• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.6
• /
• pp.477-485
• /
• 2006

A study on frost prevention of fin-tube heat exchanger is experimently performed by spreading antifreezing solution on heat exchanger surface. It is desirable that the antifreezing solution spreads completely on the surface forming thin liquid film to prevent frost nucleation and crystal growth and to reduce the thermal resistance across the liquid film. A small amount of antifreezing solution falls in drops on heat exchanger surface using two types of supplying devices, and a porous layer coating technique is adopted to enhance the wettedness of antifreezing solution on the surface. It is observed that the antifreezing solution liquid film prevents fin-tube heat exchanger from frosting, and heat transfer performance does not degrade through the frosting tests. The concentration of supplied antifreezing solution can be determined by heat transfer analysis of the first row of heat exchanger to avoid antifreezing solution freezing due to dilution by moisture absorption.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.5
• /
• pp.459-467
• /
• 2005

The effect of anti freezing solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreezing solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation and reduce the thermal resistance across the film. A porous layer coating technique is adopted to improve the wettedness of the anti freezing solution on a parallel plate heat exchanger. The antifreezing solution spreads widely on the heat exchanger surface with 100 $\mu$m thickness by the capillary force resulting from the porous structure. It is observed that the antifreezing solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by thin liquid film are only $1\~2\%$ compared with those for non-liquid film surface.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.1
• /
• pp.68-72
• /
• 1995

• 한국도로학회:학술대회논문집
• /
• 2001.10a
• /
• pp.57-63
• /
• 2001

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.21 no.6
• /
• pp.486-501
• /
• 1992

• Korean Journal of Plant Tissue Culture
• /
• v.27 no.4
• /
• pp.339-343
• /
• 2000

When plants are exposed to subfreezing temperatures ice crystals are forming within extracelluar space in leaves. The growth of ice crystal is closely related to the degree of freezing injury. It was shown that an antifreeze protein binds to an ice nucleator through hydrogen bonds to prevent growth of ice crystal and also reduces freezing damage. The antifreeze proteins in plants are similar to PR proteins but only the PR proteins induced upon cold acclimation were shown to have dual functions in antifreezing as well as antifungal activities. Three of the genes encoded for CLP, GLP, and TLP were isolated from barley and Kentucky bluegrass based on amino acid sequence revealed after purification and low temperature-inducibility as shown in analysis of the protein. The deduced amino acid of the genes cloned showed a signal for secretion into extracellular space where the antifreezing activity sup-posed to work. The western analysis using the antisera raised against the antifreeze proteins showed a positive correlation between the amount of the protein and the level of freeze tolerance among different cultivars of barely. Besides it was revealed that TLP is responsible for a freeze tolerance induced by a treatment of trinexapac ethyl in Kentucky bluegrass. Analysis of an overwintering wild rice, Oryza rufipogon also showed that an acquisition of freeze tolerance relied on accumulation of the protein similar to CLP. The more direct evidence for the role of CLP in freeze tolerance was made with the analysis of the transgenic tobacco showing extracellular accumulation of CLP and enhanced freeze tolerance measured by amount of ion leakage and rate of photosynthetic electron transport upon freezing. These antifreeze proteins genes will be good candidates for transformation into crops such as lettuce and strawberry to develop into the new crops capable of freeze-storage and such as rose and grape to enhance a freeze tolerance for a safe survival during winter.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.205-208
• /
• 2007

We aim to develop antifreezing coolant used to in the 200kW Fuel Cell system that is possible to starting at low temperature and that must not to be freezed under $-30^{\circ}C$, have high coductivity, excellent system protection ability and durability.

• Proceedings of the SAREK Conference
• /
• 2004.06a
• /
• pp.17-17
• /
• 2004

• Journal of the Korea Concrete Institute
• /
• v.19 no.5
• /
• pp.647-653
• /
• 2007

In ready mixed concrete factory, in case of using the high molecular additive in winter especially the liquid additive for the early strength, it is required to check the stability. In this research, the freezing and gelling characteristics of the liquid additive for the early strength is reviewed, the material and mechanical solution are proposed to that the practical quality control method will be suggested. As the result, the Freezing temperature of the liquid additive for the early strength is $-11.8^{\circ}C$, and it is the lower than the temperature at which the strength is shown. By making with sodium silicate of $37{\pm}0.5%$ designed by $SiO_2\;and\;Na_2O$ in 0.31 of mol ratio, it minimizes the gelling at the lower temperature. On the other hand, facilities for storing and supplying the material should be set at $40^{\circ}C$ so the temperature distribution is well spreaded for practical operation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.861-865
• /
• 2000

During the placement of concrete in cold weather, there are serious problems due to frozen concrete in the early stage. These adverse effects prevent the hardening of concrete. There are special mixing, handling, placement and crying to minimize problems. Heat crying and sheet curing have been used in crying steps in order to reduce problems. However, these curing methods are not efficient because it is hard to obtain the good quality and strength of concrete, and moreover, it needs additional works for curing. In this study, we evaluate the application of cold weather concrete by the dose antifreezing admixture in concrete mix design. Because it is easy to handle inconstruction site and improve the quality of concrete. As the result of this paper is to present a successful case for the practical use of cold weather concrete.