Temperature distribution in a naturally ventilated venlo greenhouse with six spans and high eaves: A wind tunnel study
2000
Okushima, L. (National Research Inst. of Agricultural Engineering, Tsukuba, Ibaraki (Japan)) | Sase, S. | Maekawa, T. | Ikeguchi, A. | Bailey, B.J.
This paper presents a wind tunnel investigation of the temperature distributions in a naturally ventilated, multispan Venlo greenhouse. The tests were carried using a model of 1:12 scale with simulated tomato vegetations 0, 1 and 2 m high at full scale, simulated ground heating and external wind speeds of 0 to 3.9 m.s(-1). Similarity conditions were applied for conservation of the archimedes number. The air temperatures, measured by thermocouples, with no canopy were higher on the windward side of the greenhouse than on the leeward side for all wind speeds. The results showed that a re-circulating air flow occurred, even when the wind speed was zero. One of the causes may be a very small difference in the floor temperatures. At wind speeds below 1 m.s(-1), the spatial average air temperature inside the greenhouse, except near floor, wall and roof, was almost independent of wind speed. As the wind speeds increased above 1 m.s(-1) the average internal air temperature decreased. The highest air temperatures occurred when the wind speed was around 1 m.s(-1). The air temperatures at the mid-height of the greenhouse with a simulated 1 m-high canopy were lower than without the vegetation, however, the air temperatures below 1 m were higher. In the free space above the canopy a large weak re-circulating flow existed, similar to that which occurred in the whole house when no plants were present. Heat release from the 2 m-high plants into the free space above the canopy seemed to be less than that with a 1 m high canopy. However, the heat release to the paths was greater. The upper space was less homogeneous with the 2 m high canopy than with 1 m canopy
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