Abstract
This paper presents a wind tunnel investigation of the temperature distributions in a naturally ventilated, multi-span Venlo greenhouse. The tests were carried using a model of 1:12 scale with simulated tomato vegetations 0, 1 and 2m high at full scale, simulated ground heating and external wind speeds of 0 to 3.9m·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 1m·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 1m·s-1 the average internal air temperature decreased. The highest air temperatures occurred when the wind speed was around 1m·s-1.
The air temperatures at the mid-height of the greenhouse with a simulated 1m-high canopy were lower than without the vegetation, however, the air temperatures below 1m 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 2m-high plants into the free space above the canopy seemed to be less than that with a 1m high canopy. However, the heat release to the paths was greater. The upper space was less homogeneous with the 2m-high canopy than with 1m canopy.
