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

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.798-803
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• 2009

In this study, dimensionless correlations of frost properties (i.e. the thickness and surface temperature of frost) on heat exchanger fin with nonuniform temperature distribution are proposed from frosting experiments. We analyzed the local fin temperature distribution, frost thickness and frost surface temperature on a 2D fin; in the airflow direction and the direction perpendicular to airflow. As a result, the frost growth on the fin had a close relation with fin heat conduction. The dimensionless correlations for the average frost properties were expressed as a function of dimensionless temperature, humidity ratio, Reynolds number, and Fourier number. These correlations agreed well with experimental data with the error less than 14%.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1402-1408
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• 2020

In order to save energy, a lot of research has been conducted to develop a high-efficiency heat pump. Research to reduce or eliminate the occurrence of frost in the outdoor unit coil is also being conducted at the same time. A constant temperature chamber was constructed that allows experimentation under the same conditions as in the natural state so that frost does not occur in the outdoor unit of the heat pump regardless of the season. In order to verify the validity of the experimental apparatus, a simulation was conducted by dividing the straight length of the duct in front of the outdoor unit in the constant temperature chamber, which is the experimental apparatus, into three conditions. As a result, it was found that a straight space must be secured 10 times the diameter of the duct.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2738-2743
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• 2008

We conducted a study by computational simulation about the effects of frost thickness on the pressure drop and heat transfer characteristics as whole heat exchanger configuration changes. In order to perform the analysis for validation, we assumed that frost properties have constant values and the frost layers that are formed on the fin and tube surfaces are uniform. In order to find the constant thermal conductivity of frost layer, a variety of frost thermal conductivities are performed in our work and compared with the results by Lee et al. [4] and Yang et al. [5] proposed many experimental data about the 2-rows and 2-columns finned tube heat exchanger. The numerical results agreed well with the experimental data when frost conductivity is 0.07W/mK. After the validation had performed, we applied this procedure to the finned tube heat exchanger of domestic refrigeration and investigated the thermo-hydraulic characteristic of the heat exchanger affected by frost thickness according to the inlet velocities and temperatures of air considering the configuration change such as fin pitch.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.3
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• pp.123-128
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• 2022

A lot of research is being done to develop a high-efficiency heat pump to save energy, and research to reduce or eliminate the phenomenon of frost occurring in the outdoor unit coil is also being conducted at the same time. In order to conduct a study that does not cause frost on the outdoor unit of the heat pump regardless of the season, a constant temperature chamber like a general room that can be tested under the same conditions as in the natural state was built. The experiment was conducted by providing an environment similar to the natural state to the outdoor unit of the heat pump installed in the constant temperature chamber. As a result, the lower the outdoor temperature, the lower the efficiency of the heat pump. It wat confirmed that the lower the value, the longer it is.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.3
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• pp.140-146
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• 2023

A lot of research is being done to develop a high-efficiency heat pump to save energy. Among them, research to reduce or eliminate the phenomenon of frost occurring in the outdoor unit coil are being conducted at the same time. A constant temperature chamber that can be tested under the same conditions as natural conditions was constructed to conduct research that does not cause frost on the outdoor unit of the heat pump regardless of the season. The outdoor unit of the heat pump installed in the constant temperature chamber was simulated under the same natural conditions. As a result, it was confirmed that the mass flow rate of the refrigerant decreased as the outdoor temperature decreased, and the dryness of the refrigerant also increased linearly with the outdoor temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.105-112
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• 2011

The objective of this study is to predict the heat-transfer performance of a spirally coiled circular fin-tube evaporator in which either R134a or R600a was used; this heat-transfer performance was predicted by varying the mass flow rate, inlet air temperature, air flow rate, and tube thickness. Mean deviation for the analytical model from the measured data was ${\pm}8.3%$. Simulation results revealed that at a given mass flow rate, the heat-transfer rate of the evaporator using R600a was higher than that usingR134a because the enthalpy of the former is higher than that of the latter at the given conditions. The heat-transfer rate of both refrigerants increased with an increase in the air flow rate and inlet air temperature but decreased with an increase in the tube thickness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.515-522
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• 2010

The objective of this study is to investigate the air-side heat transfer characteristics of a spirally-coiled circular fin-tube heat exchanger for various geometric parameters under non-frosting conditions. The heat transfer characteristics of the heat exchanger were analyzed with respect to heat exchanger geometries, and then, the characteristics were compared with those of rectangular-plate fin-tube heat exchangers with discrete fins. The heat transfer coefficient increased with a decrease in the number of tube rows and an increase in the fin pitch. The optimum length of the L-foot was 2.7 mm. In addition, the heat transfer rate increased with a decrease in the tube pitch and the tube thickness. The heat transfer coefficient of the spirally-coiled circular fin-tube heat exchanger was 24.3% higher than that of the rectangular-plate fin-tube heat exchanger.

• Korean Journal of Veterinary Service
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• v.30 no.3
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• pp.445-457
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• 2007

This report studied the individual number, their favorite habitat, and change pattern of family and group number in Cheolwon Basin, starting in the early Oct. 2004 until late March. 2005 to investigate the ecological features of the Red-crowned Crane and the White-naped Crane. The Cranes arrived Cheolwon Basin in mid-October until next mid-March, and passed the winter in mid-November until next late-February The most visiting number amounted to 550 individuals and, that period was the most frosting mid-January to mid-February. The White-naped Crane visited Cheolwon Basin in autumn, the early winter and spring. Approximately, the wintering-number is 550 individuals, also, the mid-March was the peak-period of arrival and, the number amounted to 2,162 individuals. The cranes chose the farming area around mountains as their wintering habitat and were less likely to choose the farming area around lake as habitat. The Red-crowned Crane and the White-naped Crane showed the different periodical pattern in familial and group numbers. In case of the crane, the familial pattern was stable, but varied in grouping number, and this pattern was similar to the variation of overall individual number. And, also, the most grouping number was shown in the most freezing period of wintering period. The White-naped Crane showed the similar pattern of the Red-crowned Crane that is, stable family number and varying group number, this pattern affected the total number of entire individuals. Grouping number increased in migration period. Parasite infection rate is G japonensis 35.0%, G vipio 38.7%.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.227-232
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• 2008

The present study was investigated the local heat transfer characteristics and temperature distribution on the louver fin by using the expansion model. Heat transfer rate, frost mass and temperature distribution of the louver fin under frosting condition were experimentally investigated. Local heat transfer rate and heat flux on the louver were analyzed by the conduction heat transfer between top and lower part of the louver. The experimental key parameter was brine inlet temperature(-5, -10, $-15^{\circ}C$). The heat transfer performance and frost mass at brine temperature of $-15^{\circ}C$ were increased by maximum 3 time than the brine temperature of $-5^{\circ}C$. At all experimental case, local heat transfer rate and heat flux of the louver were almost symmetry at the louver number of 6. Especially, local heat transfer rate and heat flux were maximum increased on the louver number of 4 and 8.