• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1746-1750
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• 2004

The objective of this study is to investigate the effect of supercooling repression on the clathrate compound by adding additives. For this purpose, phase change temperature and supercooling were measured when additives added to TMA30wt% clathrate for heat source temperature of $-6^{\circ}C$. The experimental results show that the phase change temperature with the chloroform of 0.1wt% is higher by $0.3^{\circ}C$ than TMA30wt% and the supercooling with the surfactant 0.1wt% is reduced by $9.2^{\circ}C$.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1165-1170
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• 2004

The purpose of this study is to investigate the supercooling improvement of TMA30wt% clathrate when the chloroform is added to it. For this purpose, phase change temperature and supercooling are measured and evaluated experimentally in heat source of $-7^{/circ}C$. The results show that phase change temperature and supercooling are improved. From the results, this research can provide and important data for the low temperature thermal storage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.173-178
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• 2010

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity are increased and COP are decreased due to supercooling of water in the course of phase change from liquid to solid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N$) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature are increased and the supercooling degree and the specific heat are decreased according to the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of $5.8^{\circ}C$ and the supercooling degree of $8.0^{\circ}C$, retention time of liquid phase for 651sec and specific heat of 3.499 kJ/kgK in the cooling process. This expressed good than different concentration of TMA cooling characteristic. Like this, to apply TMA 25wt%-water clathrate compound is determined by advantageous as the low temperature latent heat storage material.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.79-79
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• 2004

• Journal of Energy Engineering
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• v.14 no.1
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• pp.18-23
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• 2005

This study is investigated the cooling characteristics of the TMA clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20～25 wt％ as a low temperature storage material at -5℃ heat source. The results showed that as the concentration of TMA is increased, phase change temperature and specific heat are increased, but the supercooling and retention time of liquid phase are decreased. Especially, low temperature storage material containing TMA 25 wt％ has the average of phase change temperature of 5.8℃, supercooling of 8.0℃, retention time of liquid phase for 10 minutes and specific heat of 4.099 kJ/kg℃ in the cooling process. From the results of this study, TMA clathrate compound showed higher phase change temperature than water md supercooling repression effect.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.216-224
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• 1997

In the recent 10 years the protected cultivation area in Korea has been increased rapidly, and now it is very important issue to develop the heating and cooling system using the renewable energy, because the greenhouse heating and cooling cost is increased with the fossil fuel price rises. Actually the development of the cooling system is more difficult than that of the heating system, since the cooling load of greenhouse in the summer season is 2―3 times larger than the heating load in the winter season. In this study low temperature phase change materials (LTPCM) for the cold storage system were selected and developed. The theoretical and experimental analysis of thermal characteristics of LTPCM makes it possible to control the phase change temperature and stabilize the thermo-physical properties. LTPCM developed in this study has good advantages to be used as the cold storage not only for the house and working space in factory but also for the cold storage of agricultural and live-stock products.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.115-122
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• 1996

Heat transfer characteristics of low temperature latent heat storage systems have been examined for the circular finned and unfinned tubes using Na$_2$B$_4$O$\_$7/10H$_2$O as a phase change material. In order to reduce the supercooling of PCM, 3 wt% of Na$_2$B$_4$O$\_$7/10H$_2$O was added as the nucleating agent and 2.2 wt% of acrylic acid sodium sulfate was used as the thickener. The heat storage vessel has dimension of 530 mm height, 74 mm 1.D. and inner heat transfer tube is 480 mm height and 13.5 mm O.D. Water was employed as the heat transfer fluid. During the heat recovery experiment, the heat recovery rate was affected by the flow rates and inlet temperature of heat transfer fluid. The enhancement of heat transfer by fins over the unfinned tube system was found to be negligible in the thin finned tube systems, whereas the heat transfer coefficient in the thick finned tube system is approximately 60% higher than that in the unfinned lobe system. The experimentally determined heat transfer coefficient for the unfinned tube and thick finned tube systems are 150-260 W/㎡$^{\circ}C$ and 230-530 W/㎡$^{\circ}C$, respectively. The fin efficiency based on the heat transfer coefficient and area increased by fins was found to be 0.05 and 0.26 for the thin and the thick finned tube systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.2
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• pp.72-78
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• 2014

In a cold chain, the refrigerator is also employed for defrosting, by using an electric heater, which consumes 15% of the power for the system operation. In this study, the condensation heat of the refrigerant was suggested as the heat source of defrosting heat, instead of that from an electric defrost heater. The heat for defrosting was stored to a phase change material (PCM, NMP : $52^{\circ}C$) in thermal storage, and was periodically supplied to the evaporator by a circulation loop of brine. As a result, a defrost time by the PCM was obtained that was less than or equal to that by the electric heater. Moreover, power consumption during defrosting was saved by up to 99% of that of the electric heater.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.5
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• pp.555-566
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• 2023

In this study, a composite phase change material (CPCM) produced using the SOL-GEL technique was developed as a thermal energy storage medium for low-temperature applications. Tetradecane and activated carbon (AC) were used as the core and supporting materials, respectively. The tetradecane phase change material (PCM) was impregnated into the porous structure of AC using the vacuum impregnation method, and a thin layer of silica gel was coated on the prepared composite using the SOL-GEL process, where tetraethyl orthosilicate (TEOS) was used as the silica source. The thermal performance of the CPCM was analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC results showed that the pure tetradecane PCM had melting and freezing temperatures of 6.4℃ and 1.3℃ and corresponding enthalpies 226 J/g and 223.8 J/g, respectively. The CPCM exhibited enthalpy of 32.98 J/g and 27.7 J/g during the melting and freezing processes at 7.1℃ and 2.4℃, respectively. TGA test results revealed that the AC is thermally stable up to 500℃, which is much higher than the decomposition temperature of the pure tetradecane, which is around 120℃. Moreover, in the case of AC-PCM and CPCM thermal degradation started at 80℃ and 100℃, respectively. The chemical stability of the CPCM was studied using Fourier-transform infrared (FT-IR) spectroscopy, and the results confirmed that the developed composite is chemically stable. Finally, the surface morphology of the AC and CPCM was analysed using scanning electron microscopy (SEM), which confirmed the presence of a thin layer of silica gel on the AC surface after the SOL-GEL process.