pyrolysis combustion flow calorimeter(PCFC), X-ray diffractometer를 사용하여 조사하였다. 중합체들의 최대분해온도는 공기 분위기하에서 $276{\sim}396^{\circ}C$의 범위를 보였다. PHAs의 heat release (HR) capacity와 total heat release (total HR) 값들은 MPEG의 분자량 증가에 따라 증가됨을 보였다. $290^{\circ}C$에서 열처리된 M-PHA 2의 경우 열처리 시간에 따라서 HR capacity 값들은 253 J/gK에서 42 J/gK로 감소하였고, 60% 중량 감소 온도는 $408^{\circ}C$에서 $856^{\circ}C$로 증가하였다. PHAs의 분해 활성화 에너지는 $129.3{\sim}235.1kJ/mol$의 범위를 보이고, 전환율에 따라 증가하였다. PHAs의 인장 모듈러스는 MPEG의 사슬길이가 증가함에 따라 감소하였으며, PBO로 전환된 후에는 초기 모듈러스보다 더 상승하였다.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.87-93
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• 2008

The $CO_2$ air conditioning system installed in fuel cell vehicles could be used either for stack cooling or for cabin cooling, and thus was used for the stack cooling when additional stack heat release was required over a fixed radiator capacity for high power generation. This study investigated the performance of the stack cooling system using $CO_2$ air conditioner at various operating conditions. Also, the heat releasing effectiveness and mutual interference were analyzed for the stack cooling system using an air conditioner and compared with the conventional radiator cooling system with/without cabin cooling. The heat release of the stack cooling system with the aid of $CO_2$ air conditioner increased up to 36% more than that of the conventional radiator cooling system with cabin cooling. Furthermore, the heat release of the stack cooling system using $CO_2$ air conditioner increased more by 7% than that of the conventional radiator cooling system without cabin cooling.

• Elastomers and Composites
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• 제56권2호
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• pp.72-78
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• 2021

A phase-change material (PCM) is a material that has the ability to delay heat transfer by absorbing heat from its environment or releasing heat to its environment while its phase changes from solid to liquid or liquid to solid at a specific temperature. As it is applied, it can contribute to environmental conservation such as energy savings and carbon dioxide emission reduction. In order for a PCM to store and release heat, the volume change during its phase transition should be large, and thus a phase transition space is required. When a PCM is used as a polymer additive, it is confined within the polymer, and there is no phase transition space; thus, its ability to absorb and release heat is significantly reduced. Therefore, in this study, porous silica was used to provide EVA/PCM compounds with sufficient space for their phase transition, and to improve the compatibility between the EVA and PCM, modified silica is used: surface-modified 5 wt% silica with 3-methacryloxypropyltrimethoxysilane. The compound was prepared and compared with the silica compound. The presence or absence of the modified silica surface modification was confirmed using Fourier-transform infrared spectroscopy and thermogravimetric analysis, the heat capacity of the compound was evaluated based on a differential scanning calorimetry analysis, and its mechanical strength and morphology were determined using scanning electron microscopy.

• Elastomers and Composites
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• 제42권3호
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• pp.177-185
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• 2007

유기화된 montmorillonite(O-MMT)와 인을 포함하는 polyamic acid(PPAA)를 용액 블렌딩하여 PAA/organoclay 나노 복합체를 제조하였다. 이들 나노 복합체들의 연구를 위하여 FT-IR, DSC, TGA, PCFC, SEM 그리고 XRD를 이용하였다. 나노복합체들의 제조확인은 FT-IR과 XRD 분석을 통하여 확인하였다. SEM 사진들은 O-MMT가 매트릭스 고분자에 비교적 고르게 분산되어 있음을 보여 주었고, XRD 결과를 통하여 O-MMT가 intercalation 되었음을 확인하였다. O-MMT/PPAA 나노복합체들의 열안정성 및 난연성은 순수한 PAA 보다 크게 높았으며, O-MMT/PPAA-0.2, 0.4, 0.6 복합체들의 열방출 용량과 총열방출 값들은 인의 함량 증가와 함께 감소하였다. 본 연구에서 제조된 나노복합체 필름들이 화재안전재료로서 사용될 수 있는 잠재성을 가지고 있음을 확인하였다.