• Polymer(Korea)
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• v.29 no.1
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• pp.91-95
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• 2005

The PVA hydrogels were prepared by the chemical and irradiation method to improve the heat resistance of these hydrogels at the high temperature. The physical properties such as the gel content, the degree of swelling and the gel strength for the synthesized hydrogels were examined. Gel content increased as the chemical reaction time and the irradiation dose increased, and gel content of the hydrogels were higher when the two-steps of chemical and irradiation method were used rather than only the chemical method. Gel strength increased as the chemical reaction time increased, and as the irradiation dose decreased. The hydrogels prepared by the chemical reaction for 5 hours and the two-steps had the heat resistance at the high temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.556-565
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• 1995

The physical model of interest is based upon the concentric cylinder, where the outside cylinder is filled with optically thick and high temperature phase change material(PCM). The fluid is flowing through the inside cylinder to transfer the appropriate energy. The fluid is flowing through the inside cylinder to transfer the appropriate energy. The governing equations for the phase change material including internal thermal radiation and for the turbulent transfer fluid have been employed and numerically solved. The optically thick phase change justifies the P-l spherical harmonics approximation, which is believed to be appropriate choice particularly for the much coupled problem like in this study. The solid/liquid interface, temperature distribution within the PCM and the heat flux from the PCM to the transfer fluid have been obtained and compared with those of laminar transfer fluid. The numerical results show that the turbulent transfer fluid accelerates the solid/liquid interface and results in the increase of heat transfer rate from the PCM. The internal thermal radiation within the PCM, however, does not always playa role to increase the heat transfer rate throughout the inside cylinder. It is believed that the combined heat flux has been picked up more in the inflowing area than in the pure conductive phase change material.

• Journal of the Korean Solar Energy Society
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• v.36 no.4
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• pp.1-9
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• 2016

The purpose of this study was to compare heat shading performance of various blind types in summer. 4 types of blinds were employed and the results are summarized as follows: 1) There were significant differences in indoor thermal environment and heat shading performance between different heat shading devices, and functional blinds demonstrated relatively superior heat shading performance. 2) Indoor long wave radiation influx measures were lowest for the coating roll blind (Blind B), followed by the coating venetian blind (Blind C), the venetian blind (Blind A), the roll blind, and not having any blinds at all. 3) Such examination results carry implications to reduce cooling load and enhance the indoor environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.937-944
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• 2004

An experimental study has been conducted to evaluate the effects of $CO_2$ on heat transfer from oxygen-enriched hydrogen flame. Experiments were performed on flames stabilized by a co-flow swirl burner, which was mounted on top of the furnace. Five different oxidizer compositions were prepared by replacing $N_2$ with $CO_2$. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace have been measured using a heat flux meter. Temperature distribution in furnace also has been measured and compared. By increasing $CO_2$ proportion in the oxidizer, the convection played a more significant role rather than radiation. Overall temperature in the furnace was seen to be decreased, while the total heat flux has increased.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.247-250
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• 2015

The characteristics of opposed nonpremixed tubular flames with radiation heat loss are investigated using linear stability analysis and 2-D numerical simulations. Two extinction limits, as the $Damk{\ddot{o}}hler$ number is small or large, are confirmed using finite difference method with a simple continuation method. It is verified that the results of linear stability analysis predict the number of flame cells and the critical Da starting cellular instability or amplification of temperature near both extinction limits with good resolution.

• Journal of the Korean Society of Clothing and Textiles
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• v.1 no.1
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• pp.25-29
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• 1977

The warmth retentivity of natural and syntheic waddings as bedding stuff, and further, the machanism of heat transmission through conduction, radiation and convection were analysed. The materials used were cotton, silk, and wool as natural waddings, and polyamide, polyester, regular acrylic, conjugate acrylic, regular polyprepylene and conjugate polypropylene as synthetic waddings. The results of this study are as follow: 1. The warmth retentivity is highest in silk. Following silk in descending order is cotton, conjugate acrylic, polyester, regular acrylic, wool, polyamide, conjugate polypropylene and regular polypropylene. There is not any significant relationship between warmth retentivity and the conductivity of the fibers. 2. Transmission by radiation through the fiber waddings is highest in conjugate polypropylene. Following conjugate polypropylene in descending order is regular polypropylene. polyester. polyamide, conjugate acrylic, regular acrylic, wool, cotton, and silk. This is seen to be in nearly reversed order to the abovementioned order of warmth retentivity. In this respect, warmth retentivity with loose fibreous material as in the case of bedding stuff is primarily affected by the interceptive function of the fibers in heat radiation. 3. Warmth retentivity becomes lower with increasing air content of the waddings. This is because heat transmission by radiation incrases as air content increases. The air content increase is due to the fact that the air is unable to intercept heat radiation. In addition, heat transmission accelates in proportion to the increase in convection as the air gap enlarges.

• International Journal of Aeronautical and Space Sciences
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• v.3 no.1
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• pp.95-104
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• 2002

Numerical solution of the full Navier-Stokes equation as well as the energy equation has been obtained for the unsteady natural convection in a rectangular enclosure. One side wall was maintained at very high temperature simulating fires. Especially the effect of surface radiation was taken into account. While the enclosed air was assumed to be transparent, the internal walls directly interacted one another through the surface radiation. Due to a significant temperature difference in the flow field, the equation of state was used instead of the Boussinesq approximation. It was found that the rapid heating of the adiabatic ceiling and floor by the incoming radiation from the hot wall made the evolution at thermo-fluid field highly unstable in the initial period. Therefore, the secondary cells brought about at the floor region greatly affected the heat transfer mechanism inside the enclosure. The heat transfer rate was augmented by the radiation, resulting in requiring less time for the flow to reach the steady state. At the steady state neglecting radiation two internal hydraulic jumps were clearly observed in upper/left as well as in lower/right comer. However, the hydraulic jump in the lower/right comer could not be observed for the case including radiation due to its high momentum flow over the bottom wall. Radiation resulted in a faster establishment of the steady state phenomena.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.113-118
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• 2011

In order to prevent incoming solar radiation, it is necessary to study about blinds' blocking out effects of heat that are installed at the balcony at an apartment house. To figure out the heating effects from the windows, a study for indoor thermal environment according to the location of blinds is also needed. In order to find out the changes of indoor thermal environment, we'll compare models of a house building with or without Venetian blinds: one place has an extended living room removing a balcony and another one has a normal balcony. The result is as follows. Without blinds, the place with an extended living room has benefits for saving heat compare to the place with a normal balcony. It's because the warm air heated by the incoming solar radiation moves into the living room through convection current and radiation which causes an increase of the indoor temperature. At an extended living room, the temperature difference from outside and inside, when blinds were installed inside, was $1.9^{\circ}C$ while it was $0.6^{\circ}C$ when the blinds were installed at outside of the balcony. It is evaluated that setting up the blind outside prevents much heat. At the space with a normal balcony, installing blinds at living room windows can save much heat compare to installing blinds at windows at the balcony. The indoor temperature was low when blinds were installed. It can be said that blinds block heat from the incoming solar radiation. Moreover, when blinds are installed, there is a big change of indoor temperature due to the radiation from the blinds' slat and convective activities in between the blinds and windows. This also has to be considered.

• Korean Journal of Environmental Biology
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• v.26 no.1
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• pp.1-7
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• 2008

A mathematical model for the synergistic interaction of physical and chemical environmental agents was suggested for quantitative prediction of irreversibly damaged cells after combined exposures. The model took into account the synergistic interaction of agents and was based on the supposition that additional effective damages responsible for the synergy are irreversible and originated from an interaction of ineffective sublesions. The experimental results regarding the irreversible component of radiation damage of diploid yeast cells simultaneous exposed to heat with ionizing radiation ($^{60}Co$) or UV light (254 nm) are presented. It was shown that the cell ability of the liquid holding recovery decreased with an increase in the temperature, at which the exposure was occurred. A good correspondence between experimental results and model prediction was demonstrated. The importance of the results obtained for the interpretation of the mechanism of synergistic interaction of various environmental factors is discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.382-390
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• 1992

The problem of natural convection from a vertical fin is solved by coupling the thermal diffusion equation in the fin to the constitutive equations of the ambient medium involving the radiation of the medium. The analysis is accomplished by employing an integral method. The governing equations for the problem are solved by shooting method based on the Runge-Kutta Scheme at Pr= 0.7. For the range of values of the fin parameter and the radiation-conduction parameter in the analysis, the numerical results show that the radiation effects play an important role in the heat transfer and enhance the heat transfer.