• Journal of Biosystems Engineering
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• 제40권3호
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• pp.261-270
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• 2015

Purpose: Cold storage is the most popular method used to preserve highly perishable foods such as beef and fish. However, at refrigeration temperatures, the shelf life of these foods is limited, and spoilage leads to massive food waste. Moreover, freezing significantly affects the food's properties. Ice crystallization and growth during freezing can cause irreversible textural damage to foods through volumetric expansion, moisture migration induced by osmotic pressure gradients, and concentration of solutes,which can lead to protein denaturation. Methods: Although freezing can preserve perishable foods for months, these disruptive changes decrease the consumer's perception of the food's quality. Therefore, the development and testing of new and improved cold storage technologies is a worthwhile pursuit. Results: The process of maintaining a food product in an unfrozen state below its equilibrium freezing temperature is known as supercooling. As supercooling has been shown to offer a considerable improvement over refrigeration for extending a perishable product's shelf life, implementation of supercooling in households and commercial refrigeration units would help diminish food waste. Conclusions: A commercially viable supercooling unit for all perishable food items is currently being developed and fabricated. Buildup of this technology will provide a meaningful improvement in the cold storage of perishable foods, and will have a significant impact on the refrigeration market as a whole.

• 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.

• Journal of Animal Science and Technology
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• 제63권4호
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• pp.884-891
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• 2021

The study aimed to evaluate pork loin quality after short-term (ten-day) storage in a supercooling refrigerator. Pork loin samples were stored for 10 days in a traditional refrigerator (control) and a commercially available supercooling refrigerator (SC). Pork quality measurements included meat pH, meat color, water holding capacity (drip loss and cooking loss), tenderness (hardness), and a sensory evaluation. Temperature changes of 0.45 ± 0.2℃ and 0.02 ± 0.25℃ occurred in the control and the SC, respectively, during 10 days of storage. The temperature in the SC chamber did not remain below freezing point, failing to meet expectations. Regarding the pork quality measurements, only the drip losses in the control and the SC were significantly different (4.45% vs. 2.59%, p < 0.01) after 10 days of storage. There were no significant differences between the two types of refrigerator in terms of the other measurements. Additionally, the overall acceptability of the pork loin did not vary significantly between the control and the SC when the sensory evaluation was performed. Therefore, a commercial SC could prove beneficial in terms of water holding capacity during the short-term storage of meat. Further research should be performed to evaluate quality changes that occur during long-term storage of meat in SC s and evaluate a wide range of meat, such as beef and chicken.

• Journal of Advanced Marine Engineering and Technology
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• 제21권5호
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• pp.527-534
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• 1997

Freezing of an aqueous sodium cWoride solution (Nacl- H20) saturating a packed bed with ini¬tial salt concentrations of 5, 10, 15(k by weight is investigated experimentally in a rectangular cav¬ity. The system was cooled from the top, bottom and a vertical side wall. For the freezing experi¬ments from below, there was little effect of the initial salt concentration throughout the freezing process, and the global freezing rate was not affected by the initial salt concentration. For the freezing from above, the size of the mush region decreased and the mushlliquid interface became flatter as the initial liquid concentration is decreased. For the freezing from vertical side wall, reheating of the mixture was intensified with an increase in the initial salt concentration. For Ci= 5%, supercooling was observed only at the early times of freezing process, but for Ci= 15% small supercooling was observed throughout the freezing process.

• 설비공학논문집
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• 제16권12호
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• pp.1212-1217
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• 2004

This study investigated the improvement effect of a small portion of surfactant on the supercooling and the phase change temperature of TMA 30 wt% clathrate compound when surfactant is added to the clathrate compound. The experiments are carried out under various conditions; the concentration of additive ranges between 0.08～0.12 wt% and the temperature of heat source ranges between -8 and -6$^{\circ}C$. The experimental results show that the phase change temperature with the surfactant of 0.1 wt% is lower by 1$^{\circ}C$ than TMA 30 wt% and the supercooling is reduced by 1$0^{\circ}C$.

• 설비공학논문집
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• 제16권3호
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• pp.258-264
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• 2004

The ice thermal storage system is to use consolation latent heat of water. But, supercooling phenomenon of water during phase change is to increase the cooling capacity and to decrease COP of the refrigerator. Furthermore, this causes the operation cost of system to increase and the efficiency of energy to decrease. Therefore, the better thermal storage material than the water is required. The purpose of this study is to improve supercooling characteristics and thermal properties of TMA 30wt% clathrate by using Ethanol.

• 산업식품공학
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• 제22권4호
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• pp.321-327
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• 2018

19종의 과채류에 대한 동결점 및 빙핵 형성 온도, 함수율, 경도, 당도, pH를 측정하여 Pearson 상관분석을 하였다. 동결점은 함수율과 당도에 p<0.01의 유의적인 상관관계를 나타냈으나, 빙핵 형성 온도는 당도에만 p<0.05의 상관관계를 보였다. 특히 동결점과 빙핵 형성 온도의 차이값인 과냉각 격차 FSD와는 함수율과 당도 등이 모두 상관관계를 보이지 않았다. 호기성세균, 유산균, 효모, 곰팡이의 다양한 미생물이 분포하는 배추에 대한 미생물 분석과 FSD와의 상관분석을 수행하였는데, 호기성 세균과 p<0.01의 상관관계가 나타났다. 호기성 세균을 9.4 log CFU/mL의 농도로 접종한 식염수와 이를 멸균한 시료를 각각 $10^2$, $10^4$, $10^6$ 배로 희석하여 동결점과 빙핵 형성 온도 분석에서도 높은 농도의 호기성 세균이 빙핵 형성 온도를 높이는 결과가 나왔다. 하지만, 약 5 log CFU/mL 수준 이하에서는 멸균식염수와 빙핵 형성 온도의 통계적 차이가 없는 것으로 나타났다.

• 에너지공학
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• 제14권1호
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• pp.18-23
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• 2005

본 연구는 저온축열물질로서 TMA(Tri-methyl-amine, (CH₃)₃N)를 20～25 wt％로 포함하고 있는 TMA-물계 포접화합물의 냉각특성에 대하여 냉열원온도 -5℃에서 실험적으로 연구를 수행하였다. 연구결과, TMA의 질량농도가 증가할수록 상변화온도와 비열이 증가하였으며, 과냉도가 감소하고 액상유지시간이 단축되었다 특히, TMA 25wt%를 포함한 TMA-물계 포접화합물은 상변화온도 평균 5.8℃, 과냉도 8.0℃, 액상유지시간 10분, 비열 4.099kJ/kg℃를 나타내었다. 본 연구의 결과로부터 TMA-물계 포접화합물은 물보다 높은 상변화온도를 나타내었으며, 과냉도가 감소하고, 액상유지시간이 단축되는 과냉각 억제효과를 확인 할 수 있었다.

• 태양에너지
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• 제10권2호
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• pp.28-37
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• 1990

빙축열의 문제점인 물의 과냉각을 억제 또는 제거하기 위하여 고흡수성 고분자를 조핵제로 사용하는 방법이 고안되었다. 축열재인 물을 $25^{\circ}C$에서 $-12^{\circ}C$로 냉각시킨 결과 순수한 물의 경우 샘플중 25%의 샘플은 전혀 결빙되지 않았으며 나머지 얼음이 생성된 샘플의 경우도 평균 $9.8^{\circ}C$의 과냉각을 보인 반면, 조핵제가 첨가된 경우 35%가 전혀 과냉각을 보이지 않았으며 과냉각이 일어난 샘플의 평균과 냉각온도 역시 현저히 감소되었다. 0.5wt%의 고흡수성 고분자가 첨가된 축열재를 사용하여 캡슐타입으로 제작한 축열조에서 열전달 실험을 실시한 결과 과냉각은 전혀 관찰되지 않았으며 이로 인하여 순수물을 축열재로 사용하는 경우보다 축열속도가 증가하였다. 이상의 결과로부터 고흡수성 고분자가 빙축열 시스템의 조핵제로 사용될 수 있음을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1080-1083
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• 2017

한국형발사체의 설계안에는 산화제 배관의 geysering 현상과 펌프 입구의 cavitation 현상을 방지하기 위하여 발사대기 중 산화제인 액체산소를 과냉각 하여 공급하는 시나리오가 포함되어 있다. 이 조건을 75톤급 엔진 개발 시험 단계에서 검증하기 위해 엔진 연소시험설비에는 액체산소를 과냉각 할 수 있는 시스템이 적용되었다. 여기에는 진공 이젝터를 이용한 방법과 탱크 내 헬륨 분사를 통한 방법이 적용되었으며, 성능 평가를 위해 각각에 대한 과냉각 시험이 수행되었다. 두 시험에서 모두 약 17분간 시험이 진행되었으며, 탱크 50%수위 지점 기준 이젝터를 이용한 시험에서는 약 3.3K, 헬륨 분사를 이용한 시 험에서는 약 2.2K 의 과냉각 결과를 나타내었다.