• 설비공학논문집
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• 제3권5호
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• pp.376-385
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• 1991

The purpose of this paper is to propose basic data on convection heat-transfer coefficients in Ondol-heated room. Surface temperatures and several temperatures around each inside surface of wall, floor and ceiling composed of heating room are measured vertically in Ondol-heated model rooms, and the vertical temperature profiles could be expressed by nonlinear equation models. Also, the convection heat transfer phenomena are analysed from the nonlinear equation models. In the results, the convection heat-transfer coefficients of Ondol heated space are suggested by the term of temperature difference between each wall surface and room air temperature and by the relationship between Nusselt number and Rayleigh number of dimensionless numbers.

• 설비공학논문집
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• 제13권3호
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• pp.160-166
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• 2001

A numerical analysis has been performed for natural convection in an air conditioner duct system. The governing equations were solved a finite volume method using a SIMPLE algorithm. In the calculation mode of duct, the room temperature was preserved at $25.0^{\circ}C$ and duct wall temperature had a temperature of 15, 20.0, 22.5, 23.75, 26.25, 27.5 30 and $35^{\circ}C$. The results of velocity vectors and contours have been represented for various parameters. Based on the numerical data, the relationships between temperature difference and flow rate into room was represented. In the case of $T_\gamma>T_\omega$, the equation for temperature difference and flow rate was $Q=0.0285\triangleT^0.4005$, and in the case of $T_\gamma>T_\omega$, the equation was $Q=0.0099\triangleT^0.4752$. The duct system has an important relation to room temperature and duct wall temperature.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.552-558
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• 1999

Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room numerical simulation with a standard k-$\varepsilon$model was carried out. In the present study the marine engine room is considered as a closed space with a heat source and forced ventilation ducts. The injection angle of air supply is found to be important. Injection with a downward angle depresses recirculation flow causing a strong stream in the wider space of the room Ventilation and removal of the released heat are promoted with this pattern, There is a possibility of local extreme heating at the upper surface of the engine when supply and exhaust ports of air are in bilateral symmetry.

• 설비공학논문집
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• 제1권2호
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• pp.173-181
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• 1989

Until recently there was a lack of reliable performance data for the design and operation of Ondol heating systems. This paper presents a calculation method on heat flux from Ondol floor surface. Total heat flux from floor consists of radiation and convection component. In order to analyse the characteristics of both radiation and convection heat flux, each surface temperature is measured and several temperatures near each wall are measured vertically and horizontally in a practical Ondol heating space. Radiation heat flux is calculated and analysed by Gebhart's Absorption Factor Method with the consideration of instantaneous radiant exchanges. Convection heat output is derived from the vertical temperature profiles near floor. The vertical temperature profiles could be expressed by nonlinear regression equation models and convection coefficients could be estimated by the equations. As a result, radiation, convection and total heat flux are suggested by the expression of difference between floor surface and room air temperature.

• Journal of Biosystems Engineering
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• 제26권4호
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• pp.385-390
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• 2001

The Ondol system using both air-to-water heat pump and PCM(Phase Change Material) was constructed, and the effects of ambient air temperature on COP(Coefficient of Performance) of heat pump, the amount of heat supplied to the Ondol in the heating process, the heat storage in the PCM and the variation of Ondol room temperature were analyzed. The results from this study could be summarized as follows: 1. The COP of the heat pump (3 PS) was in proportion to the ambient air temperature. 2. When the ambient air temperature was varied between -10$^{\circ}C$ and -7$^{\circ}C$, the air temperature in the Ondol room was maintained between 16$^{\circ}C$ and 22$^{\circ}C$. As the results, it was certified that the heat pump-latent heat storage type Ondol system could be a comfortable residential heating system in the winter. 3. The maximum radiation and convection heat transfer from Ondol surface was 206.2 kJ/㎥hr and 82.6 kJ/㎥hr respectively. As the results, it could be confirmed that the radiation was major heat transfer mechanism for the Ondol room heating.

• 태양에너지
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• 제18권1호
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• pp.91-98
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• 1998

밑면이 가열되고 다양한 격판을 가진 실내공간에서의 혼합대류 열전달을 유한체적법을 사용하여 연구하였다. 본 연구에서 사용된 변수는 50$\overline{Nu}=\overline{Nu_n}{\cdot}(1+c(Re/Gr^{1/2})^d)$로 나타낼 수 있다. 여기서 $\overline{Nu_n}$는 순수 자연대류를 나타낸다.

• 한국주거학회논문집
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• 제10권4호
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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.

• 설비공학논문집
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• 제7권2호
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• pp.287-297
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• 1995

In this study, the geometry consists of a two-dimensional rectangular enclosure with localized heating from below. The size and the location of the heater on the floor has been varied, and one of the vertical walls remains at a low temperature simulating a cold window. The governing equations for momentum, energy and continuity, which are coupled with turbulent equations have been solved using a finite volume method. A low Reynolds number $k-{\varepsilon}$ model has been incorporated to solve the turbulent kinetic energy and the dissipation rate. The heat transfer characteristics and the thermal environmental characteristics of the room have been obtained for various system parameters in a room with a partially heated floor.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.425-430
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• 2019

아연말 코팅은 친환경성 및 고성능으로 인하여 널리 사용되고 있다. 일반적으로 코팅온도가 코팅층 두께 및 코팅 품질을 결정하는 주요한 요소이며 아연말 코팅의 경우에도 코팅 룸 내 균일하며 적절한 코팅온도가 요구된다. 본 연구에서는 일반적으로 사용하는 자연대류 상태에서의 아연말 스프레이 코팅 룸의 온도 분포를 해석하기 위해 룸 내부의 공기 유동을 포함하는 열 유동 전산 시뮬레이션을 수행하였다. 3차원 CAD 프로그램인 SolidWorks를 이용하여 스프레이 코팅 룸 전체와 예열실과 건조실을 모두 고려한 모델링을 수행하였으며 ANSYS의 FLUENT 프로그램을 이용하여 열 유동연성 해석을 수행하였다. 해석 결과 스프레이 코팅 룸에서의 온도 분포 특성을 파악할 수 있었으며, 현재의 상태로는 목표 온도 값인 $25^{\circ}C$에 미달하고 있었음을 알 수 있었다. 이에 두 가지 다른 경계조건 (히터를 추가하는 방법과 현재 상태에서 Open 부분을 닫는 방법) 에 대해 열 유동 시뮬레이션을 수행하였으며, 시뮬레이션 결과 히터를 추가하기보다는 Open된 부분을 닫는 방법이 더 좋은 결과를 나타내었다.

• 대한설비공학회지:설비저널
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• 제14권3호
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• pp.200-211
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• 1985

The paper discusses the problem of the reduction in Coefficient of Performance (COP) in a refrigerator due to the inadequate position or some flow obstacles such as shelves in a room. The propriety of the present numerical method has teen proved by experiments using the flow visualization technique. The COP are calculated from the temperature rise of the condenser whose temperature indicates the condensing temperature of refrigerant The temperature rise is predicted by the theory of the steady two-dimensional laminar natural convection. In a room size of $2m\;{\times}\;2m$ the COP are decreased by 0.3 when the gap between the wall and condenser are decreased from 10cm to 2cm. While the COP are decreased by 0.55 as the shelf length increases from 0 to 75cm.