Analysis of ventilation characteristics for prevention of high temperature inside a commercial greenhouse

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In order to investigate the cause that the ventilation rate of large-scale Venlo greenhouse with roof ventilators and without side wall ventilators is smaller than that of conventional greenhouse with roof and side wall ventilators, the following measurements were done.1.In the case of total open area of ventilators (roof ventilators + side wall ventilators) was the same, the influence of open area of side wall ventilators on ventilation rate of the greenhouse was tested with single span greenhouse. As a result, in the spite of open area of ventilators was the same, the ventilation rate with side wall and roof ventilators opened was 1.5-5 times that with roof ventilators opened. These results suggested that the chimney effect is promoted by side wall ventilators.2.In order to investigate the influence of side wall ventilators on the inside temperature distribution and ventilation rate of the large-scale Venlo greenhouse, environmental measurement was done with medium-scale Venlo greenhouse which was equipped with side wall ventilators. It assumed that the medium-scale Venlo greenhouse was the part of the large-scale Venlo greenhouse, so the one side wall ventilators were opened in the measurement. Temperatures near the side wall decreased when side wall ventilators were opened, and the ventilation rate of greenhouse calculated by the heat balance method increased near the ventilators. However the range of the influence of side wall ventilators on environments inside the Venlo greenhouse was about 20m from the side ventilators.From these results, side wall ventilators promote the ventilation rate of the greenhouse, however the influence is decreased as departing from the side wall to central part in the large-scale Venlo greenhouse.