• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.70.2-70.2
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• 2019

Strong radiation fields can change the ionization state of metals and hence cooling rates. In order to understand their effects on the momentum transfer from radiation and supernova feedback, we perform a suite of radiation-hydrodynamic simulations with radiation-modulated metal cooling. For this purpose, we pre-tabulate the metal cooling rates for a variety of spectral shapes and flux levels with the spectral synthesis code, Cloudy, and accurately determine the rates based on the local radiation field strength. We find that the inclusion of the radiation-modulated metal cooling decreases the total radial momentum produced by photo-ionization heating by a factor of ~3 due to enhanced cooling at temperature T~10^3-4 K. The amount of momentum transferred from the subsequent SN explosions, however, turns out to be little affected by radiation, as the main cooling agents at T~10^5-6 K are only destroyed by soft X-ray radiation which is generally weak. We further discuss the total momentum budget in various conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.8
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• pp.672-677
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• 2006

The steady cooling characteristics of a cryochamber for infrared (IR) detector have been investigated analytically, considering radiation shields. The thermal modeling considers the conduction heat transfer through cold finger, the gaseous conduction due to out-gassing, and the radiation heat transfer. The cooling load of the cryochamber is obtained by using a fin equation. The results obtained indicate that the gaseous conduction plays an important role in determining the steady cooling load. The steady cooling load is increased as the gas pressure is increased. It is also found that the cooling load is substantially decreased with a radiation shield. The most thermal load of a cryochamber occurs through the cold finger.

• Journal of the Korean housing association
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• v.10 no.4
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• pp.111-120
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• 1999

The purpose of this study is to evaluate the efficiency of the thermal environment created by the cooling system at the apartment that combines the forced convection cooling(the system reducing humidity from room) with the floor cooling radiation which uses the floor panel from floor heating system, a general residential heating system in Korea. In this study, the combined cooling system in which air supply, spurt temperature difference and interior draft are reduced, is compared with the existing forced convection cooling system. To identify the effect of the comparison concretely, a comparative experiment is carried out on tour conditions, ie, convection cooling, floor radiation convection cooling and floor radiation cooling. Through it the characteristical thermal environment formed within the model room is analyzed, and the conveying system of compressed floor chill and condensation problem are reviewed.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.68-72
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• 2002

This work investigates the transient cooling characteristics of an Infrared (IR) detector cryochamber, which has a critical effect on the cooling load. The current thermal modeling considers the conduction heat transfer through a cold well. the gaseous conduction due to outgassing. and the radiation heat transfer. The transient cooling Performance. i.e. the penetration depth and cooling load, is determined using a finite difference method. It is found that the penetration depth increases as the bore conductivity increases. Gaseous conduction and radiation hardly affect the penetration depth. The transient cooling load increases as the bore conductivity increases. The effects of gaseous conduction and radiation on transient heat transfer are weak at initial stages of cooling. However, their effects become significant as the cooling Process Proceeds.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.174-177
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• 2003

Cooling load from the top plate to L$N_2$ surface, including wall conduction, gas conduction, radiation, and current leads, is investigated in a closed cooling system for HTS transformer. In general methods of load calculation, individual load is estimated separately, but they are actually coupled each other because of natural convection of nitrogen vapor. Using heat transfer analysis, we calculate cooling load with taking into account the effect of natural convection. Cooling load is under- estimated approximately 2 ％ when the natural convection is ignored. If the operating current is high, there will be a wide difference between actual cooling load and cooling load by individual calculation. Cooling load decreases with increasing number of radiation shield. With production, construction, and cooling load, three radiation shields are proper to 1 MVA HTS transformer.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.49.3-50
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• 2015

Synchrotron radiation of relativistic electrons is an important radiation mechanism in many astrophysical sources. In the sources where the synchrotron cooling timescale is shorter than the dynamical timescale, electrons are cooled down below the minimum injection energy. It has been believed that such fast-cooling electrons have a power-law distribution in energy with an index -2, and their synchrotron radiation has a photon spectral index -1.5. On the other hand, in a transient expanding astrophysical source, such as a gamma-ray burst (GRB), the magnetic field strength in the emission region continuously decreases with radius. Here we study such a system, and find that in a certain parameter regime, the fast-cooling electrons can have a harder energy spectrum. We apply this new physical regime to GRBs, and suggest that the GRB prompt emission spectra whose low-energy photon spectral index has a typical value -1 could be due to synchrotron radiation in this moderately fast-cooling regime.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.6
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• pp.543-550
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• 2003

In order to saving the energy for HVAC system of buildings, utilization of wind-induced cross ventilation is thought to be promising. However, utilization of natural ventilation alone is not sufficient for maintaining the human thermal-comfort such as in hot and humid regions. A hybrid air conditioning system with a controlled natural ventilation system, or combination of natural ventilation with mechanical air conditioning is thought to overcome the deficiency of wind-driven cross ventilation and to have significant effects on energy reduction. This paper describes a concept of hybrid system and propose a new type of hybrid system using radiational cooling with wind-induced cross ventilation. Moreover, a radiational cooling system is compared with an all-air cooling system. The characteristics of the indoor environment will be examined through CFD (Computational Fluid Dynamics) simulation, which is coupled with a radiation heat transfer simulation and with HVAC control in which the PMV value for the human model in the center of the room is controlled to attain the target value.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.66-71
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• 2009

The solar photovoltaic power generator can get more power with the higher solar radiation quantity. However, if the higher solar radiation quantity on cell becomes high temperature, the efficiency of generate will be reduced. To install cooling system for this kind of device can be the way to solve high temperature problem on cell but another problems after install it such as increasing of solar generated quantity problem cost to install cooling system and cost to be maintained cooling system weren't discussed to practical use this system. So the present paper described about effect and commercial business possibility of cooling system. After installing a cooling system the results of experiment about 5.76[%] average annual increasing of solar photovoltaic can expect.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.27-32
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• 2011

Most of domestic building generally don't have fixed shading devices considering of appearance and aesthetic issues. In this study is suggested that tilt window simultaneously has a role of shading and blocking solar radiation. The tilt window thermal performance is investigated by relation ship between inclination and heating cooling road. As comparing vertical window with $5^{\circ}$ and $7^{\circ}$ of tilt window respectively, the heating load is increased by 3.6% and cooling load is reduced by 8.1% on $5^{\circ}$ tilt window and the heating load is increased by 5.3% and cooling load is reduced by 11.5% on $5^{\circ}$ tilt window. Especially, the total load of alternative tilt window is showed the reduction rate 2.6% and3.6% compared of vertical window. Therefore, the tilt window is possible to role of shading of solar radiation and reduction of heating and cooling load.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.189-192
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• 2008

The solar photovoltaic Power generator can get more power with the higher solar radiation quantity. However, if the higher solar radiation quantity on cell becomes high temperature, the efficiency of generate will be reduced. To install cooling system for this kind of device can be the way to solve high temperature problem on cell but another problems after install it such as increasing of solar generated quantity problem, cost to install cooling system and cost to be maintained cooling system weren't discussed to practical use this system. So the present paper described about effect and commercial business possibility of cooling system.