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Volume 40 (2009)
- Issue 4 Pages 219-
- Issue 3 Pages 159-
- Issue 2 Pages 113-
- Issue 1 Pages 1-
Volume 40, Issue 2
Vol. 40, No. 2 (Ser. No. 122)
Displaying 1-4 of 4 articles from this issue
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Shinsuke FURUNO, Sadanori SASE, Hironori SATO2009 Volume 40 Issue 2 Pages 113-120
Published: 2009
Released on J-STAGE: December 14, 2023
JOURNAL OPEN ACCESSThe measurements of heating load and heating degree hour (DH) of several plastic greenhouses in Yamagata were carried out in the heavy snowfall winter from 2005 through 2006. Based on the measured oil consumption and weather data, the results can be summarized as follows: (1) In all measured plastic greenhouses, the heating load was proportional and significant to DH. However, if the greenhouse floor was not covered with plants or weeds, the regression line did not cross the origin and its intercept was minus. This shows that the heating load was decreased by the soil heat flux which was caused by solar radiation. On the other hand, if the floor surface of plastic greenhouse was covered with plants or weeds, the regression line generally crossed the origin. This shows that solar radiation did not reach to floor and there was little soil heat flux. (2) Average heating load coefficient of all measured plastic greenhouses in snowy area was smaller than proposed coefficient (5.0 W m-2 ℃-1) based on the measurement in kanto area. In snowy area, if DH was large and measuring time of period was long, average heating load coefficient should be around 4 W m-2 ℃-1.View full abstractDownload PDF (2371K) -
- Effects of side-wall openings on load effects -Yasushi UEMATSU, Koichi NAKAHARA, Hideki MORIYAMA, Sadanori SASE2009 Volume 40 Issue 2 Pages 121-131
Published: 2009
Released on J-STAGE: December 14, 2023
JOURNAL OPEN ACCESSWind loads on pipe-framed greenhouses can be reduced by making the sidewalls porous. Wind pressures on the external and internal surfaces of two 1:40 scale models of pipe-framed greenhouses with porous sidewalls are measured simultaneously at many points in a turbulent boundary layer simulating natural winds over typical open-country exposure for various wind directions. Wind speeds at some points inside the greenhouse are also measured. The porosity of the windward and leeward sidewalls is changed over a wide range. The wind loads represented by equivalent static wind force coefficients are evaluated by using the LRC (Load Response Correlation) method, in which the bending moment at the windward column base is taken into account as the most important load effect. The effects of the porosity on the wind loads and responses of the frame as well as on the wind speeds inside the greenhouse are investigated. The results indicate that the porosity of 0.3-0.5 can reduce the maximum bending moment by 15 to 20 percent. In such a case, the wind speed becomes approximately 40 percent of the outside wind speed. Finally, the subjects to be investigated for applying the results of the present study to practical structures are summarized.View full abstractDownload PDF (2887K) -
Digui YANG, Kazuhiro NAKANO, Daisuke TERANO, Haijun YAN, Shintaroh OHA ...2009 Volume 40 Issue 2 Pages 133-142
Published: 2009
Released on J-STAGE: December 14, 2023
JOURNAL OPEN ACCESSThe microclimate inside a group of four single-span greenhouses, with a narrow space between two adjacent greenhouses, was numerically analyzed using a Computational Fluid Dynamics (CFD) package under different wind conditions. First, three-dimensional simulations were validated through experimental measurements. Good agreement was obtained between the experimental and numerical results. Second, simulations were carried out under steady-state conditions. The air exchange rate and temperature distribution under various wind speeds and directions were analyzed based on the numerical results. The results showed: a) with the same outside wind speed and direction, the air exchange rate of the greenhouses was strongly affected by their relative location to the wind direction according to whether they were windward or leeward; b) there was a shelter effect for the air temperature inside greenhouses that were leeward to the wind direction; and c) the buoyancy effect played an important role in the calculation of the air exchange rate of greenhouses when the outside wind speed was lower than 1 m/s, but the air exchange rate had almost a linear relation to the outside wind speed when it was higher than 2 m/s, which meant the buoyancy effect resulting from the temperature difference was negligible.View full abstractDownload PDF (2837K) -
Yuta OGUCHI, Yutaka KITAMURA, Takashi FUJIEDA, Wei Zhong JIANG2009 Volume 40 Issue 2 Pages 143-148
Published: 2009
Released on J-STAGE: December 14, 2023
JOURNAL OPEN ACCESSUsing of organic wastewater with low C/N-ratio, characteristics of hydrogen fermentation were investigated and its applicability to the hydrogen/methane two-stage fermentation was elucidated experimentally. Glucose and peptone were used as substrates of the synthetic wastewater with 4.9 C/N-ratio. The hydrogen yields from 0.41 to 0.44 mol-H2/mol-glucose were not different significantly at 0.5, 1.0 and 1.5 % of the substrate concentration. The VHPR (Volumetric Hydrogen Production Rate) was maximal of 2.13 L/L-d at 1.5 % of the substrate concentration. However the yield and VHPR were decreased significantly at 2.0 % of the substrate concentration. In the substrates the carbon was almost consumed while the excess nitrogen was not converted to ammonia in the reactors. The experimental growth constants and kinetic parameters showed the higher activity of the hydrogen fermentation and the shorter HRT operation at 2.6 h than the conventional acidogenic fermentation. The two-stage fermentation was concluded to apply to the treatment of organic wastewater with low C/N-ratio without ammonia inhibition.View full abstractDownload PDF (1853K)
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