• 한국환경과학회지
• /
• 제6권6호
• /
• pp.579-588
• /
• 1997

In order to see the stratification related to the heat flux In Deukryang Bay, the oceanographic data on July 12, 1994 and the meteorological data of Kohung and Kwangju meteorological stations were analysed. The temperature durerences between the sea surface and the near bottom were 1~3 ton spring tide (July 12, 1994) In Deukryang Bay. The temperature anomalies were high about 3t during summer In 1994. These mean that the non mixing was not effective In destroying the stratification due to the sea surface heating by the solar radition, even though it was on spring tide. The maximum solar radiation was about 600 ly/day, which was the value of the same date of oceanographic observation. The sensible and the latent heat flux which are 0~100 ly/day were not so varied during summer. The absorbed heat flux through the sea surface was mostly lost by the back radiation. which ranges are about 0~-400 ly/day. The dimensionless mixing parameter related to the buoyancy flux was 5~150$\times$$10^{-5}$. The efficiency of tidal mixing to destroy the stratecation was 0.4~0.6%.

• 한국안전학회지
• /
• 제17권3호
• /
• pp.56-60
• /
• 2002

The purpose of this study was to present the thermal characteristics of the working uniform exposed to the radiation heat. The effect of exposure time and exposure distance on the changes and the relationship between physical properties were investigated experimentally. Regardless of the kind of working uniform, the surface temperature of the working uniform with exposed time sharply increases as exposed distance is more close and the reaching time of steady state is shorter. The surface temperature of working uniform exponentially decreases as exposed distance become more distant. For the safety of the working man, it is necessary that he work far away at a fixed standard distance from the radiant heat source.

• 대한기계학회논문집
• /
• 제18권5호
• /
• pp.1288-1300
• /
• 1994

Mathematical modeling and numerical calculation on the flow and thermal characteristics induced by fire in a partial enclosure are performed. The solution procedures include the Shvab-Zeldovich approximation for the physical transport equations, low Reynolds number k-.epsilon. model for the turbulent fluid flow and Discrete Ordinate method(DOM) to calculate the radiative heat transfer. PMMA(Polymethylmethacrylate) is adopted as a solid fuel. Two different cases are considered : combustions with and without gas radiation occuring in a open cavity for variable pyrolyzing location of PMMA. When the fire source is located at the left-wall, the flow region of flame gas is limited at the left-wall and ceiling and recirculation region of inlet gas is formulated at neat the floor. In case of neglecting the radiative heat transfer, more large flame size and higher temperature is predicted. It is essential to consider the radiative heat transfer for analysis of fire phenomenon.

• Nuclear Engineering and Technology
• /
• 제49권8호
• /
• pp.1654-1659
• /
• 2017

The boundary layer of a two-dimensional forced convective flow along a persistent moving horizontal needle in an electrically conducting magnetohydrodynamic dissipative nanofluid was numerically investigated. The energy equation was constructed with Joule heating, viscous dissipation, uneven heat source/sink, and thermal radiation effects. We analyzed the boundary layer behavior of a continuously moving needle in Blasius (moving fluid) and Sakiadis (quiescent fluid) flows. We considered Cu nanoparticles embedded in methanol. The reduced system of governing Partial differential equations (PDEs) was solved by employing the Runge-Kutta-based shooting process. Computational outcomes of the rate of heat transfer and friction factors were tabulated and discussed. Velocity and temperature descriptions were examined with the assistance of graphical illustrations. Increasing the needle size did not have a significant influence on the Blasius flow. The heat transfer rate in the Sakiadis flow was high compared with that in the Blasius flow.

• 대한기계학회논문집
• /
• 제14권3호
• /
• pp.685-693
• /
• 1990

본 연구에서는 복사열전달 효과를 알아보기 위해 에너지 방정식을 수치적으로 풀었으며, 그 결과를 열전달계수 및 온도의 항으로 나타내었다. 수치 해석적 모델의 검증을 위해 여러사람들이 물질전달과정 해석을 위해 사용한 나프타린 승화법(naphth- alene sublimation technique)을 이용하여 실험을 수행하였다. 또한 실험에 사용된 다공질체(ceramic blocks)의 침투율도 측정하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2007년도 추계학술대회 논문집
• /
• pp.505-510
• /
• 2007

Greenhouses should be heated during nights and co Id days in order to fit growth conditions in greenhouses. Ground source heat pump(GSHP) or geothermal heat pump system(GHPs) is recognized to be outstanding heating and cooling system. Horizontal GSHP system is typically less expensive than vertical GSHP system but requires wide ground area to bury ground heat exchanger (GHE). In this study, a horizontal GSHP system with thermal storage tank was installed in greenhouse and investigated as performance characteristics. In the daytime, heating load of greenhouse is very small or needless because solar radiation increases inner air temperature. The results of study showed that the heating coefficient of performance of the heat pump($COP_h$) was 2.9 and the overall heating coefficient of performance of the system($COP_{sys}$) was 2.4. Heating energy cost was saved 76% using the horizontal GSHP system with thermal storage tank.

• Journal of Biosystems Engineering
• /
• 제19권3호
• /
• pp.211-221
• /
• 1994

In this study, to maximize the solar energy utilization for greenhouse heating during the winter season, solar energy-underground latent heat storage system was constructed, and the thermal performance of the system has been analyzed to obtain the basic data for realization of greenhouse solar heating system. The results are summarized as follows. 1. $Na_2SO_4{\cdot}10H_20$ was selected as a latent heat storage material, its physical properties were stabilized and the phase change temperature was controlled at $13{\sim}15^{\circ}C$. 2. Solar radiation of winter season was the lowest value in December, and Jinju area was the highest and the lowest value was shown in Jeju area. 3. The minimum inner air temperature of greenhouse with latent heat storage system(LHSS) was $7.0{\sim}7.5^{\circ}C$ higher than that of greenhouse without LHSS and was $7.0{\sim}11.2^{\circ}C$ higher than the minimum ambient air temperature. 4. Greenhouse heating effect of latent heat storage system was getting higher according to the increase of solar radiation and was not concerned with the variation of minimum ambient air temperature. 5. The relative humidity of greenhouse with latent heat storage system was varied from 50 to 85%, but that of greenhouse without LHSS was varied from 30 to 93%. 6. The heating cost of greenhouse with solar energy-latent heat storage system was about 24% of that with the kerosene heating system.

• 설비공학논문집
• /
• 제7권4호
• /
• pp.611-621
• /
• 1995

The objectives of this study are to find out and to analyze the heat transmission characteristics of the conventional and prefabricated Ondol systems. To compare the thermal characteristics of these Ondol, a real sized Ondol model is set in a chamber. Hot water whose temperature is varied from $45^{\circ}C$ to $60^{\circ}C$ with $5^{\circ}C$ interval is supplied to each Ondol system. At that time the temperature distribution of floor surface, the amount of supplied heat, the heat radiation aspect and the heat loss from the floor to the underground are measured and analyzed simultaneously. As a result, even if the supplied hot water temperature to the prefabricated Ondol panel is lower by about $5^{\circ}C$ than that of the conventional Ondol panel, the net radiant effect is same. Heat radiation efficiency of the prefabricated Ondol panel is over 5% better than that of the conventional Ondol panel. It takes 12 hours for the conventional Ondol and 45 minutes for the prefabricated Ondol, respectively to reach steady state.

• 한국수자원학회논문집
• /
• 제46권2호
• /
• pp.111-122
• /
• 2013

최근 들어 기후변화로 인해 물과 에너지 순환에 관한 정확한 이해가 요구되고 있다. 현재 미기상학적 플럭스 타워 네트워크는 수문학적, 생태학적 분석에 있어서 주춧돌역할을 하고 있다. 하지만 플럭스 타워의 에디공분산 방법을 활용한 잠열 플럭스 측정은 여러 가정사항에 따른 시스템적 오류를 내포하고 있고 이에 따라 과소평가된 잠열 플럭스 원시자료의 보정이 필요하다. 몇몇의 보정방법 중 보엔비를 활용한 방법이 가장 유용한 방법 중 하나로서 여기에는 플럭스타워에서 측정한 순 복사에너지 및 기타 플럭스(현열, 지열) 등이 요구되며 이러한 자료에 대한 정확한 측정 및 검증이 필요하다. 본 연구에서는 설마천, 청미천 유역의 플럭스타워에서 측정된 순 복사에너지를 검증하기 위해 두 가지 형태의 이론적으로 계산된 순 복사에너지와의 비교검증을 실시하였다-(1) FAO 56 기반의 일평균 순 복사에너지 (2) Bastiaansen (1995)가 제안한 순간 순 복사에너지. 본 연구의 결과는 플럭스타워에서 측정된 순 복사에너지는 이론적으로 계산된 순 복사에너지와 상당히 비슷한 경향성을 보인다는 것을 제시했다. 또한, 측정된 순 복사에너지를 이용하여 관측된 잠열플럭스를 보엔비 보정방법에 적용시킨 결과 에너지수지에 더욱 부합하는 것을 알 수 있었다.

• International Journal of Aeronautical and Space Sciences
• /
• 제14권2호
• /
• pp.105-111
• /
• 2013

Radiative heating phenomena occurring in planetary entry flights are reviewed for the purpose of educating those who are not familiar with the problem. How the radiative heat transfer rates to the Apollo entry vehicle were measured and analyzed are first described. Next, the effects of thermo-chemical non-equilibrium on radiation are summarized. Then the radiation problems in entry flights into other planets are reviewed. Finally, unsolved problems are enumerated.