• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3305-3314
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• 1994

In this study, the influence of a frost formed on the vertical plate for different operating conditions(the temperature of the air, the humidity of the air, the velocity of the air, and the temperature of the cooling plate) is investigated. The performance of the heat exchanger is examined by introducing a parameter such as the energy transfer resistance. Correlations which relate frost density, frost thickness and energy transfer resistance to Reynolds number, air temperature and humidity, and cooling plate temperature are developed. Static pressure drop and air flow rate are expressed as a function of free flow area of air.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1461-1466
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• 2003

This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The characteristics of the frost formation on staggered fin array are somewhat different from those of in-line array. The frost layer at the first fin of the in-line array grows rapidly, compared to second fin, whereas the difference of the frost layer growth between the fins of the staggered array is small. For fin pitch below 10 mm, the frost layer growth of second fin in the staggered array is affected by that of first fin. The frost layer growth and heat transfer of single fin deteriorate with decreasing fin pitch regardless of fin array, however, the thermal performance of a heat exchanger, considering increase of heat surface area, becomes better.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.711-717
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• 2003

This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The frost behaviors of the staggered fin array are somewhat different from those of in-line array. The frost layer formed on the first fin of the in-line array grows rapidly, compared to second fin, whereas the difference of the frost layer growth between the fins of the staggered array is small. For fin pitch below 10 m, the frost layer growth of second fin in the staggered array is affected by that of first fin. The thickness of the frost layer and heat transfer of single fin are reduced with decreasing fin pitch regardless of fin array. However, the thermal performance of a heat exchanger is enhanced due to the increase of heat transfer surface area.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.2
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• pp.66-75
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• 2006

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

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.3
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• pp.138-144
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• 2005

In order to select a new material for a heat exchanger, the frosting behavior of a thermally conductive plastic based on PBT was compared to the frosting behavior of aluminum and three types of plastics based on PTFE. The frosting behavior on the 1 mm thick PBT specimen was similar to that of the aluminum specimen but not that of the pure PTFE specimen. The properties of the frost formed on the specimens were affected by both the thermal conductivity and surface characteristics of the materials. The heat and mass transfer rates of the thermally conductive plastic were almost equivalent to those of the aluminum specimen.

• Journal of the Korean Geotechnical Society
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• v.36 no.8
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• pp.49-60
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• 2020

A fully coupled thermo-hydro-mechanical model is established to evaluate frost heave behaviour of saturated frost-susceptible soils. The method is based on mass conservation, energy conservation, and force equilibrium equations, which are fully coupled with each other. These equations consider various physical phenomena during one-dimensional soil freezing such as latent heat of phase change, thermal conductivity changes, pore water migration, and the accompanying mechanical deformation. Using the thermo-hydro-mechanical model, a sensitivity analysis study is conducted to examine the effects of the geotechnical parameters and external conditions on the amount of frost heave and frost heaving rate. According to the results of the sensitivity analysis, initial void ratio significantly affects each objective as an individual parameter, whereas soil particle thermal conductivity and temperature gradient affect frost heave behaviour to a greater degree when applied simultaneously. The factors considered in this study are the main factors affecting the frost heaving amount and rate, which may be used to determine the frostbite sensitivity of a new sample.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.1-4
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• 2007

This study investigated the applicability of insulation curing method with double layer bubble sheets to the man concrete subjected to cold weather. Temperature history of the mass concrete indicated that the highest temperature of center section was exhibited at $34^{\circ}C$ while the that of surface section was $25^{\circ}C$. Difference between center and surface was shown to be less $10^{\circ}C$ when the temperature of center section was peak section, and thereby associated temperature cracking index was calculated 1.5, and occurrence probability of temperature cracking was 5%, so there was no temperature cracking caused by internal restraint. No temperature crack was observed by naked eye. It was clear that early frost demage and temperature cracking could be restrained due to reducing temperature difference between inner part and outside in the case double bubble sheets applied to insulation curing method in cold weather. The maturity of mass concrete is higher than outside about $72\sim89^{\circ}$ DD, so it was demonstrated to prevent early frost demage and ensure strength excellently. Insulation curing method with double bubble sheets was more economic than heating curing method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.37-39
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• 2010

In this study, with new office construction site of S Construction company as subject, to solve all the problems according to reduced hydration heat and temperature crack of mass concrete used mat foundation and placing time difference, low heat combination of coarse particle cement and fly-ash and setting time difference applied AE water reducing agent, and to prevent the early frost damage caused by low outdoor temperature, a heat insulation method using double bubble sheet was conducted. As a result, it was found that hydration heat and setting time difference was reduced by applying a low heat combination and setting time difference construction method, and that the high insulation capability of the double bubble sheet was able to not only prevent the early frost damage but also reduce temperature difference between the central part and the upper part of mass concrete.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.2
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• pp.79-86
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• 2009

The present study was investigates the effect of the parameters on the frost formation and heat transfer performance such as fin shape, air temperature and air velocity. Heat transfer rate and pressure drop by frost were experimentally investigated. Effect of the wet blub temperature and air velocity on the heat transfer performance has been also investigated. The heat transfer performance of the louver fin and tube type heat exchanger was higher by maximum of 0.85% than the corrugate fin type at the air temperature of $2.0/1.5^{\circ}C$. As the wet blub temperature of air were increased, the heat transfer rate, pressure drop and mass of frost of three test models were increased. Especially, the maximum heat transfer rate and maximum pressure drop were shown for the Type B louver fin heat exchanger. As an experimental result, the enhancement factor(EF) of louver fin and tube type heat exchanger was only $0.2{\sim}0.4$ due to the high pressure drop.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1576-1581
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• 2004

An experimental study has been carried out to investigate the frosting behaviors of thermally conductive plastic(PBT based resin) resin by comparing with those of aluminum and some plastic(PTFE based resin) test specimens. It is found that the frosting behavior of plastic specimens with 1 mm thickness show similar trend with aluminum except PTFE. The properties of frost formed on the specimens are affected by both thermal conductivityand surface characteristics (hydrophilic/hydrophobic) of the materials. It can be said that the heat and mass transfer rate of plastic materials are almost equivalent with those of aluminum.