Impact van een schermkier boven het middenpad bij een Ventilationjet systeem

Between growers there is discussion if a (controllable) gap above the central path of the greenhouse is needed toextract the surplus of heat and vapour in a greenhouse equipped with artificial lights and Ventilation Jets. Basedon this discussion, this research was started at a tomato greenhouse with artificial lights to analyse the impactof this gap. To determine the effectiveness of this gap, the air flow through the Ventilation Jet was measuredwith an air flow measurement device, the air flow through the gap at the central path was determined usingair velocity sensors and horizontal temperature differences were measured with wireless temperature sensors.Based on this study we can conclude that: (1) at this grower the measured flow of the Ventilationjet at 2 closedscreens (6.7 m3/m2/hour) was much lower than expected (12 m3/m2/hour); (2) the impact of the gap at thecentral path was small (a maximum of 2.8% of the incoming air through the Ventilation Jets left the greenhousethrough this gap), the gap at this grower is this not needed since almost all air leaves the greenhouse throughthe screens and; (3) in case that the artificial lights were switched on and both screens were closed, largehorizontal temperature differences of maximum 2.7°C occurred