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- 저자 : 나욱호 ( O. H. Na ) (검색결과 3 건)
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핫박스를 이용한 플라스틱온실 피복재 및 보온재의 열적 성질 측정
소레이멘디옵 ( S. Diop ),이종원 ( J. W. Lee ),나욱호 ( O. H. Na ),신동창 ( D. C. Shin ),이현우 ( H. W. Lee ) 한국농공학회 2012 한국농공학회 학술대회초록집 Vol.2012 No.-
Recent increases in fuel prices have forced growers to apply energy-saving measures in their heated greenhouses. As a result, growers have been forced to consider innovative cover materials and they have been advised to install thermal screens. Materials used as greenhouse covers are not spatially homogeneous that’s why the selection of a covering is crucial for attainment of an optimal controlled environment. Several attempts have been already made to develop measurement procedures applicable under conditions resembling those of greenhouse production on purpose to investigate the U-values of glazing materials by using a hot box. The objective of the present study was to investigate the overall heat transfer coefficient of greenhouse covering materials with or without thermal screens commonly used in the country under external and real conditions by using the hot box method. For this research we designed and built a guarded hot box partially based on ASTM standards C 236-89. The technique used in the present work was inspired by work using guarded hot box (Feuilloley et al., 1996) to investigate the overall heat transfer coefficient of different greenhouse covering materials with thermal screens widely used in the country. The test conditions of eight treatments combined covering materials and thermal screens with and without shelter from the sky radiation were used to determine the overall heat transfer coefficient. The insulation effect of two layers covering material is about 28% comparing to one layer covering material and the coefficient is 2.4 (W·m<sup>-2</sup>·K<sup>-1</sup>)less than one layer. The coefficients obtained under the high wind speed were 6∼14% greater than those under the low wind speed. The decrease of the coefficient of one layer and two layers coverings by shelter was about 20% and 30% respectively. When we measure the overall heat transfer coefficients in a laboratory, it is necessary to establish the measuring system to be able to simulate the sky radiation.
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실내실험에 의한 온실 피복재 및 보온재의 관류열전달계수 측정
소레이멘디옵 ( S. Diop ),이종원 ( J. W. Lee ),나욱호 ( O. H. Na ),신동창 ( D. C Shin ),이현우 ( H. W. Lee ) 한국농공학회 2013 한국농공학회 학술대회초록집 Vol.2013 No.-
To optimize the heating system, it is necessary to assess the actual energy saving potential of new covering systems as they are introduced into markets. Many studies have been conducted to reduce energy consumption for greenhouse heating and suggest an overall heat transfer coefficient. However, the coefficients suggested vary greatly because the covering material characteristics, climate conditions and greenhouse environments differ. Accordingly, modification of existing testing methods is required because, in most cases, they are insufficient for greenhouse covering materials. As a result, further studies using the hot box method to determine the thermal transmittance of various greenhouse covering materials have been conducted. This study is conducted by producing an indoor experimental apparatus for measuring the overall heat transfer coefficient with which the actual sky temperature can be implemented and measuring greenhouse coverings and thermal screens available in Korea to compare the results with the measured results in the outdoor experiment and to assess their appropriateness. Experiment is carried out for 12 kinds of treatment conditions according to combination of covering materials and thermal screens and whether there is sky thermal radiation or not. The measuring results show that the overall heat transfer coefficient increases almost straightforward proportionally as the difference in temperature for all of test covering treatments increases in case that sky thermal radiation is not implemented. And in case that sky thermal radiation is implemented the overall heat transfer coefficient becomes the highest when the difference in temperature between inside and outside of the hot box is 10℃ and is significantly lowered when the difference in temperature becomes near 20℃ and after that, there is no significant change and the overall heat transfer coefficient maintains almost constant as the difference in temperature becomes higher than 20℃. Even though slight differences between the indoor experiment results and the outdoor experiment results are shown, they are in accord with the range of standard deviation of the indoor experiment results. These results show that it is reasonable to measure the overall heat transfer coefficient of greenhouse covering materials and thermal screens through the indoor experiment.
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