• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.97-104
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• 2017

Reinforcement of insulation in apartment buildings reduces the heating and cooling energy consumption by lowering the heat transfer in the building envelope. There are differences between internal and external insulation methods in heat transmission properties. However, some building load calculation programs cannot analysis the differences between the two. This is because these programs do no account for the timelag or thermal storage effect of the wall according to the location of insulation. In this study, the heat transmission characteristics of internal and external insulation were analyzed by EnergyPlus, and heating and cooling energy demand was compared. The results showed that external insulation system had lower heating and cooling loads than internal insulation system. Also the heat transfer rate of external insulation is steadier than internal insulation. About 13.6% of heating and cooling energy demand decreased when the outdoor wall was finished with external insulation compared to the demand with internal insulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.577-588
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• 1995

A numerical study is made on the melting process of an unconstrained ice inside an isothermal ice-ball capsule. The unmelted ice core is continuously ascending on account of buoyancy forces. Such a buoyancy-assisted melting is commonly characterized by the existence of a thin liquid film above the ice core. The present study is motivated to present a full-equation-based analysis of the influences of the initial subcooling and the natural convection on the fluid flow associated with the buoyancy-assisted melting. In the light of the solution strategy, the present study is substantially distinguished from the existing works in that the complete set of governing equations in both the melted and unmelted regions are resolved in one domain. Numerical results are obtained by varying the wall temperature and initial temperature. The present results reported the transition of the flow pattern in a spherical capsule, as the wall temperature was increased over the density inversion point. In addition, time wise variation of the shapes for the liquid film and the lower ice surface, the time rate of change in the melt volume fraction and the melting distance at symmetric line is analyzed and is presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.814-819
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• 2008

The purpose of this study was developing the building materials for creation the comfortable IAQ. By reducing formaldehyde(HCHO) known as the main factors of Sick House Syndrome. This material must be revealed the physical and eco-friendly performance, so this study set up the basic standards for building materials. The source of physical performance evaluation is Korea Industrial Standards and the base of environmental ability is the Eco Label considering certificated system related to an apartment house. Because the developed material was satisfied with the established standards, it was tested in mock-up room for obtaining the real date from indoor air. The mock-up test was conducted according environmental standard method for indoor air Quality of the ministry of environment. The result of this study were as follows; the functional building materials had a effect to reduce the formaldehyde concentration for a initial period without wall paper, so additional development is needed for application with the wall paper and the available period.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.10
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• pp.689-695
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• 2008

Experimental study has been performed to investigate the influence of non-condensible gas(NCG) charged mass on the thermal performance of a variable conductance heat pipe(VCHP) with screen mesh wick. The VCHP is furnished by screen mesh number 200 for the pipe outer diameter of 12.7mm and the pipe length of 500 mm. The VCHP is filled with water as working fluid of 4.8g and nitrogen as NCG and has evaporator, condenser and adiabatic section, respectively. For the results from experiment, it is found that, for the same charged mass of working fluid, the overall wall temperatures of heat pipe grows up with increasing NCG charged mass. The variation of operating temperature of VCHP reduces with increasing NCG mass. In addition, the profile of axial wall temperature distribution is presented for heat transport capacity of heat pipe, the temperature of cooling water of condenser, inclination angle, and operating temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.75-82
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• 2000

This paper presents the predicted results by CFD technique of air flow and contaminant distribution in a full-scale kitchen opened to a living room, ventilated by a exhaust hood. To analyze the characteristics of the indoor environment, the concept of contaminant index was defined. In this study, the locations of the gas range and the window were chosen as the parameters to investigate the indoor environment. The values of the contaminant index for several layout of the gas range and the window were calculated and compared. When the gas range is installed along the wall with specified window location, its position in relation to the wall has unnoticed effect on contaminant infer. Once the location of the gas range is fixed, the indoor air quality may deteriorate by the proximity of the window to the gas range. This is due to the shorter distance that external fresh air must travel within the kitchen before it reaches the exhaust fan.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.633-641
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• 1999

Experiments were carried out to investigate the condensation heat transfer characteristics for R22 and its alternatives, R407C (R32/125/134a, 23/25/52wt%) and R410A (R32/125, 50/50wt%). A concentric tube heat exchanger was made to conduct condensation heat transfer tests. Mass flux and saturation temperature of refrigerants at the test section inlet were varied to get the corresponding heat transfer coefficients. Serial and parallel input of secondary fluid (water) were applied to the test subsections. Compared with existing correlations of condensation heat transfer, experimental heat transfer coefficients obtained in this study were generally higher than the predicted values, and mean absolute deviations from several correlations were shown. Wall subcooling was introduced to get a new correlation for condensation heat transfer coefficients by modifying Shah's equation. The RMS deviation of the measured heat transfer coefficients from the new correlation in this study for R22 is 9.9% and that for R407C and R410A are 10.2% and 14.6%, respectively.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.13 no.3
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• pp.148-156
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• 1984

The effect of inclination on the steady, two-dimensional, laminar natural convection in rectangular enclosures with localized heating from below has been investigated numerically. The enclosure was uniformly heated with a partial heat source at the center of the bottom wall and cooled from the upper wall while the other walls were insulated. The governing equations were solved numerically by using the ADI finite difference method with the SOR method. The computations were carrid out with air, Pr =0.733, in the Grashof number range, $1\times10^4\~3\times10^4$, for the inclination of the enclosures was varied from $0^{\circ}\;to\;90^{\circ}$. The effects of Grashof number and aspect ratio on the inclination for the transition of the flow pattern in enclosures were determined. From the results, it was found that the transition angles of the flow in the enclosures were greater in localized heating than in uniform heating from below, and that the inclination was to strongly effect on the heat transfer and the flow pattern within the enclosure.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.608-613
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• 2009

According to the building regulation U-value limitation of window is $3.3W/m^2{\cdot}K$ in southern regions, while U-value limitation of wall is $0.35{\sim}0.58W/m^2{\cdot}K$. It means that the energy loss through windows is five times more than it through wall. Therefore, this study analyze how much it has affected building energy rating when the insulation performance of windows and walls is changed by building regulation. In conclusion, in order to obtain 2 rating thermal performance of windows is improved more than 10 percent of U-value limitation and it of wall is improved more than 20 percent. The thermal performance of windows is improved more than 20 percent of U-value limitation and it of wall is improved more than 30 percent to receive 1 rating.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.730-735
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• 2009

The purpose of this study is to consider improvement performance to prevent condensation and draw the optimum insulation design method for building using simulation tool. In this study, the three corners, weak part in condensation, were conducted by three-dimensional steady state simulation. From the results, it is required to strengthen insulation design, and it is founded that existing insulation system typically applied to most Korean apartment buildings has serious insulation defect that insulation is disconnected by structural components at the joints of wall-slab and wall-wall in envelope. So, it is considerate to need a concrete technology improvement.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.841-846
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• 2009

Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied several impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.