• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.9-9
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• 2004

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.170-170
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• 2008

• Food Science of Animal Resources
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• v.34 no.1
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• pp.33-39
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• 2014

This study investigates the effects of the gelatin concentration (10-40%, w/v), freezing temperatures (from $-20^{\circ}C$ to $-50^{\circ}C$) and freezing methods on the structural and physical properties of gelatin matrices. To freeze gelatin, the pressure-shift freezing (PSF) is being applied at 0.1 (under atmospheric control), 50 and 100 MPa, respectively. The freezing point of gelatin solutions decrease with increasing gelatin concentrations, from $-0.2^{\circ}C$ (10% gelatin) to $-6.7^{\circ}C$ (40% gelatin), while the extent of supercooling did not show any specific trends. The rheological properties of the gelatin indicate that both the storage (G') and loss (G") moduli were steady in the strain amplitude range of 0.1-10%. To characterize gelatin matrices formed by the various freezing methods, the ice crystal sizes which were being determined by the scanning electron microscopy (SEM) are affected by the gelatin concentrations. The ice crystal sizes are affected by gelatin concentrations and freezing temperature, while the size distributions of ice crystals depend on the freezing methods. Smaller ice crystals are being formed with PSF rather than under the atmospheric control where the freezing temperature is above $-40^{\circ}C$. Thus, the results of this study indicate that the PSF processing at a very low freezing temperature ($-50^{\circ}C$) offers a potential advantage over commercial atmospheric freezing points for the formation of small ice crystals.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.330-335
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• 2014

Purpose: This study was conducted for enhancing the performance of a conventional quick freezer by introducing the supercooling state, using a low-temperature coolant. Methods: In the present investigation, the supercooling process was executed prior to quick freezing for reducing the time by which the temperature passes the zone of maximum ice crystal formation. Every food has different nucleation points and hence, we used silicone oil as the coolant for supercooling for easy modification of temperature. Additionally, for quick freezing, we used liquid nitrogen spray. Results: Using the heat exchanger-type precooler with silicone oil, the temperature of the chamber was easily changed for enabling supercooling. Particularly, the results of the freezing test with garlic indicated that this system improved the hardness of garlic after it was thawed, compared to the conventional freezing method. Conclusions: Before quick freezing, if the food item is subjected to the supercooling state, the time from nucleation to the temperature reaching the frozen state ($-5^{\circ}C$, which is the maximum ice crystal formation zone) will be shorter than that incurred using quick freezing alone. The combination of the heat exchanger-type supercooler and liquid nitrogen sprayer is expected to serve as a promising technology for improving the physicochemical qualities of frozen foods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1466-1473
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• 2012

Soft icecream is made by scraping an ice formed on the inside of the cylindrical evaporator, where R-404A is evaporating in the annulus. The heat transfer characteristics of the refrigerant evaporation and those during icecream formation were experimentally investigated. Results show that the refrigerant-side heat transfer coefficients are highly dependent on the location in the evaporator due to the complex annulus configuration. The heat transfer coefficient at the inlet is generally lower than those of other locations. The average heat transfer coefficient increases as heat flux increases or saturation temperature decreases. A correlation is developed to predict the refrigerant-side heat transfer coefficient. The icecream-side heat transfer coefficient oscillates continuously due to the periodic removal of ice formed on the surface. The average heat transfer coefficient during icecream formation is approximately 280 W/$m^2K$, and that during single-phase cooling increased from 150 W/$m^2K$ to 250 W/$m^2K$.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.1-8
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• 2001

This study was carried out for the purpose of determination of maintenance period and investigation of weak point due to freeze when the gas heater of KOGAS valve station Is not operated in winter season. 3-dimensional non-linear numerical simulation was conducted in order to predict the time and location which bath water in heater reaches to ice point. FLUENT V 5.0, commercial code, is used for thermal fluid flow analysis. We thought this was problem of heat conduction solving the energy equation and modeled gas heater by using the real geometry and scale for performing the 3-dimensional simulation. It was analyzed complex heat transfer phenomena considering convection due to air on surface, conduction in insulation material, natural convection of liquid in heater and heat loss through the pipe.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.597-606
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• 2022

This paper examined the effect of water repellent type and addition among various factors on the deicing performance of cement mortar surface according to incorporation. As a result, the compressive strength of the water repellentcement mortar compared to the cement mortar, and the compressive strength of the oligomer-based water repellent mortar was higher than that of the monomer-based water repellent. The contact angle of the water-repellent mortar was increased compared to the additive mortar, and the oligomer water-repellent agent compared to the monomer-based water-repellent. As a result of measuring the ice formation time of cement mortar due to the mixing of the water repellent, the ice formation was delayed until 25 minutes for mortar to which the water repellent was added. the measurement of the ice attachment load mortar without water repellent with water repellentwhen the water repellent was added to mortar, deicing performance was increased.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.57.1-57.1
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• 2016

Methanol ($CH_3OH$) is a key species in the formation of complex organic molecules. We report the first detection of solid $CH_3OH$ in a line of sight toward the Galactic center (GC) region, based on L-band spectra taken with the Subaru telescope, aided by L'-band imaging data and moderate-resolution spectra from NASA/IRTF. It is found toward a background star, ~8000 AU in projected distance from a newly discovered massive young stellar object (YSO). This YSO also exhibits a strong $CO_2$ ice absorption band at ${\sim}15{\mu}m$ in Spitzer/IRS data, which has a prominent long-wavelength wing. It confirms that a high $CH_3OH$ abundance is responsible for the broad $15{\mu}m$ $CO_2$ ice absorption towards massive YSOs in the GC. Clearly, $CH_3OH$ formation in ices is efficient in the GC region, as it is in star-forming regions in the Galactic disk. We discuss implications of our result on the astrochemical processes in the hostile GC molecular clouds.

• Journal of ILASS-Korea
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• v.16 no.3
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• pp.146-151
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• 2011

LPG(Liquified Petroleum Gas) fuel for vehicles has lots of advantages such as low emission level, cheaper fuel cost and enough infrastructure. Therefore it arouses interest as an alternative engine to reduce emission of diesel engines. Especially MPI(Multi Point Injection) type LPLi(Liquid Phase LPG injection) system could have overcome the disadvantages of mixer types such as low engine performance, decreased charging efficiency and cold starting difficulty. However ice formation on the nozzle tip and intake port due to the freezing of moisture around the components is often observed in LPLi systems. This icing phenomenon is the direct cause of unstable engine combustion, resulting in engine emissions. Therefore in this research, a spray visualization test for LPG injection was carried out to obtain the basic information of an LPLi injector, then the effects of butane and propane mixing rates on ice formation at the intake port and nozzle tip was investigated. As a result, the icing characteristics of them showed contrary results according to the mixing rates.

• Integrative Medicine Research
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• v.6 no.1
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• pp.12-18
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• 2017

Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research as well as for many medical applications, cannot be stored with simple cooling or freezing for a long time because ice crystal formation, osmotic shock, and membrane damage during freezing and thawing will cause cell death. The successful cryopreservation of cells and tissues has been gradually increasing in recent years, with the use of cryoprotective agents and temperature control equipment. Continuous understanding of the physical and chemical properties that occur in the freezing and thawing cycle will be necessary for the successful cryopreservation of cells or tissues and their clinical applications. In this review, we briefly address representative cryopreservation processes, such as slow freezing and vitrification, and the available cryoprotective agents. In addition, some adverse effects of cryopreservation are mentioned.