• Journal of Biosystems Engineering
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• v.27 no.1
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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%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4749-4755
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• 2014

In this study, to maximize the heat release from the heat generating environment, such as a high-capacity inverter, the heat release performance of the extruded-type heat sinks with the variation of the base thickness were investigated using the experimental and numerical methods. The base thickness was varied from 5 to 14 mm. The heat release was characterized by the amount of heat released through the heat sink, the surface temperature of heat sink base between the heat sources, and temperature of heat sources. The surface temperatures between heat sources and the amounts of heat release were improved more as the base thickness was decreased. In contrast, the temperatures of the heat sources decreased with increasing base thickness. Based on the case study of these heat sinks, it is believed that a heat sink with a 9.5mm-thick base was optimized for the heat release.

• Journal of Adhesion and Interface
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• v.14 no.3
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• pp.135-145
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• 2013

Epoxy resin compositions were studied on the view of self-extinguishing properties without retardant additives and suitability as materials of eco-friendly EMC (Epoxy molding compound). Cured epoxy and phenolic resin composition having conjugated double bond of aromatic structure exhibited self-extinguishing properties and low heat release capacity. In this study, the structure of long conjugated double bond of hetero-atom type azomethyne group between conjugated double bonds of aromatic structure showed lower heat release capacity. Low heat release capacity seemed to be related with high reaction enthalpy, $T_g$ and reactivity affected by hetero-atom structure in azomethyne group.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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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.

• New & Renewable Energy
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• v.1 no.4 s.4
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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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• 2002.06a
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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

• Polymer(Korea)
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• v.30 no.6
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• pp.478-485
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• 2006

Physical properties and flammability of polyhydroxyamides (PHAs) haying poly (ethylene-glycol) methyl ether (MPEG) and/or dimethylphenoxy pendants were studied by using DSC, TGA, FTIR, pyrolysis combustion flow calorimeter (PCFC), and X-ray diffractometer. The degradation temperatures of the polymers were recorded in the ranges of $276{\sim}396^{\circ}C$ in air. PCFC results showed that the heat release (HR) capacity and total heat release (total HR) values of the PHAs were increased with in-creasing molecular weight of MPEG. In case of M-PHA 2 annealed at $290^{\circ}C$, the values of HR capacity were siginificantly decreased from 253 to 42 J/gK, and 60% weight loss temperatures increased from 408 to $856^{\circ}C$ with an annealing temperature. The activation energy for the decomposition reaction of the PHAs showed in the range of $129.3{\sim}235.1kJ/mol$, which increased with increasing conversion. Tensile modulus of PHAs were decreased as increasing chain of MPEG, and showed an increase more than initial modulus after converted to PBOs.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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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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• v.56 no.2
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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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• v.42 no.3
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• pp.177-185
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• 2007

Polyamic acid(PAA)/organoclay nanocomposites containing phosphorous were prepared by solution blending of phosphorylated PAA(PPAA) and organically modified montmorillonite(O-MMT) as a type of layered clays. The nanocomposites were characterized by FT-IR, DSC, TGA, PCFC, SEM, and XRD. The preparation of nanocomposites was confirmed by FT-IR and XRD. SEM pictures showed that the organoclay was dispersed well in the PAA matrix relatively. XRD results indicated that the O-MMT layers were intercalated. The thermal stability and flame retardancy of O-MMT/PPAA nanocomposites were higher than those of pure PAA. PCFC results also showed that the heat release capacity and total heat release values of O-MMT 4 wt%/PPAA-0.2, 0.4, 0.6 composites were decreased with increasing the mole ratio of phosphorous. It was found that the nanocomposite films had the potential to be used as a fire safe material.