• 대한조선학회논문집
• /
• 제50권3호
• /
• pp.167-174
• /
• 2013

Model ice forming process in ice tank needs several steps of seeding, freezing, tempering. In those process, one of the most important factors to affect the accuracy of experiment is the homogeneity of the ice thickness and the temperature. This paper investigated a computational and statistical method to assess the uniformity of the model ice. In addition, the different configurations of freezing systems were considered to improve the uniformity. Qualitative assessment using streamlines from the cooling units was carried out by computational fluid dynamics (CFD) and the quantitative evaluations of the homogeneity were compared using the temperature distribution on the ice surface. In addition, multi species transport analysis is introduced to understand the circulation efficiency of cold air from the cooling units. As the results, optimized configurations were determined by adjusting the angles of vane in the cooling units.

• 한국결정학회지
• /
• 제13권3_4호
• /
• pp.172-176
• /
• 2002

Pb(Mg /sub 1/3/Nb/sub 2/3/)O₃-PbTiO₃ 계 완화형 강유전체에서 PbTiO₃ 첨가량 변화 및 온도 변화에 따른 상전이 거동을 초전특성 및 유전완화현상 고찰을 통해 고찰하였다. -40∼200℃의 상전이 온도범위에 걸쳐 초전 및 유전특성을 살펴보았으며 특히 Vogel-Fulcher 관계식에 의한 freezing temperature를 도출하였다. 이러한 모든 실험적 결과들로부터 기존에 제안되었던 Pb(Mg /sub 1/3/Nb/sub 2/3/)O₃-PbTiO₃ 고용체 시스템에 대한 상평형도를 다소 수정하여 제안하였다.

• 설비공학논문집
• /
• 제19권9호
• /
• pp.647-653
• /
• 2007

In dynamic ice storage system(DISS), ice slurry is formed not only from solution freezing by mechanical removing parts but also supercooled solution. However, in order to perform continuous ice formation in the system without mechanical moving parts, supercooled aqueous solution should be formed stable through cooling heat exchanger and be dissolved uniformly in storage tank. In previous study, the time of ice slurry increased as the pressure of the cooling heat exchanger(PHX) increased. In this study, a cooling experiment of an ethylene glycol 7mass% solution was performed with various inlet temperature of the PHX, which has constant brine inlet temperature of $-7^{\circ}C$. The temperature in the storage tank maintained to freezing point of the solution. At results, the time of ice slurry formation increased as the supercooling degree decreased and the cooling rate increased.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
• /
• pp.83-85
• /
• 2011

This study investigated the results of insulation heat curing method using double layer bubble sheet in concrete in cold weather environment. First of all, when double bubble sheets are applied, it was shown that concrete was protected from early freezing by remaining between 7℃ and 3℃ even in case outside temperature drops -7℃ below zero until the 3d day from piling. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

• 조명전기설비학회논문지
• /
• 제22권9호
• /
• pp.69-74
• /
• 2008

동절기 전차선의 서리와 결빙은 매우 심각한 문제를 발생시킬 수 있다. 팬터그래프의 집진 스트립의 기계적 표면과 전차선 사이에 서리 또는 결빙으로 인한 아크가 발생하게 된다. 이에 따른 전기적 저항은 팬터그래프와 전차선 사이의 전류의 풀질을 감소시킨다. 해빙시스템은 통절기 전차선의 서리와 결빙을 녹이는 역할을 한다. 해빙시스템의 원리는 전차선의 임피던스의 Joule열을 이용하여 서리와 결빙을 제거하는 것이므로 전차선의 온도는 인가전류가 증가할수록 증가하였으며, 풍속이 증가할수록 감소하는 것을 알 수 있었다.

• 한국초전도ㆍ저온공학회논문지
• /
• 제22권4호
• /
• pp.45-50
• /
• 2020

In this research, the variation of round-trip efficiency in a liquid air energy storage system (LAES) is calculated and an optimal configuration is found. The multiple stages of cold energy storage are simulated with several materials that process latent heat at different temperature ranges. The effectiveness in the charging and discharging processes of LAES is newly defined, and its relationship with the round-trip efficiency is examined. According to defined correlation, the effectiveness of the discharging process significantly affects the overall system performance. The round-trip efficiency is calculated for the combined cold energy storage materials of aqueous dimethyl sulfoxide (DMSO) solution, ethanol, and pentane theoretically. The performance of LAES varies depending on the freezing point of the cold storage materials. In particular, when the LAES uses several cold storage materials, those materials whose freezing points are close to room temperature and liquid air temperature should be included in the cold storage materials. In this paper, it is assumed that only latent heat is used for cold energy storage, but for more realistic analyzes, the additional consideration of the transient thermal situation to utilize sensible heat is required. In the case of such a dynamic system, since there is certainly more increased heat capacity of the entire storage system, the volume of the cold energy storage system will be greatly reduced.

• Animal Bioscience
• /
• 제35권3호
• /
• pp.494-502
• /
• 2022

Objective: The objective of this study was to evaluate functional properties of reduced-salt pork meat products made of pre-rigor pork loin treated by different freezing temperatures (-30℃ and -70℃) during storage. Methods: Pre-rigor cured pork loin with 1.0% added salt was compared to post-rigor muscle added with 1.5% salt for pH, color (L^*, a^*, b^*), cooking loss (CL), expressible moisture, warner-Bratzler shear value, thiobarbituric acid reactive substances (TBARS), and volatile basic nitrogen (VBN). Results: Pre-rigor cured pork loins had higher pH and temperature than post-rigor ones as raw meat (p<0.05). pH values were higher for pre-rigor pork loins than those of post-rigor pork loins (p<0.05). Color values did not different among treatments (p>0.05). No color differences were observed during storage period after cooking (p>0.05). The CL (%) of pre-rigor cured pork loins was the lowest when frozen at -70℃. The TBARS and VBN increased from 8 weeks of storage (p<0.05), but no further changed thereafter (p>0.05). Pre-rigor cured pork loins added with 1.0% salt showed similar characteristics to post-rigor pork loins added with 1.5% salt. Conclusion: Cured pork loins could be produced using pre-rigor muscle added with 1/3 of the original salt level (1.5%) and could be stored for up to 4 wks of frozen storage, regardless of a frozen temperature of -30℃ or -70℃ without detrimental effects.

• Ocean and Polar Research
• /
• 제33권3호
• /
• pp.303-308
• /
• 2011

Polar psychrophiles which thrive under extreme conditions such as cold temperature, high salinity, and high dose ultraviolet light, emerge as novel targets for biotechnology. To prevent genetic drift and the possibility of contamination by subculturing, cryopreservation was employed for two psychrophilic microalgae, Porosira sp. (KOPRI AnM0008) and Pyramimonas sp. (KOPRI AnM0046), which have anti-freeze activities. Five cryoprotectants (dimethyl sulphoxide, ethylene glycol, glycerol, methanol and propylene glycol) showed toxicity at 20-30% (v/v). The optimal cryoprotectant concentration and equilibration time were less than 20% and 10 min, respectively. Cryopreservation was carried out in the presence of cryoprotectants either by direct freezing in liquid nitrogen ($LN_2$) or controlled freezing using a controlled rate freezer followed by storage in the $LN_2$ tank. As a result, Pyramimonas sp. (KOPRI AnM0046), a psychrophilic chlorophyta was revived. Cryopreserved Porosira sp. was not revived from either freezing protocols probably due to the silicic cell wall and its relatively large cell size. In the case of Pyramimonas sp. (KOPRI AnM0046), the controlled freezing method showed higher revival yield than the direct freezing method.

• 한국염색가공학회지
• /
• 제21권1호
• /
• pp.10-20
• /
• 2009

The objective of this study is to investigate the efficacy of leaf powder colorants as substitutes for traditional fresh juice extract dyeing. Three kinds of leaf powder colorants were prepared by freeze drying method with or without deep freezing as pre-treatment: one powder colorant from fresh leaf juice with deep freezing; two kinds of powder colorant from fresh leaves with and without deep freezing. Their dyeing properties and storage stabilities were studied and compared with the traditional fresh juice extract dyeing. The presence of indigo in the powder colorants was confirmed by UV/Visible absorption spectra. They showed absorption peak at 602nm which was same with indigo absorption peak. Dyeing was done at low temperature around 6$^{\circ}C$. All three powder colorants produced B colors on silk fabrics, showing similar color to the one dyed traditionally with fresh juice extract. The powder colorants from leaves gave higher color strength than the powder from leaf juice. The powder colorant prepared from leaves with deep freezing was the most stable for long term storage as its color and color strength were not changed after 360 days. So, this was used for further dyeing to study the effects of concentration and repeat dyeing on color strength and colorfastness. Fastnesses to dry cleaning and rubbing were fairly good above 4 rating. Further study is needed to improve light fastness. It was concluded that the leaf powder colorant with deep freezing could be used as a substitute for traditional juice extract dyeing at all seasons.

• 대한토목학회논문집
• /
• 제26권5D호
• /
• pp.813-819
• /
• 2006

미끄럼 저항은 타이어와 도로노면의 마찰저항을 나타내는 지수로 차량의 주행 안전성에 지대한 영향을 미친다. 타이어의 상태, 노면의 마모도, 주행속도, 노면의 건조, 습윤, 결빙 등에 따라 미끄럼저항의 크기는 달라진다. 특히 겨울철 도로노면의 경우 강설 후 기온강하에 도로포장표면이 결빙이 발생할 경우 미끄럼저항이 급격히 저하되며, 미끄럼저항을 회복하고자 제설 작업을 수행하게 된다. 제설작업 후에는 습윤상태로 노면조건이 바뀌게 되는데, 제설제가 노면에 잔류하게 되면 일반적인 습윤상태에서의 미끄럼저항을 확보치 못할 수 있다. 본 연구에서는 국내 포장도로의 대다수를 차지하는 밀입도 아스팔트와 타이닝 콘크리트 포장노면에 대하여 실험실 조건에서 노면 결빙시, 제설중 제설후 잔류물이 노면에 있을 경우의 조건에서의 미끄럼저항을 정량적으로 평가하였다. 연구 결과 노면 결빙시 미끄럼저항 회복시간은 수용액 살포방법이 고체염 살포방법 보다 빠르며 제설제 중에는 소금이 가장 빠르게 나타났다. 노면에 잔류한 제설제는 콘크리트 시편이 아스팔트 시편보다 미끄럼저항 값이 높게 나타났으며 습윤 노면 상태와 비교시 미끄럼저항 확보율은 54~80% 이다.