• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2471-2475
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• 2007

Clathrate compound is the material that host in hydrogen bond forms cage and guest is included into it and combined. Crystallization of hydrate is generated at higher temperature than that of ice from pure water. And physical properties according to temperature are stable and congruent melting phenomenon is occurred without phase separation. But clathrate compound still had supercooling problem occurred in the course of phase change and supercooling should be minimized because it affects efficiency of equipment very much. Therefore, various studies on additives to restrain this or heat storage methods are needed. In this study was investigated the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N)$ of 20${\sim}$25 wt% as a low temperature latent heat storage material. And ethanol$(CH_3CH_2OH)$ was added and its cooling characteristics were studied experimentally to restrain supercooling of TMA-water clathrate compound.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.296-301
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• 2009

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N)$ of $20{\sim}25wt%$ as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of $5.8^{\circ}C$, the supercooling degree of $8.0^{\circ}C$ and the specific heat of 3.499 kJ/kgK in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

• 한국초전도ㆍ저온공학회논문지
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• 제26권1호
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• pp.20-24
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• 2024

Over the past four years, as the COVID-19 pandemic has struck the world, cold chain of COVID-19 vaccination has become a hot topic. In order to overcome the pandemic situation, it is necessary to establish a cold chain that maintains a low-temperature environment below approximately 203K (-70℃), which is the appropriate storage temperature for vaccines, from vaccine suppliers to local hospitals. Usually, cryocoolers are used to maintain low temperatures, but it is difficult for small-scale local distribution to have cryocooler due to budget and power supply issues. Accordingly, in this paper, a cryogenic TSU (Thermal storage unit) system for vaccination cold chain is designed that can maintain low temperatures below -70℃C for a long time without using a cryocooler. The performance of the TSU system according to the energy storage material for using as TSU is experimentally evaluated. In the experiments, four types of cold storage materials were used: 20% DMSO aqueous solution, 30% DMSO aqueous solution, paraffin wax, and tofu. Prior to the experiment, the specific heat of the cold storage materials at low temperature were measured. Through this, the thermal diffusivity of the materials was calculated, and paraffin wax had the lowest value. As a result of the TSU system's low-temperature maintenance test, paraffin wax showed the best low-temperature maintenance performance. And it recorded a low-temperature maintenance time that was about 24% longer than other materials. As a result of analyzing the temperature trend by location within the TSU system, it was observed that heat intrusion from the outside was not well transmitted to the low temperature area due to the low thermal conductivity of paraffin wax. Therefore, in the TSU system for vaccine storage, it was experimentally verified that the lower the thermal diffusivity of the cold storage material, the better low temperature maintenance performance.

• 한국해양공학회지
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• 제14권1호
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• pp.23-28
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• 2000

The fatigue crack growth behavior of the cold-rolled STS 304 steel developed for membrane material of LNG storage tank was examined experimentally at 293K, 153K and 111K. The fatigue crack growth rate(do/dN) tends to increase as the stress ratio (R) increases over the testing temperature when compared at the same stress intensity factor range($\Delta$K). The effect of R on do/dN is more explicit at low temperatures than at room temperature. The resistance of fatigue crack growth at low temperatures is higher compared with that at room temperature which is attributed to the extent of strain-induced martensitic transformation at the crack tip. The temperature dependence of fatigue crack growth resistance is gradually vanished with an increase in $\Delta$K which correlates with a decreasing fracture toughness with decreasing temperature. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperature are mainly explained by the crack closure and the strengthening due to the martensitic transformation.

• 태양에너지
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• 제7권1호
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• pp.61-74
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• 1987

This review evaluates the state of art in the field of high-temperature energy storage materials and systems. The physical and chemical properties, corrosion data and practical applications of the phase change materials, especially the inorganic salts applicable to storage temperature in the range of $100-850^{\circ}C$ have been summarized. Fluoride salts have excellent thermal storage properties, but these are less attractive in terms of cost and corrosion problem of container materials. The nitrate and nitrite have attractive properties in the temperature range up to $600^{\circ}C$, at which the rate of decomposition becomes unacceptable. Carbonates euteutic salts can be considered as the most promising energy storage material on the basis of their low cost and excellent material compatibility for corrosion in the temperature range up to $850^{\circ}C$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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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.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권1호
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• pp.32-36
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• 2009

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N$) of $20{\sim}25wt%$ as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25 wt% has the average phase change tempera ture of $5.8^{\circ}C$, the supercooling degree of $8.0^{\circ}C$ and the specific heat of 3.499 kJ/kgK in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1663-1666
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• 2003

TMA clathrate that is used by PCM of ice storage system in this research creates hydrate crystallization at higher temperature than pure water, and application is expected as PCM because having comparative big dormant temperature without phase separation phenomenon. In case this research uses TMA clathrate by PCM, choose admixture by purpose to control or remove subcooling of TMA clathrate and evaluated experimentally. Subcooling is improved and can expect contraction of freezing machine running time and increase of coefficient of performance as that add admixture to TMA clathrate conclusively. Also, may supply thermal storage system that apply low temperature potential heat thermal storage material that subcooling is improved more extensively laying stress on medium size building and small size building, can expect allowance through localization of ice storage system.

• 대한기계학회논문집B
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• 제34권2호
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• pp.173-178
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• 2010

빙축열시스템은 저온잠열저장을 위해 물을 사용한다. 그러나 물은 액체에서 고체로 상변화를 하는 과정에서 물의 과냉각 현상에 의하여 냉동기의 냉동용량 증가와 COP감소의 원인이 되고 있다. 본 연구는 저온잠열축열물질로 적용 가능한 TMA(Tri-methyl-amine, $(CH_3)_3N$) 20~25 wt%를 포함하고 있는 TMA-물계 포접화합물(TMA-water clathrate compound)의 냉각특성에 대한 실험적 연구를 수행하였다. 실험적 연구 결과, TMA 질량농도가 높을수록 상변화온도는 증가하였고, 과냉각도와 비열은 감소하였다. 특히, TMA 25wt%를 포함하고 있는 포접화합물은 냉각과정동안 평균 상변화온도 $5.8^{\circ}C$와 과냉각도 $8.0^{\circ}C$, 액상유지시간 651sec 및 비열 3.499 kJ/kgK로서 다른 TMA 농도보다 양호한 냉각특성을 나타내었다. 이와 같이 저온잠열축열물질로서 TMA 25wt%-물계 포접화합물을 적용하는 것이 유리할 것으로 판단된다.

• 생물환경조절학회지
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• 제17권2호
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• pp.96-100
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• 2008

꼬투리째 먹는 채소인 풋꼬투리 강낭콩의 수확후 포장 및 저장 유통온도별 품질보존 및 상품성에 미치는 영향을 조사하였다. 저장중 중량의 변화에서 PP필름 포장시는 변화가 없었으나 골판지박스 포장시는 저장 온도가 높고, 저장기간이 길어질수록 중량 감소율이 현저하였다. 저장중 경도는 저온저장이 상온저장보다 높게 유지되었다. 비타민 C함량은 저장중 모든 처리에서 감소되었고, 그 감소의 폭은 상온저장보다는 저온저장 시 적었다. 엽록소함량은 비닐필름 포장시는 저장온도간에 차이가 없었으나, 박스포장시는 상온저장시 엽록소함량의 감소가 저온저장보다 컸다. 외관 상품성을 표시하는 신선도는 비닐포장이나 골판지박스에 속비닐 넣은 후 산물을 포장하여 $8{\sim}10^{\circ}C$정도에서 저장 유통시는 상품유지기간이 8일 정도로 상온보관대비 4일정도 연장되었다.