Ventilation of small multispan greenhouse in relation to the window openings calculated with CFD

Ventilation is the most important aspect for the climatization of greenhouses. Heat, moisture, and CO2 are removed through ventilation. The effect of the dimensions of the ventilation windows and the orientation to the wind are investigated for a summer condition for a greenhouse design with a crop. Calculations are done using computational fluid dynamics (CFD). The ventilation rate and the temperature distribution in the greenhouse are compared for the different ventilation openings. The influence of wind direction is determined at 5 m s(-1) windspeed together with the situation when no wind is present. The results show a large temperature gradient in the greenhouse. This gradient can be explained from the fact that the heat input is high causing a substantial temperature difference between the greenhouse air and the ambient. Ventilation increased as the window opening increased as expected. Opening only the window on the windward side resulted in almost double the ventilation than opening both the leeward and windward orientated windows. Side ventilation increases the ventilation especially when no wind is present.