Influence of an insect screen on greenhouse ventilation
The influence of an insect screen on ventilation rate was experimentally investigated in a multispan glass-covered greenhouse equipped with a continuous roof vent, located at the University of Thessaly near volos in the coastal area of eastern Greece. Microclimate variables as well as the ventilation rate were measured during summer. Two measuring techniques were used for the determination of ventilation rate: (1) the decay rate tracer gas technique, using N2O as tracer gas, and (2) the water vapor balance technique. The influence of the insect screen on ventilation rate was studied using a wind-related coefficient identified by fitting a simple linear model to the experimental values. The two measuring techniques gave similar results, but the water vapor balance technique provided a better fit to the experimental data. The wind-related coefficient significantly decreased when an insect screen covered the vent. Finally, the influence of the insect screen on the discharge coefficient was investigated. The discharge coefficient was correlated to the aerodynamic properties of the screen using porous media flow analysis.