Theoretical study of natural ventilation flux in a single span greenhouse

Abstract

The ventilation flux was calculated for single span greenhouses with single longitudinal roof opening and with bothlongitudinal roof and vertical side wall openings. Thermal buoyancy and wind pressure contributions were separatelyanalysed and then combined for lee-side as well as for windward side ventilation.For the single roof window, the temperatureeffect, proportional to the square root of the temperature difference, becomes negligible when compared to the wind effect,proportional to the wind speed, as soon as this is higher than 1.5 m.s-1.When a vertical side wall opening was added to theroof window, the temperature effect was enhanced by the so called chimney effect, linked with the vertical distance betweenthe two openings, in such a way that it becomes negligible only for an external wind speed higher than 4 m.s-1.

Keywords

• Greenhouse
• natural ventilation
• wind and temperature effects