선택한 단어 수는 입니다.
최소 단어 이상 선택하여야 합니다.
최소 단어 이상 선택하여야 합니다.
선택한 단어 수는 30입니다.
최대 10 단어까지만 선택 가능합니다.
최대 10 단어까지만 선택 가능합니다.
제안 방법
- U values were also similar under simulated night sky radiation: under outdoor conditions the coefficient was 1 %, 3 %, and 4 % higher than that measured in the indoor experiment for the 1 L, 2 L, and 3 LM treatments, respectively; values were equal for 4 LW and 7 % lower for 4 LM. Because the differences between the experiments were small, the experimental device used in this study can be considered reliable for measuring U values, and overall heat transfer coefficients can be obtained in a laboratory setting using a night sky radiation simulator. These results demonstrate the feasibility of measuring the U values of greenhouse covering materials and thermal screens with indoor experiments.
- In terms of quantity of heat loss, differences in U values was greater for covering treatments with higher U values, and decreased as the temperature difference between the inside and outside of the hot box increased. Because the differences between the inside and outside experiments were small, the experimental device used in this study can be considered reliable for measuring U values, and overall heat transfer coefficients can be obtained in a laboratory setting using a night sky radiation simulator. These results demonstrate the feasibility of measuring the U values of greenhouse covering materials and thermal screens with indoor experiments.
- Four combinations of thermal screens were tested in the two-layer covering treatments: (1) one layer of multilayer screen; (2) two layers of white polyester; (3) one layer of white fabric polyester and one layer of white polyester; and (4) two layers of multilayer screen. Experiments were conducted to determine U values for each of the four treatments with and without simulated night sky radiation. The temperature in the hot box was set to 10°C, 20°C, 30°C, 40°C, and 50°C.
- Table 2 lists the test materials and treatment conditions used to determine U values in indoor experiments. Experiments were conducted using 12 treatment conditions consisting of various combinations of covering materials and thermal screens and the presence or absence of simulated night sky radiation. One-or two-layer coverings were created with 0.
- 1-mm-thick PE film. Four combinations of thermal screens were tested in the two-layer covering treatments: (1) one layer of multilayer screen; (2) two layers of white polyester; (3) one layer of white fabric polyester and one layer of white polyester; and (4) two layers of multilayer screen. Experiments were conducted to determine U values for each of the four treatments with and without simulated night sky radiation.
- 5 shows the location of surface and air temperature sensors. Heat loss through the hot box walls was calculated by measuring the inner and outer surface temperature of three walls using a UE-1530 sensor (USEEM, Korea) equipped with a ZFRM data logger (USEEM, Korea). External wind speed was measured every 10 min, outside and inside the indoor cold chamber, with a Kestrel 4500 wind gauge (Nielsen-Kellerman, USA).
- In this research, U values of greenhouse covering materials with thermal screens commonly used in Korea were investigated using a hot box under ambient outdoor climatic conditions and in a laboratory system in which night sky radiation was simulated. U values measured at high wind speeds in outdoor experiments were greater than those measured at low wind speeds for all treatments.
- Many researchers show the relationship of the overall heat transfer coefficient and the wind speed as a linear relationship (Hanan, 1998). The results are analyzed by inducing the linear formula in this study. The variation of U values according to the temperature difference between the inside and outside of the hot box increases as the wind speed increases.
- 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.
- Temperatures at various locations inside and outside the hot box were measured using six HOBO temperature sensors (Onset, USA), and average values were calculated. Two additional temperature sensors were installed outside the hot box and their values were averaged to increase the accuracy of the measurements. The temperature at each compartment of the experiment was set via a connection to an on–off controller.
대상 데이터
- The temperature at each compartment of the experiment was set via a connection to an on–off controller. Experiments were carried out from November 2011 to April 2013.
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