• 한국축산식품학회지
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• 제36권5호
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• pp.650-655
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• 2016

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat.

• Journal of Ginseng Research
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• 제20권2호
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• pp.179-183
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• 1996

One exotherm was detected in the intact ginseng seeds containing more than 35% water, but in seeds with 20% there was no exotherm. The shapes of exotherm were remarkably uniform without relation to water content above 35%. The temperature at the initiation of freezing varied from -3.5$^{\circ}C$ to -9.6$^{\circ}C$ with the different water content in the seeds, and the Initial temperature of freezing delayed with the decrease of water content. The resistance damage at low temperature appeared in order of maln body, rhizome, lateral root of 3-year-old yearling rhizome, and fine root of 3-year-old. Ginseng roots didn't receive any damage at -5$^{\circ}C$ for 24 hours. Otherwise they received serious damage below -1$0^{\circ}C$ even for 5 hours'exposure. Hence, alternative low temperature gave more severe damage compared to constant low temperature. This result suggests that the Possibility of receiving injury at low temperature was higher during the thawing season of the early spring than in the winter.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.213-216
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• 2005

Salt attack and freezing & thawing test, one of the combined deterioration tests was performed to explore the mechanism of concrete structure deterioration under marine environment. Simple submerging test was proceeded to draw out its diffusion factor with salt water at the same time. Some of the mechanisms were driven with using three types of cements and four kinds of salt water concentrations. $\circ$ TBC was more durable than OPC or SRC for freezing and thawing action $\circ$ The higher chloride concentration of salt water was, the faster relative dynamic elastic modulus decreased and the higher the loss of weight was. $\circ$ The diffusion factor of TBC was smaller than those of TBC or SRC at simple submergence of concrete specimens into salt water.

• 한국축산식품학회지
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• 제34권6호
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• pp.777-783
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• 2014

This study investigated the effect of various freezing and thawing techniques on the quality of beef. Meat samples were frozen using natural convection freezing (NF), individual quick freezing (IQF), or cryogenic freezing (CF) techniques, followed by natural convection thawing (NCT) or running water thawing (RT). The meat was frozen until the core temperature reached $-12^{\circ}C$ and then stored at $-24^{\circ}C$, followed by thawing until the temperature reached $5^{\circ}C$. Quality parameters, such as the pH, water binding properties, CIE color, shear force, and microstructure of the beef were elucidated. Although the freezing and thawing combinations did not cause remarkable changes in the quality parameters, rapid freezing, in the order of CF, IQF, and NF, was found to minimize the quality deterioration. In the case of thawing methods, NCT was better than RT and the meat quality was influence on the thawing temperature rather than the thawing rate. Although the microstructure of the frozen beef exhibited an excessive loss of integrity after the freezing and thawing, it did not cause any remarkable change in the beef quality. Taken together, these results demonstrate that CF and NCT form the best combination for beef processing; however, IQF and NCT may have practical applications in the frozen food industry.

• 한국태양에너지학회 논문집
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• 제32권6호
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• pp.127-133
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• 2012

This paper is an experimental study on the freezing protection valve used for solar water heating, air-conditioning systems, and plumbing systems. When the phase change occurs from liquid to solid, most of the substances except water volumetrically shrink. And referred to as PCM(Phase Change Material) a substance with such properties, the phase change temperature varies depending on the material. To prevent the freezing of the plumbing system, such as air-conditioning system in the winter season, we developed a several types of freezing protection valve using PCM whose freezing temperature are $2-4^{\circ}C$. The working principle of the freezing protection valve is that the fluid inside the pipe is released to prevent the system-collapse when fluid temperature reaches the freezing temperature of the PCM. And then the valve is closed and returned to the original position automatically when the temperature of the operating fluid rises. In this paper, the operating temperatures, discharge flow rate and the response characteristics of the valve during the operation are tested and investigated. From the results of this research the freezing protection valves employing PCM are expected to be commercialized in the near future.

• Geomechanics and Engineering
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• 제18권2호
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• pp.189-203
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• 2019

Brine leakage is a common phenomenon during construction facilitated by artificial freezing technique, threatening the stability of frozen wall due to the continual thawing of already frozen domain. This paper takes the frequently encountered soft clay in Wujiang District as the study object, and remolded specimens were prepared by mixing calcium chloride solutions at five levels of concentration. Both the deformation and pore water pressure of frozen specimens during thawing were investigated by two-stage loading tests. Three sections were noted from the changes in the strain rate of specimens during thawing at the first-stage load, i.e., instantaneous, attenuated, and quasi-stable sections. During the second-stage loading, the deformation of post-thawed soils is closely correlated with the dissipation of pore water pressure. Two characteristic indexes were obtained including thaw-settlement coefficient and critical water content. The critical water content increases positively with salt content. The higher water content of soil leads to a larger thaw-settlement coefficient, especially at higher salt contents, based on which an empirical equation was proposed and verified. The normalized pore water pressure during thawing was found to dissipate slower at higher salt contents, with a longer duration to stabilize. Three physical indexes were experimentally determined such as freezing point, heat conductivity and water permeability. The freezing point decreases at higher salt contents, especially as more water is involved, like the changes in heat conductivity. The water permeability maintains within the same order at the considered range of salt contents, like the development of the coefficient of consolidation. The variation of the pore volume distribution also accounts for this.

• 한국식품영양과학회지
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• 제21권2호
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• pp.213-218
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• 1992

식품의 동결중에 생성되는 빙결정의 크기에 미치는 동결조건의 영향을 조사하고 그 관계를 정량적으로 평가함과 아울러 동결조건과 빙결정 분산구조와의 관계를 이론해석에 의해 조사한 결과, 1. 동결이동속도 u는 생성빙결정의 평균경 d$_{p}$와 u .d$_{p}$/D~constant의 관계에 있음을 간단한 차원해석에 의해 예측이 가능하였다. 2. 2% 한천 겔, 5%한천 겔, 20% 젤라틴 겔, 돈육의 순서로 동결점에 도달하는 시간이 빨라지며 동결시간 및 최대빙결품 생성대의 통과시간은 냉매온도와 선형적인 관계를 나타내었다. 3. 대두 단백질 겔중에 생성되는 빙결정의 평균경 d$_{p}$와 동결계면 이동속도 u 는 반비례 관계를 나타내었으며, 이로부터 구해진 u .d$_{p}$의 값은 3.4$\times$$10^{-6}$ $\textrm{cm}^2$/sec로 예측 이론식이 유효한 것으로 사료되었다. 4. 동결보존중의 대두 단백질 겔 내부에 생성된 빙결정의 성장에 미치는 보존온도의 영향을 조사한 결과, 양자가 빙결정의 성장에 미치는 영향은 거의 없는 것으로 나타났다. 5. 동결조건과 동결계면구조와의 사이에 Moving velocity of freezing front= (Mass transfer rate of water at freezing front)$\times$ (Surface area of freezing front) 의 관계를 나타내었다.

• 설비공학논문집
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• 제3권5호
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• pp.386-394
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• 1991

Freezing of saturated porous media contained in a rectangular cavity has been studied experimentally. Water and different diameter glass beads consitituted the liquid and porous media. Solidification front shape, the effects of bead diameter and initial liquid temperature was investigated. When the hot wall temperature was below $4^{\circ}C$, the freezing rate was higher at the top than at the bottom due to the density inversion, but with increasing the hot wall temperature the freezing rate at the top was effected by the liquid temperature and was lower than at the bottom. With increasing the bead diameter, the difference of freezing rate between top and bottom was increased and depends on thermal conductivity. When the liquid temperature was low in the beginning, the freezing rate was high, but with increasing the time almost the same with those of high temperature liquid.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.264-270
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• 2002

The frost heaving pressure can be a problem for weakening of the railroadbed material. In this study, upon freezing a saturated soil in a closed-system from the top, a considerable pressure was developed. This pressure is induced as a result of a curved ice-water interface. This study was initiated to investigate the soils frost heaving expansion pressure and physical characteristics resulting from freezing and freezing-thawing cycle process. Weathered granite soils, sandy soil were used in the laboratory freezing test subjected to thermal gradients under closed-systems.

• 상하수도학회지
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• 제22권5호
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• pp.561-569
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• 2008

We analyzed contents of cations and anions for the domestic bottled drinking water. Results showed that total cation content was 45.81 mg/L and contained 40% of Ca. The content of cations were decreased in the order of Ca>Si>Na>Mg>K. Total anion content was 12.20 mg/L and contained 90% of ${SO_4}^{2-}$ and $Cl^-$. $F^-$ and $NO_{3-}N$ were a little contained. While Si content was reduced 2.3~75.7%(mean value:38.5%) after freezing, Ca content was reduced 45.2% after boiling. It showed that water containing higher Ca content was significantly decreased after boiling. Precipitates formed by freezing and boiling is composed of minerals such as Si and Ca. Compared to minerals from food intake, concentrations of minerals from water intake are expected to be less influenced. It is recommended Bottled Water that contains more than 20 mg/L of Ca(exceeding water-quality standard for turbidity) is safe to drink without thawing and boiling.